Performance Evaluation For Indoor Passive Panels.
The advantage of using IPPT is that it is not associated with increased ventilation, which can increase energy consumption. In addition, there are no mechanical forces involved in the uptake of pollutants onto the IPPT surfaces. As an alternative to conventional active "flow through" pollutant removal systems relying on HVAC fans, IPPT can remove indoor pollutants relying on normal airflow characteristics in ventilated rooms (1) through contact on surfaces in occupied spaces. Thus, IPPT has the potential to improve indoor air quality with little or no impact on energy consumption, making it a potentially attractive IAQ solution.
IPPTs use primarily two processes to remove indoor pollutants, sorption and PCO. Sorptive-based IPPTs rely on physical adsorption and chemisorption processes. Solid adsorbents used in sorptive-based IPPT include activated charcoal and other materials such as silica gel, activated alumina, zeolites, porous clay minerals, and molecular sieves. PCO-based IPPTs rely on the use of photocatalysts on building materials, illuminated with either ultraviolet or visible light. In theory, the photocatalyst absorbs photons of ultraviolet or visible light to cause oxidation and reduction reactions on the catalyst's surface. Highly reactive species (e.g., hydroxyl radicals, ozone and superoxide ions) formed during these reactions have the potential to oxidize pollutants to mostly benign products such as carbon dioxide and water.
Despite the promising potential of IPPT, several issues may be associated with its use. First, some sorptive-based IPPTs may effectively adsorb certain gaseous indoor air pollutants (e.g., VOCs), but will not efficiently adsorb very volatile organic compounds (VVOCs) and low molecular weight gases such as formaldehyde. (2)
Second, certain sorptive-based IPPT may re-emit captured VOCs upon saturation and subsequently become a source of indoor pollution themselves. (3) Surface treatment (e.g., paint, primer and wallpaper) or particles contaminating IPPT surfaces may adversely affect pollutant-removal performance by hindering the contact between indoor pollutants and IPPT materials. (2) Traditionally, PCO technology relies on photocatalysts such as titanium dioxide (Ti[O.sub.2]), which require UV light Zuraimi Sultan is a research officer at the Construction Portfolio, National Research Council Canada, Ottawa, Ontario. for activation, making them appealing for outdoor applications. However, the band edges of the active photocatalyst lie in the UV region, which makes them inactive under visible light irradiation. (4)
Additionally, films on building windows are typically laminated with special layers modified with material that absorb, scatter, or reflect UV light. New catalytic technologies using modifications on the surface to reduce band gap or improve semiconductor coupling can use visible light to make indoor applications possible. However, it is unclear how effective these new technologies will be in removing indoor pollutants. (4) Last, PCO-based IPPT may not just produce active agents to attack indoor pollutants, but they may also produce harmful ozone and formaldehyde as by-products. (2,4)
Within the Government of Canada's Clean Air Regulatory Agenda (CARA), researchers from the National Research Council of Canada (NRC) have recognized a critical standardization gap, as sound evaluation protocols and test methods were limited to comprehensively and fairly validate IPPT manufacturers' claims.
While available standards address important aspects of indoor pollutant removal performance, (5-8) none deal with other specific performance issues for indoor applications such as: harmful by-product formation to protect human health; re-emission of captured VOC; and IPPT testing in chambers that can simulate air velocity and turbulence levels typically found in indoor environments, (9) as well as simulate visible light illumination using a conventional indoor lighting source (instead of a UV source).
NRC researchers focused on three priority areas to develop a protocol to assess IPPT performance, specifically:
1. Performance of sorptive and PCO-based IPPTs in removing formaldehyde and toluene;
2. Formation of by-products from the IPPT; and
3. Re-emission of captured VOC.
In December 2015, NRC researchers published a protocol titled "Indoor Passive Panel Technologies:
Test Methods to Evaluate Toluene and Formaldehyde Removal and Re-Emission, and By-Product Formation." (2) This protocol provides a method to determine the performance of IPPT in terms of their capacity to remove two important indoor air pollutants in Canadian indoor environments, formaldehyde and toluene.
Formaldehyde was chosen because it produces adverse health effects (classified as a carcinogen, eye and skin irritant, association with asthma and allergic-type symptoms), is emitted by many building materials and is found in indoor settings sometimes at concentrations that exceed Health Canada's guideline. (10) The VOC toluene was chosen to represent emissions from numerous indoor sources (e.g., from solvents and paints), as well as to reflect its relative abundance and prevalence in indoor air. (11) The protocol evaluates the potential formation of harmful by-products through determining emissions of ozone and formaldehyde. (10,12)
To be able to validate this protocol, NRC researchers developed a 400 L (106 gallon) stainless steel chamber with accurate control of environmental conditions (e.g., temperature, relative humidity, airflow, air velocity and turbulence) according to specifications described by Zhang, et al., (9) and a VOC injection system to introduce the VOCs. (13) In addition, fluorescent light is used, as opposed to UV, (7,8) as a source of illumination to better represent indoor applications (Photo 1).
Two commercial samples were successfully used to evaluate the protocol. The protocol was used to differentiate the formaldehyde removal performance of a conventional gypsum board with that of a sorptivebased IPPT gypsum board. Figures 1 and 2 illustrate the concentration versus time profile for the two test samples challenged with formaldehyde over 96 hours. It can be observed that between 48 and 96 hours the inlet-outlet concentration differences were an average of 15.7 [micro]g/[m.sup.3] and 59.3 [micro]g/[m.sup.3] for the conventional and IPPT samples, respectively. These values correspond to average area specific removal rates ([RR.sub.A]) of 35.2 [micro]g/hr*[m.sup.2] and 133.2 [micro]g/hr*[m.sup.2], indicating that the removal rate of the IPPT gypsum board was 3.8 times higher than the conventional board.
After the formaldehyde injection was stopped at 96 hours, we observed that the conventional gypsum board began to release formaldehyde up to 168 hours when the test was terminated. Re-emission of formaldehyde (Re) as measured at 168 hours, recommended by the protocol, was calculated to be 39.7% for the conventional gypsum board. In contrast, the sorptive-based IPPT gypsum board has an Re value of only 0.9%, indicating minimal re-emissions.
In summary, NRC researchers have developed a protocol to evaluate the performance of IPPT in their ability to remove formaldehyde and toluene and to determine re-emissions of captured pollutants and by-product formation. Through this novel protocol and NRC's new IPPT chamber testing capabilities, NRC is now in the position to test IPPT products to enable manufacturers to validate their claims, and even improve their product performance. The development of the protocol was conducted under the guidance of the Technical Advisory Committee. The committee members included participants from federal and provincial agencies, industry associations, non-governmental organizations, municipal governments, and standards associations from Canada.
(1.) Zhang, J.S., et al. 1995. "Field measurement of boundary-layer flows In ventilated rooms." ASHRAE Transactions 101(2):1-9.
(2.) Sultan, Z, R., et al. 2015. "Indoor Passive Panel Technologies: Test Methods to Evaluate Toluene and Formaldehyde Removal and Re-Emission, and By-Product Formation." National Research Council Canada.
(3.) Ataka, Y, et al. 2004. "Study of effect of adsorptive building material on formaldehyde concentrations: development of measuring methods and modeling of adsorption phenomena." Indoor Air 2004. 14(Suppl 8):51-64.
(4.) Ifang, S, et al. 2014. "Standardization methods for testing photo-catalytic air remediation materials: Problems and solution." Atmospheric Environment 91(7):154-161.
(5.) ISO. 2009. ISO 16000-23:2009, Performance Testfor Evaluating the Reduction of Formaldehyde Concentrations by Sorptive Building Materials. International Organization for Standardization.
(6.) ISO. 2009. ISO 16000-24:2009, Performance Testfor Evaluating the Reduction of Volatile Organic Compounds Concentrations (Except Formaldehydee) by Sorptive Building Materials. International Organization for Standardization.
(7.) ISO. 2011. ISO Standard 22197-3:2011, Fine Ceramics (Advanced Ceramics, Advanced Technical Ceramics)--Test Method for Air-Purification Performance of Semiconducting Photocatalytic Materials--Part 3: Removal Of Toluene. International Organization for Standardization.
(8.) ISO. 2013. ISO Standard 22197-4:2013, Fine Ceramics (Advanced Ceramics, Advanced Technical Ceramics)--Test Method for Air-Purification Performance of Semiconducting Photocatalytic Materials--Part 4: Removal of Formaldehyde. International Organization for Standardization.
(9.) Zhang, J.S., et al. 1996. "Study of air velocity and turbulence effects on organic compound emissions from building materials/ furnishings using a new small test chamber." ASTM Symposium on Methods for Characterizing Indoor Sources and Sinks. Page 184-199.
(10.) Health Canada. 2006. "Residential Indoor Air Quality Guideline--Formaldehyde."
(11.) Health Canada. 2011. "Residential Indoor Air Quality Guideline--Toluene."
(12.) Health Canada. 2010. "Residential Indoor Air Quality Guideline--Ozone."
(13.) Deore B., et al. 2011. 'An electronic nose for the detection of carbonyl species." ECS Transactions 35(7):83-88.
BY ZURAIMI SULTAN, PH.D., MEMBER ASHRAE
Caption: FIGURE 1 Testing of normal gypsum board against formaldehyde using the new protocol.
Caption: FIGURE 2 Testing of sorptive-based IPPT gypsum board against formaldehyde using the new protocol.
Caption: PHOTO 1 Chamber set-up to evaluate performance of IPPT samples using the new NRC protocol.
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|Title Annotation:||COLUMN IEQ APPLICATIONS|
|Date:||Jul 1, 2016|
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