Air quality in transportation cabins--Part I: how much do we know about it?

ABSTRACT

Recent field studies of the air quality in transportation cabins are summarized in this paper. Overall, very limited field data are available to the public. A comparison of the methodologies showed that no common instrumentation was used in the field measurements, even for identical indoor air quality parameters. Therefore, care should be exercised when comparing the results from different studies. Most of the air contaminant concentrations in airplanes were below the threshold values during cruising and in nonsmoking environments but could reach higher levels for noncruising periods and smoking environments. The air quality in passenger vehicles varied significantly with the ventilation mode, weather, and traffic. In summary, there were limited field data available in ground transportation cabins, and no data have been reported for commercial truck cabins.

INTRODUCTION

Over the past few decades, there has been increasing interest in the air quality in transportation cabins, including airplanes and ground transportation. Similar to other indoor environments, in-cabin air quality is also dependent on temperature, relative humidity, and the concentrations of airborne contaminants. These parameters could have significant effect on the health and well-being of the occupants.

Temperature and humidity have direct impact on the thermal comfort and the performance of the occupants. The health effects of low humidity include fatigue, headaches, irritated and itchy skin, itchy or irritated eyes, stuffy and even bleeding noses, as well as impaired lung function (Spengler and Wilson 2003). Reinikainen and Jaakkola (1992) found that the dryness of skin and mucosa, allergic reactions, and the sensation of dryness were decreased by air humidification. For a sedentary person, a 30% change in relative humidity (RH) had the same effect on thermal balance and thermal sensation as a 2[degrees]F (1[degrees]C) change in temperature. In warm conditions, thermal discomfort increased with humidity (Berglund 1998). In many hot and humid climates, conventional air-conditioning units were unable to meet the latent load and, consequently, the indoor relative humidity exceeded the recommended value of 60% to 70% RH (ASHRAE 1992). Increasing outdoor ventilation without properly controlling the indoor humidity may actually decrease occupant comfort and perceived air quality (PAQ). This is because excessively low or high humidity may result in excessive evaporation from the skin and respiratory tract (Fang 1998; Simonson et al. 2002; Dowing and Bayer 1993; Toftum and Jorgensen 1998). The total heat loss affects driver performance and, therefore, road safety. The sectional heat loss determines occupant comfort, draft sensation, and the risk of cold-related muscular injury (Wyon et al. 1989).

Temperature and RH also affect PAQ. A recent study showed that the air was perceived as less acceptable with increasing temperature and humidity (Fang 1998). This impact was found to decrease with an increasing level of air pollution. When the temperature and humidity increased through a range of 18[degrees]C to 28[degrees]C and 30% to 70% RH, subjects' satisfaction decreased, and they felt more and more uncomfortable. At any given temperature, a decrease in humidity usually results in the occupants feeling cooler, drier, and more comfortable. In addition, fabrics feel smoother and more pleasant, and the air is perceived to be fresher, less stale, and more acceptable.

Temperature and relative humidity also affect the airborne level of microorganisms (e.g., molds and bacteria), which can cause many acute diseases, infections, and allergies. Microorganisms have different properties at various levels of temperature and humidity. They are well protected indoors by the moisture surrounding them at a relative humidity of 70% or higher. Virus survival is inversely proportional to the RH level and temperature (Akers et al. 1966). The half-lives of viruses range from about two hours at an ultra-high RH and 35[degrees]C to more than seven days at a low RH and 5[degrees]C (Mbithi et al. 1991).

Typical indoor airborne contaminants in a transportation cabin include particulate matter (PM), carbon monoxide (CO), carbon dioxide (C[O.sub.2]), and nitrogen dioxide (N[O.sub.2]). While fine particles are responsible for many respiratory syndromes, ultra-fine particles and nanoparticles pose more threats to indoor occupants because they can penetrate deeply into the respiratory system. The nanoparticles from engine exhaust can translocate from the lungs to the brain and blood, thereby causing an increase in blood coagulatory and inflammatory effects (The Royal Society 2003; Dreher 2004). PM can also cause irritation and dryness of the eyes and nose, as well as other allergenic responses (Hauschildt et al. 1996; Pan et al. 1999). Furthermore, PM can act as a transport vehicle for other airborne contaminants (Tan and Zhang 2003). These passenger contaminants include gaseous pollutants, viruses, bacteria, organic substances, and odors. Particulates generated by the internal combustion process have also been shown to be associated with increased hospital admissions, decreased lung function in children, and increased risk of acute respiratory infections (ARI) in young children. Exposure to combustion products has been identified as a risk factor for ARI, which is the leading cause of infant mortality in developing countries and is responsible for the deaths of three to five million children under the age of five each year.

C[O.sub.2] is a colorless and odorless gas. One major source of C[O.sub.2] in a ground transportation vehicle is the emissions from other vehicles that penetrate through the vehicle's ventilation system. Vehicles running at 60 mph will emit about 5.2% of their C[O.sub.2] emissions into the outside air (Rienstra and Rietveld 1996) and are one of the major sources of C[O.sub.2] in the air above the road, especially under heavy traffic conditions. Other major sources of C[O.sub.2] in vehicles are the occupants in the vehicles. A typical human being produces 18 liters of C[O.sub.2] per hour (Lindgren and Norback 2002). The level of C[O.sub.2] may become very high in a short time if there is insufficient outside air intake and exchange. For example, in a normal office in winter, the ratio of inside and outside concentrations of C[O.sub.2] can reach as high as 8.0 (Baek 1997).

C[O.sub.2] has obvious health effects on humans at various levels. At the concentration of 700 ppm or lower, the adverse effect is negligible, but people will start to feel uncomfortable when the C[O.sub.2] concentration reaches 800 ppm (MDH 2004). In an environment where the C[O.sub.2] concentration reaches 5,000 ppm, people will feel fatigued and lose concentration (OSHA 1995), and at 20,000 ppm they will also breathe at 150% of the normal rate. When the concentration of C[O.sub.2] is increased to 30, 000 ppm, heart rate and blood pressure will increase (Schwarzberg 1993), hearing can be impaired, and most people will feel dizzy.

Carbon monoxide (CO) is a colorless, odorless, and taste-less toxic gas that is generated from incomplete fuel combustion. Engine exhausts contribute to approximately 56% of all CO emissions in the United States. Higher levels of CO in automobile cabins generally occur in areas with heavy vehicle traffic, and, in many cities, 85% to 95% of CO emissions come from motor vehicle exhaust. Emissions of CO from motor vehicles cause several hundred accidental fatal poisonings in the United States annually (Marr et al. 1998), and 57% occur in automobiles. The highest levels of CO in the outside air typically occur during the colder months of the year.

Carbon monoxide poisoning has its most acute toxic effect on organs with high oxygen requirements, which include both the heart and brain. CO is toxic because when it enters the bloodstream, it replaces the oxygen molecules found in the critical blood component, hemoglobin, depriving the heart and brain of the oxygen (Coultas and Lambet 1991). Hence, individuals with ischemic heart disease are at particularly high risk (EPA 1991). The study by Garvey and Longo (1978) also found that fetal development was affected by CO.

It should be noted that the health risks associated with CO exposure depend on both the concentration of CO and the duration of exposure. For example, exposure to 70 ppm for 189 min, 150 ppm for 50 min, or 400 ppm for 15 min can result in similar carboxy-hemoglobin levels of about 10% (Raub et al. 2000). When subjects were exposed to concentrations below 90 ppm for a long time, CO was found to have an adverse influence on their hearts, brains, and children's birth weights. Adverse cardiovascular effects may also be observed among the more susceptible individuals (Dahms et al. 1993), and angina, impaired vision, and reduced brain function may result (Townsend and Maynard 2002). When exposed to 200 ppm of CO, most people experience slight headaches, tired-ness, dizziness, and nausea after two to three hours. At 400 ppm, a frontal headache occurs within one to two hours, and life can be threatened after three hours. At 800 ppm, they experience dizziness, nausea, and convulsions within 45 minutes, are unconscious within two hours, and die in two to three hours. At 1,600 ppm, headache, dizziness, and nausea occur within 20 minutes, and death occurs within an hour.

Nitrogen dioxide (N[O.sub.2]) has a pungent acrid odor. N[O.sub.2] is one of the major emissions from vehicles. On-road N[O.sub.2] concentration is very high, reaching 212 ppb (Riediker et al. 2003). High N[O.sub.2] concentration in a vehicle may result in driver fatigue, lack of concentration, and loss of cognitive ability, reducing the ability of the driver to operate the vehicle safely. Consequently, there may be a link between air quality and transportation safety.

Simoni et al. (2002) showed that there was a close relationship between the indoor N[O.sub.2] levels of 33 ppm in winter and increased occurrence of acute respiratory symptoms in non-smoking adults. At higher N[O.sub.2] levels, bronchitic and asthmatic symptoms were significantly more prevalent. They also reported that these health effects were associated with the duration of the exposure. The same exposure indices were obtained when subjects were exposed to a low dose of N[O.sub.2] (i.e., 10 ppb) for a longer duration (five hours) and to a higher N[O.sub.2] concentration (i.e., 50 ppb) for a short duration (one hour). Exposure to N[O.sub.2] of 200 ppm or greater immediately endangers life. At levels of 50-100 ppm, N[O.sub.2] will impair lung function and irritate the eyes, nose, and throat (Alberts 1994). Moreover, there is evidence that N[O.sub.2] may cause lung damage at concentrations of 300 ppb or higher (Jones 1997; Spengler 1993; Samet and Cushing 1997; Viegi et al. 1992; Frampton et al. 1991). There is also evidence that after exposure to 400 ppb of N[O.sub.2] for one hour, the forced expiratory volumes of asthmatics drop by 19% (Tunnicliffe et al. 1994). In addition, Salome et al. (1996) found a higher risk among a sample of 20 asthmatics when exposed to 600 ppb of N[O.sub.2] over a period of one hour.

Children and the elderly are the most vulnerable to N[O.sub.2]. Samet et al. (1992) studied over 1300 infants aged 18 months and found that exposure to N[O.sub.2], especially in winter, may increase the frequency and severity of upper and lower respiratory diseases. Pilotto et al. (1997) monitored the influence of exposures to N[O.sub.2] among 400 children in elementary schools. Significant increases in sore throats, colds, and absences from school were observed when their exposure to N[O.sub.2] was at hourly peak levels of 80 ppb or higher. The adverse respiratory effects were considered to be at short-term peak levels. Shima and Adachi (2000) focused on 842 children (434 boys and 408 girls) from grades 4 to 6 for over three years. They found that when the annual average indoor N[O.sub.2] concentrations were more than 40 ppb, respiratory symptoms were very prevalent among girls.

In one of the few studies that examined engineering and other environmental effects, Galatsis et al. (2000) linked in-cabin air quality with fatigue and, hence, indirectly with road safety. They found that it was necessary to install gas sensors in an enclosed space. The air quality can then be improved by controlling the ventilation system. When the concentrations of the pollutants monitored are high, an alarm will be activated to inform the occupants to open the ventilation system, thereby keeping the air quality in the cabin as good as the ambient air. Sato (2002) suggested that further studies focusing on the effects of air quality on safe and comfortable driving should be conducted.

A comprehensive review of the literature on in-cabin air quality is thus essential to understand the importance of air quality parameters and their impact on human welfare, health, and the productivity of the vehicle occupants.

The objective of this paper is to establish a basic knowledge of the levels of the air pollutants in various transportation cabins. The methodologies and major findings of these studies were reviewed and compared.

FIELD STUDIES OF IAQ IN TRANSPORTATION CABINS

While numerical and computational tools have been used to study the relative humidity in airplanes (Lindgren and Norback 2002; Spengler and Wilson 2003), this paper will focus only on field measurements in transportation cabins. We found only a few studies of in-cabin air quality that were avail-able to the public. These studies had been conducted in cars, buses, vans, trains, and aircraft. No data were found in the literature for heavy trucks. The experimental designs, methodologies, and instruments are summarized in Table 1.

IAQ Parameters Monitored

The studies of air quality in aircraft were more comprehensive than those in motor vehicles. The IAQ parameters measured in cars included temperature, relative humidity, particulate matter, CO, black carbon, nitrogen monoxide (NO), N[O.sub.2], ozone ([O.sub.3]), and volatile organic compounds (VOCs) (Limasset et al. 1993; Chan and Chung 2002; Rodes et al. 1998; Sato 2002). Some studies compared the ratio of the concentrations of the indoor contaminants to outdoor air contaminants. Compared to vehicles, more air quality parameters in aircraft were available. The IAQ parameters measured in aircraft included temperature (T), RH, pressure, particulate matter (P[M.sub.2.5], P[M.sub.10], particle count), CO, C[O.sub.2], [O.sub.3], black carbon, chemicals (e.g., lead) on dust, PAH, N[O.sub.2], NO, and VOCs. In addition, nicotine, dust mites, allergens, sulfur dioxide (S[O.sub.2]), and microbiological organisms (bacteria, fungi, endotoxins, etc.) were also measured (Dechow et al. 1997; Pierce et al. 1999; Lee et al. 2000; BRE 2003; Nagda et al. 1992; Eatough et al. 1992).

Only a few studies that provided field data of IAQ in train cabins and/or methods for controlling the air quality through ventilation in trains were found in the literature search (Aizle-wood et al. 2005; Li et al. 2005; Chow 2002; Chow and Yu 2000; Dumyahn et al. 2000). In one of the few studies with field data, Li et al. (2005) reported several in-train air quality parameters including temperature, relative humidity, CO, C[O.sub.2], TVOC, TSP, P[M.sub.10], P[M.sub.2.5], P[M.sub.1], benzene, toluene, and xylene. Chow (2002) suggested that the ventilation rate in trains be kept at 25.2 [m.sup.3]/h per person in order to prevent the C[O.sub.2] level from exceeding 1000 ppm. Aizlewood et al. (2005) did a survey of 574 subjects between 16 and 69 years old and found that the passenger satisfaction scores (1 = clearly acceptable to 10 = clearly unacceptable) for both temperature and air quality were between 3.5 and 7.74 at 24[degrees]C to 33[degrees]C with different airflow conditions. Dumyahn et al. (2000) conducted two surveys, monitoring and comparing the air quality in aircraft, trains, buses, and subways. They found that the levels of C[O.sub.2] had a close relationship with passenger loads for all of the types of vehicles studied. Also, the levels of most VOCs in ground transportation were higher than in aircraft, except acetone and ethyl alcohol.

Instrumentations and Measurement Methods

Overall, there was no consistency in the instruments used for the field measurement of indoor air quality in transportation cabins. Different studies selected different instruments to monitor the pollutant components at different locations even for the identical IAQ parameters. This has resulted in a challenging task when comparing the data provided by different studies. For example, temperatures and relative humidity values were measured using various sensors. These sensors included HOBO sensors, platinum resistance temperature detectors (RTD), thin-film dielectric sensors, T-type thermo-couples, Vaisala humidity and temperature probe HMP44, electronic thermohydrograph, and thermistor sensors.

The gravimetrical method was often selected for measuring the mass concentrations P[M.sub.2.5] and/or P[M.sub.10]. Particle counts were measured using the light-scatting method and nephelometry methods for continuous respirable suspended particle (RSP) concentrations. However, no aerodynamic particle sizers were employed in all of the studies summarized herein. For particle counters, all of the instruments had very limited channels, probably as compensation for portability. PM counters were chosen in some projects to support time-based analyses that investigated the periods in which high levels of PM (ranging from 0.3 [micro]m) existed. It is difficult to compare these count concentrations with the existing standards or guidelines, which are provided in mass concentration. However, count concentrations are more valuable in estimating the fraction of fine particles that are the most threatening to the health of the occupant. Another important purpose of taking the count concentration is that it provides real-time data, allowing the analyzer to monitor the concentration changes, which vary depending on the time of the day.

The gas sensors for CO, C[O.sub.2], VOCs, N[O.sub.2], and [O.sub.3] seemed to be relatively more consistent. An electrochemical detector for CO and infrared sensors for C[O.sub.2] were chosen by most researchers. Almost all researchers chose the NIOSH Method 1500 and 1400 to quantify the levels of VOCs (Rodes et al. 1998; Limasset et al. 1993; Riediker et al. 2003; Pierce et al. 1999; Dechow et al. 1997; BRE 2004). For N[O.sub.2], most of the researchers chose the diffusion sampling methods; however, BRE (2003) chose electrochemical sensors, and Eatough et al. (1992) utilized their own BASS. Passive sample badges and MBTH-coated filters were commonly used for detecting [O.sub.3]. Both of these methods are based on the passive diffusion mode.

For in-vehicle air quality studies, both the inside and outside air quality parameters were monitored by some researchers. This approach is preferable for the assessment and identification of the association between indoor and outdoor air qualities. Due to the practical difficulties, no air quality parameters outside an aircraft have been reported. Occasionally, visual evaluations of occupant behaviors were also conducted. There are two methods that are widely used for this application. One method involves importing data from video cameras that record occupants' performance and behavior, while the other method, called volumetric particle tracking velocimetry (VPTV), collects more information in addition to the spatial distribution of the airborne contaminants.

Measured Indoor Air Quality in Cabins

The results of the field measurements in motor vehicles and aircraft are listed in Tables 2 and 3, respectively. Overall, very limited data have been reported for IAQ in motor vehicle cabins. Riediker et al. (2003) reported that the temperatures and RH values inside most cars were within the range of 20.3[degrees]C to 30.4[degrees]C and 25.7% to 46%, respectively. For motor vehicles, N[O.sub.2] concentration was in the range of 0.08 to 0.23 ppm, NO was in the range of 0.24 to 0.5 ppm, CO was below 6 ppm, and P[M.sub.2.5] and P[M.sub.10] were about 6 to 107 ug/[m.sup.3] and 14 to 105 ug/[m.sup.3], respectively. All the measured data were below the recommended values in the standards or guidelines (Environment Canada 1976; ASHRAE 1989, 2001; EPA 1991; ACGIH 2005).

There have also been a few evaluations of the association between the indoor and outdoor (I/O) air quality in the vehicles. The effect of the outside air on the inside air quality was found to be significant. In the study conducted by Chan and Chung (2002), the I/O ratios were 1.683 and 2.628 when a van was traveling through a tunnel and in a clean area, respectively. The I/O ratio of CO was 1.039. For VOCs, the temperature and RH had a significant effect on the diffusions of VOCs (Sato 2002). Moreover, fine particle concentrations and [O.sub.3] were found to be lower inside than outside of the vehicle. Riediker et al. (2003) showed that the concentrations of P[M.sub.2.5] and ozone by the roadside were 29.9 [micro]g/[m.sup.3] and 22.8 ppb, respectively, while the corresponding values in the car were 23.0 [micro]g/[m.sup.3] and 11.7 ppb, respectively. These results imply that when the air outside the vehicle was polluted, taking it into the vehicle will tend to pollute the air inside the vehicle. Automotive occupants have more control over the control strategies of the HVAC system than those in aircraft. An automotive driver can do this by using mechanical ventilation or natural ventilation or both; this can also affect the IAQ in ground transportation. When the air quality is worse outside, such as traveling on urban streets, opening windows would be a bad choice.

Almost all studies reached an agreement that the concentrations of the pollutants were higher on heavy traffic roadways. Rodes et al. (1998) found that the concentrations of all pollutants in Sacramento were 1.5 to 6 times more than those in Los Angeles. In addition, the levels of the pollutants also depend on the ventilation mode. The study by Chan and Chung (2002) is a good example. The mean values of the NO ratio while driving on the highway under the same road conditions were 0.574, 0.536, and 1.242 for recirculation, outside air intake, and opened windows modes of circulation, respectively. Also, using the same ventilation system mode of recirculation, the mean values of the NO ratio were 0.574, 2.680, 0.702, and 1.683 for highways, countryside, urban roads, and tunnels, respectively.

Data on air quality in railway transit are also included in Table 2. The mean values of most of the monitored air pollutants were well below the standards except for C[O.sub.2] (an average of 1177.4 ppm). However, the results from a questionnaire survey suggested that most passengers did not realize that the air quality had already passed 1000 ppm. Other major findings from this study were that the air quality had a significant seasonal variation and was strongly dependent on the time of day.

Comparison between the mean values in motor vehicles with those in airplanes showed that the air quality in motor vehicles was generally worse than that in airplanes, with only a few exceptions, such as RH. Most aircraft cabins are completely mechanically ventilated and high-efficiency filters are used to clean the recirculated air, whereas motor vehicles can be naturally ventilated. Motor vehicle drivers and passengers have more control over the in-cabin air quality via natural ventilation (lowering the windows), the outside air intake mode of ventilation, and/or the recirculation mode of ventilation.

In general, most of the mean pollutant levels were found to be below the threshold values in aircraft cabins. CO was less than 7 ppm, N[O.sub.2] varied from 3.9 to 70 ppb, and RSP was in the range of 1 to 17 [micro]m/[m.sup.3] for nonsmoking aircraft. All the highest values were found during noncruising periods and/or in smoking environments; the concentrations of the airborne contaminants (e.g., CO, C[O.sub.2], PM, VOCs, bacteria, and fungi) were higher than those at other time periods and locations. These conditions are mainly due to human activities, such as walking and the presence of clothing. Smoking was found to be the major factor that led to higher PM and nicotine levels (Nagda et al. 1992; Dechow et al. 1997; Eatough et al. 1992). Dechow et al. (1997) suggested isolating the nonsmoking locations from the smoking zones.

The C[O.sub.2] concentrations in aircraft were over 1000 ppm during the noncruising period, with a mean level of 1656/1232 ppm for the noncruising period at different locations and 1613/1405 ppm for domestic and international routes, respectively. Most passengers in air cabins felt comfortable (Lee et al. 1999); however, the perception of comfort was not very high because the actual temperatures and relative humidity levels in the airplanes were often out of the comfort range. The temperature varied between 16.7[degrees]C and 29.8[degrees]C and the RH varied between 4.9% and 76.8%.

Again, the difference in the instrumentation could have resulted in differences in accuracy and resolution, which made it more challenging to compare the data obtained in one study with those reported in another. It would therefore be better to compare the readings to the standard for the same IAQ parameters; however, no comparison between the field data and the relevant standards was conducted in most of the studies.

The information of placement of the sensor on the vehicles is also missing. It will also affect the measurement accuracy as well as the comparison. Ventilation effectiveness (Zhang et al. 2001) and the resulted spatial distribution of the air pollutants (Wang et al. 2000) were seldom considered in the existing literature. Although some studies employed multiple sensors at different sampling locations, there were few discussions on the optimum location where a representative sample can be taken. A systematic study by experiments and computational modeling to determine the optimum location would be valuable to IAQ monitoring in field.

It is worth mentioning that in the literature cited herein, there was limited information about body leakage characteristics for automotive applications. The influence of the body leakage characteristics has a major influence of infiltration or exfiltration into the cabin depending on the pressure profile over the body including under the body. And this issue will also dictate the concentration levels of the gases inside of the cabin.

SUMMARY AND CONCLUSIONS

This paper first introduced the health effects of IAQ in transportation cabins, followed by a comprehensive overview of the methodologies, instruments used, and major findings in recent studies of IAQ in transportation cabins. Overall, the field data for in-cabin, especially in-vehicle, air quality are very limited. The studies of air quality in aircraft not only started earlier but were also more comprehensive than studies in other transportation modes. A few studies of in-cabin air quality in cars, buses, vans, trains, and aircraft were found.

There is no standard regarding the instrumentation for in-cabin air quality monitoring. In the field studies that are reviewed, various instruments were employed even for detecting identical IAQ parameters. The difference in the instrumentation could have resulted in the differences in accuracy and resolution, which make it more challenging to compare one set of data with another. It would be better to compare he measurements to the acceptable standards or thresholds for the same IAQ parameters. In most studies, however, there was no comparison of the monitored results to the standards. In comparing the parameters estimated for motor vehicles to those obtained for airplanes, some of the air contaminates in vehicles were better than in airplanes, but others were not.

In general, most of the pollutant levels were found to be below the threshold values or guidelines in the aircraft cabins. Most passengers in air cabins felt comfortable in the cabin and considered the air quality to be excellent; however, the actual temperatures and relative humidity values were often in the uncomfortable range in airplanes, and the C[O.sub.2] concentrations in aircraft were over 700 ppm higher than the ambient C[O.sub.2] levels during the noncruising period. The major sources of these airborne contaminants, especially C[O.sub.2], in an airplane are its occupants.

Almost all studies reached the conclusion that the concentrations of the pollutants in motor vehicles were high under heavy traffic conditions. The levels of the pollutants were found to depend on the different ventilation modes used and the traveling conditions.

Few studies mentioned control strategies to improve air quality in cabins. Even if the air quality did not pose adverse effects on occupants due to short-term and noncritical exposure, the contaminant source control, air-cleaning technique, and ventilation rate increase need to be considered in order to maintain better air quality.

Some information, such as the ventilation effectiveness on the spatial distribution of the indoor air pollutants, is missing. In addition, no field measurement data for some transportation modes, including commercial trucks, were found in public literature. The IAQ in truck cabins will be collected and reported in Part II of this paper, which will expand the database of the IAQ in transportation.

ACKNOWLEDGMENTS

Support from the Centre for Transportation Engineering and Planning, Economy Carrier Limited, and the Alberta Motor Association is gratefully acknowledged. However, the views expressed by the authors do not necessarily reflect those of the organizations.

REFERENCES

Aizlewood, C., D. Butler, H. Emms, and L. Hamilton. 2005. Experimental evaluation of thermal comfort on underground trains. Proceeding of Indoor Air 2005: Program of the 10th international conference on Indoor Air Quality and Climate. pp. 123-27.

Akers, T.G., S. Bond, and L. J. Goldberg. 1966. Effect of temperature and relative humidity on survival of air-borne Columbia SK group viruses. Appl Microbiol. 14(3):361-64.

Alberts, W.M. 1994. Indoor air pollution: NO, N[O.sub.2], CO, C[O.sub.2]. J All Clin Immunol. 94:289-95.

ASHRAE. 1992. 1992 ASHRAE Handbook--HVAC Systems and Equipment. Chapter 25. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

ASHRAE. 2001. ANSI/ASHRAE Standard 62-2001, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

Baek, S.O. 1997. Indoor air quality in homes, offices and restaurants in Korean urban areas--Indoor/outdoor relationships. Atmospheric Environment 31(4):529-44.

Berglund, L.G. 1998. Comfort and humidity. ASHRAE Journal 40(8):35-41.

BRE. 2003. Client report number 212034. Extending cabin air measurements to include older aircraft--For the UK AHWG.

Chan, A.T., and M.W. Chung. 2002. Indoor-outdoor air quality relationships in vehicle: Effect of driving environment and ventilation modes. Atmospheric Environment 37:3795-808.

Chow, W.K. 2002. Ventilation of enclosed train compartments in Hong Kong. Applied Energy 71(3):161-70.

Chow, W.K., and C.H. Yu. 2000. Simulation on energy use for mechanical ventilation and air-conditioning (MVAC) systems in train compartments. Energy 25:1-13.

Coultas, D.B., and W.E. Lambet. 1991. Carbon monoxide. In: Sanet, J.M., Spengler, J.D., eds. Indoor Air Pollution: A Health Perspective. Baltimore, MD: Johns Hopkins University Press. pp. 187-208.

Dahms, T.E., L.T. Younis, R.D. Wiens, S. Zarnegar, S.L. Byers, and B.R. Chaitman. 1993. Effects of carbon monoxide exposure in patients with documented cardiac arrhythmias. Journal of the American College of Cardiology 21(2):442-50.

Dechow, M., H. Sohn, and J. Steinhanses. 1997. Concentrations of selected contaminants in cabin air of airbus aircraft. Chemosphere 35(1/2):21-31.

Dowing, C., and C. Bayer. 1993. Classroom indoor air quality vs. ventilation rate. ASHRAE Transactions 99:1099-103.

Dreher, K.L. 2004. Health and environmental impact of nanotechnology: Toxicological assessment of manufactured nanoparticles. Toxicological Sciences 77:3-5.

Dumyahn, T.S., J.D. Spengler, H.A. Burge, and M. Muilenburg. 2000. Comparison of the environments of transportation vehicles: Results of two surveys. In: Nagda, N.L., ed. Air Quality and Comfort in Airliner Cabins: ASTM STP 1393. West Conshohocken, PA: American Society for Testing and Materials. pp. 3-23.

EPA. 1991. Air Quality Criteria for Carbon Monoxide. Washington, DC: US Environmental Protection Agency.

Eatough, D.J., F.M. Caka, J. Crawford, S. Braithwaite, L.D. Hanse, and E.A. Lewis. 1992. Environmental tobacco smoke in commercial aircraft. Atmospheric Environment Vol 26A(12):2211-218.

Fang, L. 1998. Impact of temperature and humidity on perception of indoor air quality during immediate and longer whole-body exposures. Indoor Air 8:276-84.

Frampton, M.W., P.E. Morrow, C. Cox, F.R. Gibb, D.M. Speers, and M.J. Utell. 1991. Effects of nitrogen dioxide exposure on pulmonary function and airway reactivity n normal humans. American Review of Respiratory Disorders 143(3):522-27.

Galatsis, K.W. Wlodarski, Y. Li, and K. Kalantar-zade. 2000. Vehicle cabin air quality monitor using gas sensors for improved safety. IEEE Proceedings of the 2000 Conference on Optoelectronic and Microelectronic Materials and Devices. pp. 65-68.

Garvey, D.J., and L.D. Longo. 1978. Chronic low level maternal carbon monoxide exposure and fetal growth and development. Biology of Reproduction. 19:8-14.

Hauschildt, P., L. Molhave, and S.K. Kjaergaard. 1996. A climate chamber study: Exposure of healthy persons and persons suffering from allergic rhinitis to office dust. Proceedings of 7th International Conference--Indoor Air Quality And Climate-Indoor Air 96, Nagoya, Japan, July 21-26 1:659-64.

Jones, A.P. 1997. The main causative factors of asthma, available information on population exposure to those factors, and current measures of control. In: Asthma in Europe. European Federation of Asthma and Allergy Associations, Holland. pp. 207-301.

Lee, S.C., C.S. Poon, X.D. Li, and F. Luk. 1999. Indoor air quality investigation on commercial aircraft. Indoor Air 9:180-87.

Lee, S.C., S. Lam, and F. Luk. 2000. Investigation of cabin air quality in commercial aircraft. Proceedings of Healthy Buildings 1:471.

Li, T.T., J.F. Liu, G.S. Zhang, Z.R. Liu, and Y.H. Bai. 2005. Air quality in passenger cars of the ground railway transit system in Beijing, China. Proceedings of Indoor Air 2005. pp. 718-22.

Limasset, J., D. Franfois, and G. Hubert. 1993. Assessment of bus drivers' exposure to the pollutants of urban traffic. The Science of the Total Environment 134:39-49.

Lindgren, T., and D. Norback. 2002. Cabin air quality: Indoor pollutants and climate during intercontinental flights with and without tobacco smoking. Indoor Air 12:263-72.

Marr, L.C., G.C. Morrison, W.W. Nazaroff, and R.A. Harle. 1998. Reducing the risk of accidental death due to vehicle-elated carbon monoxide poisoning. J. A & WMA 48:899-906.

Mbithi, J.N., V.S. Springthorpe, and S.A. Sattar. 1991. Effect of relative humidity and air temperature on survival of hepatitis A virus on environmental surfaces. Appl Environ Microbiol. 57(5):1394-99.

MDH. 2004. Carbon dioxide. Minnesota Department of Health Fact Sheet. IC# 141-1422:1-2.

Nagda, N.L., M.D. Koontz, A.G Konheim, and S.K. Hammond. 1992. Measurement of cabin air quality aboard commercial airliners. Atmospheric Environment 12:2203-10.

OSHA. 1995. Standards-29 CFR. Table Z-1, Limits of Air Contaminants-1910.1000 Table Z-1.

Pan, Z.W., L. Molhave, and S.K. Kjaergaard. 1999. Irritation symptoms in eyes and nose after house dust exposure in the climate chamber. Proceedings of the 8th International Conference Indoor Air Quality and Climate-Indoor Air 99, Edinburgh, Scotland 2:612-16.

Pierce, W.M., J.N. Janczewski, B. Rowthlisber, and M.G. Janczewski. 1999. Air quality on commercial aircraft. ASHRAE Journal 41(9):26-34.

Pilotto, L.S., R.M. Douglas, R.G. Attewell, S.R. Wilson. 1997. Respiratory effects associated with indoor nitrogen dioxide exposure in children. International Journal of Epidemiology 26(4):788-96.

Raub, J.A., M. Mathieu, N.B. Hampson, and S.R. Thom. 2000. Carbon monoxide poisoning--A public health perspective. Toxicology 145:1-14.

Reinikainen, L.M., and J. Jaakkola. 1992. The effect of air humidification on symptoms and perception of indoor air quality in office workers: A six-period cross over trail. Archives of Environmental Health 47(1):8-15.

Riediker, M., R. Williams, R. Devlin, T. Griggs, and P. Bromberg. 2003. Exposure to particulate matter, volatile organic compounds, and other air pollutants inside patrol cars. Environ. Sci. and Technol. 37:2084-93.

Rienstra, S., and P. Rietveld. 1996. Speed behavior of car drivers: A statistical analysis of acceptance of changes in speed policies in the Netherlands. Transpn Res.-D. 1(2)97-110.

Rodes, C., L. Sheldon, D. Whitaker, A. Clayton, K. Fitzgerald, and J. Flanagan. 1998. Measuring concentrations of selected air pollutants inside California vehicles, Final report (950339). Sacramento, CA: California Air Resources Board.

Salome, C.M., N.J. Brown, G.B. Marks, et al. 1996. Effect of nitrogen dioxide and other combustion products on asthmatic subjects in a home-like environment. European Respiratory Journal 9(5):910-18.

Samet, J., W. Lambert, and A. Cushing. 1992. A study of respiratory illnesses in infants and N[O.sub.2] exposure. Archives of Environmental Health 47(1):57-63.

Samet, L., and W. Cushing. 1997. A study of respiratory illnesses in infants and N[O.sub.2] exposure. Archives of Environmental Health 47(1):57-63.

Sato, S. 2002. Air quality in auto-cabin. R & D Review of Toyota CRDL 39(1).

Schwarzberg, M.N. 1993. Carbon dioxide level as migraine threshold factor: Hypothesis and possible solutions. Medical Hypotheses 41(1):35-36.

Shima, M., and M. Adachi. 2000. Effect of outdoor and indoor nitrogen dioxide on respiratory symptoms in schoolchildren. International Journal of Epidemiology. 29:862-70.

Simoni M., L. Carrozzi, S. Baldacci, et al. 2002. The Po river delta (North Italy) epidemiological study: Effect of pollutant exposure on acute respiratory symptoms and respiratory function in adults. Arch Environ Health 57:130-36.

Simonson, C.J., M. Salonvaara, and T. Ojanen. 2002. The effect of structures on indoor humidity comfort and perceived air quality. Indoor Air 12:243-51.

Spengler, J.D., and D.G. Wilson. 2003. Air quality in aircraft. Proc. Instn Mech. Engrs., Vol. 217, Part E: J. Process Mechanical Engineering.

Spengler, J.D. 1993. Nitrogen dioxide and respiratory illnesses in infants. American Review of Respiratory Disorders 148(5):1258-65.

Tan, Z., and Y. Zhang. 2003. An overview of particulate matters in indoor environments: Sources and effects. ASHRAE Transactions 109(2):89-100.

The Royal Society. 2003. Report of the Health and The Environment Workshop 8.

Toftum, J., and A.S. Jorgensen. 1998. Effect of humidity and temperature of inspired air on perceived comfort. Energy and Buildings 28:15-23.

Townsend, C.L., and R.L. Maynard. 2002. Effects on health of prolonged exposure to low concentrations of carbon monoxide. Occup Environ Med. 59:708-11.

Tunnicliffe, W.S., P.S. Burge, and J.G. Ayres 1994. Effect of domestic concentrations of nitrogen dioxide on airway responses to inhaled allergen in asthmatic patients. Lancet 344(8939-8940):1733-36.

Viegi, G., L. Carrozzi, P. Paoletti, M. Vellutini, et al. 1992. Effects of the home environment on respiratory symptoms of a general population sample in middle Italy. Archives of Environmental Health 47(1):64-70.

Wang, X., Y. Zhang, L.Y. Zhao, and G.L. Riskowski. 2000. Effect of ventilation rate on dust spatial distribution in a mechanically ventilated airspace. Transactions of Amer. Soc. Agr. Engr. 43(6):1877-84.

Wyon, D.P., S. Lasson, B. Forsgren, and I. Lundgren. 1989. Standard procedures for assessing vehicle climate with a thermal manikin. Society of Automotive Engineers Technical Paper Series 890049, pp. 46-56.

Zhang, Y., X. Wang, G.L. Riskowski, and L.L. Christianson. 2001. Quantifying ventilation effectiveness for air quality control. ASAE Transactions 44(2):385-90.

Xiaoying Cheng

student Member ASHRAE

Zhongchao Tan, PhD

Associate Member ASHRAE

Richard Tay, PhD

Wenquao Yuan, PhD

Xiaoying Cheng is a graduate student and Zhongchao Tan is an assistant professor in the Department of Mechanical and Manufacturing Engineering, University of Calgary, Alberta, Canada. Richard Tay is a professor and the industrial chair of road safety in the Department of Civil Engineering, University of Calgary. Wenqiao Yuan is a research engineer at the International Truck and Engine Co., Melrose Park, Illinois.

Table 1. Methodologies of Recent Studies

Literature     Transportation

Rodes et al.   29 cars of 4 different types
(1998)         Indoor: Inside the cars
               Outdoor: Along the roadways and outside of the vehicles
               Nearest ambient air monitoring station
               No consideration of ventilation system
               September to October 1997
Chan and       Inside/outside of a van
Chung          4 cases: highway, countryside, tunnel, and urban street
(2002)         3 ventilation modes: A/C with recirculation, A/C with
                 outside air intake, and natural ventilation
               80 commuting trips from October 2001 to February 2002
Sato           Inside a car
(2002)         Closed doors and windows
               Ventilation mode: Recirculation
Riediker       10 nonsmoking patrol cars on a highway
et al.         Sampling point: Backside of the front passenger seat
(2003)         August to October 2001
Limasset       18 bus routes in Paris and 25 routes in Bordeaux
et al. (1993)  Indoor: Ventilation air intake
               Outdoor: Vehicle roof
Dumyahn        The spring of 1994 on aircraft over 22 domestic routes
et al. (2000)  1996 on 27 travel segments on aircraft, interstate
                 trains, interstate buses, short-distance commuter
                 trains, and subways
Limasset       18 bus routes in Paris and 25 routes in Bordeaux
et al. (1993)  Indoor: Ventilation air intake
               Outdoor: Vehicle roof
Li et al.      Ground railway transit
(2005)         July and August (summer) and December (winter), 2004
Pierce et al.  12 air flights
(1999)         Ventilation mode: 50% filtered recirculation, and
                 outside-air intake mode
               July 9 and 22, 1998
Dechow et al.  4 flight phases: 25 minutes before and after takeoff,
(1997)           before and after landing and cruising condition.
               Sampling points: 2 in the first/business class, 2 in
                 the economy class nonsmoking, and 2 in the economy
                 class smoking, 1 for outside and 1 for recirculated air
Nagda et al.   92 flights: 23 nonsmoking and 69 smoking
(1992)         April to June 1989
               4 sampling locations: smoking flights coach smoking
                 section, boundary region of the nonsmoking section
                 within three nonsmoking rows near the coach smoking
                 section, middle of the nonsmoking section, and remot
                 e nonsmoking section.
Lindgren and   26 flights with two aircraft types
Norback        3 years (November 1995 to November 1998)
(2002)         Fixed positions: in the aft on the wall (160 cm above the
                 floor) and forward galley on the working desk
BRE (2003)     14 flights with two types of airplanes
               Instruments in a flight case
               Different locations in cabin
               4 phases (each sample taking one minute): before
                 boarding, during passenger boarding, cruise, during
                 passenger disembarkation
               Winter 2002/2003
Lee et al.     16 flights
(2000)         June 1996 to August 1997
Eatough et     4 DC-10 flights
al. (1992)     Breathing height, fastened to the seat in front of the
                 volunteer
               The rear passenger cabin in economy class smoking section
                 at the rear of the aircraft
               Data collected by Briefcase Automated Sampling System
                 (BASS) with two dual vacuum pumps

Literature     IAQ                      Instrumentation

Rodes et al.   P[M.sub.2.5]             MSP personal impactors on
(1998)                                    polytetrafluorethylene
                                          (PTFT) filters by XRF,
                                          two-hour integrated samples
               P[M.sub.10]              MSP personal impactors on PTFT
                                          filters by XRF, two-hour
                                          integrated samples
               PM count                 LAS-X optional particle counter
               Black C                  Aethalometer real-time sample
               CO                       CO: Draeger monitors, continuous
                                          monitoring
               13 VOCs                  VOCs except formaldehyde: SUMMA
                                          by GC/MS; Formaldehyde: DNPH
                                          cartridges by HPLC
Chan and       N[O.sub.x]               Monitor Labs 9841 N[O.sub.x]
Chung                                     Chemiluminscent Analyzer
(2002)         CO                       Portable IAQCALC
Sato           13 VOCs                  EPA Toxic Organic Method
(2002)
Riediker       T and RH                 HOBO sensors
et al.         P[M.sub.2.5] mass        Personal environmental monitor
               P[M.sub.2.5] mass        Nephelometers
                 real-time                (personalDataRam, MIE,
                                          Bedford, MA).
               CO                       Portable Langan T15 CO gas
                                          monitor, an electrochemical
                                          sensor
               PAH on PM                Photoionization detector
               Elemental composition    Integrative samplers:
               of P[M.sub.2.5]            P[M.sub.2.5] mass, elemental
                                          carbon, elemental composition
                                          of P[M.sub.2.5], N[O.sub.2],
                                          ozone,  aldehydes, and VOCs
               [O.sub.3], N[O.sub.2]    Integrative samplers
               Aldehydes                Integrative samplers
               VOCs                     Integrative samplers
Limasset       CO                       Ecolyser (electrochemical
et al. (1993)                             detection) with a Mahiak Unor
                                          6N infrared nondispersive
                                          analyzer
               NOx                      AC 30 M Environment S.A.
                                          analyzer (chemiluminescent
                                          detection)
               Lead on dust             Cellulose acetate or quartz
                                          filters with atomic absorption
               Benzopyrene              Quartz filters with HPLC/UV
                                          fluorescence detector
               Formaldehyde             2, 4-DNPH silicagel tubes with
                                          HPLC/UV fluorescence detector
Dumyahn        T                        Summa canisters
et al. (2000)  RH
               CO
               C[O.sub.2]
               [O.sub.3]
               Surface dust and         Modified hand vacuums
                 biological compounds.
Limasset       Noise                    Did not mention the monitoring
et al. (1993)                             methodology
               VOCs                     Did not mention the monitoring
                                          methodology
               Surface dust, PM         Modified hand vacuums, analyzed
                                          for fungi, bacteria,
                                          endotoxin, cat, and dust mite
                                          allergens
Li et al.      T and RH                 Electric thermohydrograph
(2005)         CO and C[O.sub.2]        Portable sampler
               TVOC                     Phocheck 5000 portable TVOC
                                          monitor
               PM                       Dustmate fume and dust detection
               Benzene, toluene,        GC (Varian GC3800)
               xylene
Pierce et al.  T                        Sensors for temperature
(1999)         RH                       Sensors of relative humidity
               Pressure                 Sensors of pressure
               C[O.sub.2]               Sensors of C[O.sub.2]
               CO                       Sensors of CO
               [O.sub.3]                Sensors of [O.sub.3]
               [O.sub.2]                Sensors of [O.sub.2]
               PM                       Aerosol monitor for RSP with TWA
               TVOC                     NIOSH Method 1500 & 1400
               Ethanol                  -
               Formaldehde              EPA Method T011-A
               Acrolein                 -
Dechow et al.  PM (Count)               Particle counters (custommade
(1997)                                    model by DEHA) with eight
                                          sensors
               VOCs                     Gaschromatography/mass-
                                          spectrometry (GC/MS)
Nagda et al.   T                        Continuous, platinum RTD
(1992)         RH                       Continuous, thin-film dielectric
                                          sensor
               CO                       Solid polymer electrolyte
               C[O.sub.2]               C[O.sub.2] detector tube
               RSP                      Filtration with cyclone
                                          separator
                                        RSP (continuous): Nephelometry
               Nicotine                 Sodium-bisulfate treated filter
                                          with GC/nitrogen selective
                                          detector
               [O.sub.3]                MBTH-coated filter,
                                          spectrophotometer
Lindgren and   T                        SWEMA logger 15 for T-RH
Norback        RH                       SWEMA logger 15
(2002)         C[O.sub.2]               Rieken RI-411 A, an infrared
                                          spectrometer; and SWEMA
                                          logger 15 simultaneously with
                                          1-min average
               N[O.sub.2]               Diffusion sampler
               PM counter               Sibata P-5H2, a light-scattering
                                          detector
               [O.sub.3]                Diffusion sampler from IVL
                                          (Swedish Environmental
                                          Research Institute Ltd.)
               Formaldehyde             Glass fiber filters impregnated
                                          with  2,4-DNPH
                                          (dinitrophenylhydrazine) by
                                          liquid chromatography
BRE (2003)     T                        Temperature--T-type thermocouple
                                          and Dantec  54N50 low velocity
                                          analyzer
               RH                       RH--Vaisala humidity and
                                          temperature probe HMP44
               Pressure                 Wika pressure transmitter type
                                          S-10.
               Air speed                TSI air velocity transducer,
                                          8470.
               C[O.sub.2]               C[O.sub.2]--Anagas Multigas
                                          infrared
               CO and N[O.sub.2]        City Technology electrochemical
                                          sensor (A3CO EnviroCel)
               VOCs, (VVOCs)            GC-MS
               Carbonyl compounds       DNPH cartridge using
               (aldehydes and ketones)    acetonitrile and the eluant by
                                          HPLC with UV detection
               SVOCs                    Polyurethane (PU) foam plug by
                                          GC/MS/FID
               PM (count)               P-TRAK Ultrafine Particle
                                          Counter (8525)
               Surface dusts            Pre-weighed nylon bag filters by
                                          five point  mass balance.
               Dust mite and cat        Cat and house dust mite antigen
               allergens                  (Fel d1 & Der p1)--agitating
                                          samples in phosphate buffered
                                          saline at 4[degrees]C
                                          overnight
               Bacteria                 MB2 Microbiological Aerosol
                                          Samplers
               Fungi                    MB2 Microbiological Aerosol
                                          Samplers
               Endotoxins               Pyrochrome Limulus Amebocyte
                                          Lysate assay
Lee et al.     T                        Thermistor technique
(2000)         RH                       Thin-film capacitive technique
               CO                       Electro-chemical technique
               C[O.sub.2]               Nondispersive infrared
               Micro-organisms          Burkard air sampler with agar
                                          plates
               S[O.sub.2]               Airbag/pulse fluorescence
                                          S[O.sub.2] analyzer
               N[O.sub.2]               Airbag/chemiluminescence NOx
                                          analyzer
               [O.sub.3]                Passive ozone badges or Bio-
                                          check enzyme
               RSP                      Light-scattering detector
               Total hydrocarbon        Flame ionization detector by
                                          Total Hydrocarbon Analyze
Eatough et     T, P, and RH             Omega Model HX91 and 14LPC18A
(1992)         Nicotine                 2 mini-annular denuder followed
                                          by 1m PTFT filter (Zeflour,
               3-ethenylpyridine          Gelman Sciences) at 2 sLpm and
                                          analyzed by ion chromatograghy
                                          for nicotine and 3-
                                          ethenylpyridine and
                                          spectrophotometer for UV-PM
               UV-PM
               CO                       Integrated sampling: Sorbent
                                          tubes (Drager) at 0.2 sLpm
                                          while for [O.sub.3] at 0.5
                                          sLpm
               C[O.sub.2]               Continuous sampling at 0.03
                                          sLpm: CO: electrochemical
                                          technique (Neutronics, OTOX
                                          sensor);
               N[O.sub.x]               [O.sub.2]: combination electrode
                                          (Microelectrodes Inc., MI-270)
               N[O.sub.2]
               [O.sub.3]
               P[M.sub.2.5]             3 m PTFT membrane filter (Gelman
                                          Sciences) for gravimetric
                                          determination of concentration
                                          at 8 sLpm

Table 2. Measured Data in Cars

                                             Chan and Chuang
IAQ Parameters          Rodes et al. (1998)  (2002)

Temperature             -                    -
  ([degrees]C)
RH (%)                  -                    -
P[M.sub.2.5]              6-107              -
  ([micro]g/[m.sup.3])
P[M.sub.10]              14-105              -
  ([micro]g/[m.sup.3])
Black C                 <40                  -
  ([micro]g/[m.sup.3])
Total particles          10-4600 (#/cc)      -
N[O.sub.2] (ppb)        -                    80-230
NO (ppm)                -                     0.24-0.5
CO (ppm)                 <6                   0.9-1.4
C[O.sub.2] (ppm)
[O.sub.3](ppb)          -                    -
Aldehydes               -                    -
  ([micro]g/[m.sup.3])
C4-C11                  -                    -
  n-alkanes (ppb)
Toluene (ppb)           -                    -
Xylenes (ppb)           -                    -
Ethyl benzene (ppb)     -                    -
p-ethyl                 -                    -
  benzene (ppb)
Trimethyl               -                    -
  benzenes (ppb)
MTBE                      2-90               -
  ([micro]g/[m.sup.3])
Benzene                   4-54               -
  ([micro]g/[m.sup.3])
Formaldehyde            <22                  -
  ([micro]g/[m.sup.3])

                                                          Riediker et
IAQ Parameters          Li et al. (2005)                  al. (2003)

Temperature               8.8-31.2                        20.3-30.4
  ([degrees]C)
RH (%)                   36-87                            25.7-46
P[M.sub.2.5]             13.1-111.3                        4.4-58.7
  ([micro]g/[m.sup.3])
P[M.sub.10]              35.3-373.1                        -
  ([micro]g/[m.sup.3])
Black C                                                    1.1-5.0
  ([micro]g/[m.sup.3])
Total particles          57.2-538.5 ([micro]g/[m.sup.3])   -
N[O.sub.2] (ppb)          -                                1.6-212.1
NO (ppm)                  -                                -
CO (ppm)                  0.1-2.3                          0.7-5.9
C[O.sub.2] (ppm)        560-2700
[O.sub.3](ppb)            -                                4.6-69.9
Aldehydes                 -                                0-89.7
  ([micro]g/[m.sup.3])
C4-C11                    -                                5.1-335.8
  n-alkanes (ppb)
Toluene (ppb)             6.1-24 ([micro]g/[m.sup.3])      2.3-130.8
Xylenes (ppb)             1.2-10 ([micro]g/[m.sup.3])      1.4-12.1
Ethyl benzene (ppb)       -                                0.3-2.6
p-ethyl                   -                                0.1-1.1
  benzene (ppb)
Trimethyl                 -                                0.7-4.1
  benzenes (ppb)
MTBE                      -                                -
  ([micro]g/[m.sup.3])
Benzene                   6.4-31.2                         0.4-13.5
  ([micro]g/[m.sup.3])                                       (ppb)
Formaldehyde              -                                -
  ([micro]g/[m.sup.3])

Table 3. Measured Results in Aircraft

IAQ                                           Lee et al.  Pierce et
Parameters              BRE (2003)            (1999)      al. (1999)

Temp. ([degrees]C)      16.7-27.7             17.8-29.8   17.8-26.1
RH (%)                  7.4-54.2              4.9-76.8    8.8-27.8
C[O.sub.2] (ppm)        746-2219              423-4752    942-1959
CO (ppm)                <0.1-1.3              1-6         <0.1-7
PM ([micro]g/           428-75369             1-17/71-    <10
  [m.sup.3])            (#/c[m.sup.3])        264 (s)
NO (ppb)                -                     0.3-37.7    -
N[O.sub.2] (ppb)        20-70                 3.9-13.8    -
[O.sub.3] (ppb)         -                     0-90        -
S[O.sub.2] (ppb)        -                     1-2         -
TVOC (ppm)              11-1140               -           0.11-0.43
                        ([micro]g/[m.sup.3])
THC (ppm)               -                     1.8- 2.6    -
Formaldehyde            -                     -           <0.5-4.9
(ppb)
Acrolein (ppb)          -                     -           <1.5
Nicotine (ppb)          -                     -           -
Ethanol (ppb)           -                     -           -
Acetone (ppb)           -                     -           -
Fungi                   0-1360                17-107      <1-37
(CFU/[m.sup.3])
Bacteria                30-1960               44-93       39-244
(CFU/[m.sup.3])
Toluene (ppb)           -                     -           -

                        Dechow
IAQ                     et al.   Lindgren and
Parameters              (1997)   Norback (2002)

Temp. ([degrees]C)      -        17.4-26.8
RH (%)                  -        1-27
C[O.sub.2] (ppm)        -        709 (96% duration)
CO (ppm)                -        -
PM ([micro]g/           -        49/3 (smoking/non-
  [m.sup.3])                       smoking)
NO (ppb)                -        -
N[O.sub.2] (ppb)        -        14.1 ([micro]g/[m.sup.3])
[O.sub.3] (ppb)         -        19.2 ([micro]g/[m.sup.3])
S[O.sub.2] (ppb)        -        -
TVOC (ppm)              -        -
THC (ppm)               -        -
Formaldehyde            3-26     <5
(ppb)
Acrolein (ppb)          -        -
Nicotine (ppb)          0.2-26   -
Ethanol (ppb)           149-     -
                        1790
Acetone (ppb)           3-236    -
Fungi                   -        -
(CFU/[m.sup.3])
Bacteria                20-1700  -
(CFU/[m.sup.3])
Toluene (ppb)           2-135    -

                        Eatough                          Nagda et al.
                        et al.                           (1992)
IAQ                     (1992)            Dumyahn et     (smoking/non-
Parameters              (smoking)         al. (2000)     smoking)

Temp. ([degrees]C)                        19-28          -
RH (%)                                    10-55          -
C[O.sub.2] (ppm)                          750-2000       1562-1568/1756
                                                           ([micro]l/l)
CO (ppm)                0.14-1.94         0.7            0.6-1.4/0.5-0.6
                                                           ([micro]l/l)
PM ([micro]g/[m.sup.3]  16-213            3-90           30.7-175.8/
                                                         34.8-40
NO (ppb)                                                 -
N[O.sub.2] (ppb)        0-4               >36            -
[O.sub.3] (ppb)                                          0.01/0.02
                                                         ([micro]l/l)
S[O.sub.2] (ppb)                                         -
TVOC (ppm)                                               -
THC (ppm)                                                -
Formaldehyde                                             -
(ppb)
Acrolein (ppb)                                           -
Nicotine (ppb)          0.1-471.6                        0.05-13.43 (s)/
                        (nmol/[m.sup.3])                 0-0.08
                                                         ([micro]g/
                                                         [m.sup.3])
Ethanol (ppb)                                            -
Acetone (ppb)                                            -
Fungi                                     44810-171790   50-59(s)/90
(CFU/[m.sup.3])                           (CFU/gm dust)
Bacteria                                  103-1210       131.2-162.7(s)/
(CFU/[m.sup.3])                                          131.1
Toluene (ppb)                                            -