The Latest on Infrared Thermometers.

A Proposed Standard

Because of this column--and our early introduction of the infrared thermometer to the environmental health profession--we were asked to serve on the Underwriters Laboratories, Inc. [R] Technical Committee to develop the Standard for Infrared Thermometers (UL2333). The requirements set forth in this standard will cover portable, battery-operated infrared thermometers and their accessories, which are intended specifically for use in food safety. A proposed first edition of the standard was sent to the committee for balloting in February of this year; we are anxiously awaiting the ballot outcome and hope that this document will be recognized as a new American national standard.

The reason for our enthusiasm is not only that this proposed standard sets forth instrument safety and performance parameters--including appropriate labeling requirements. More important, the instructional manual provides a uniform and comprehensive guide on the use and care of the instrument. This information is essential if sanitarians are to use the infrared thermometer appropriately. We hope that once the standard is adopted, each instructional manual will include specific language intended to dispel any misinformation or misunderstanding about the capabilities and application of the instrument. To this end, the proposed standard recommends that the following precise language must be included in the instructional manual that accompanies each new instrument:

* Infrared thermometers only measure surface temperature. Therefore, in food applications, critical temperatures must be verified with an internal temperature-measuring device.

* Failure to precondition the instrument may result in thermal shock and/or inaccurate measurements.

* For the most accurate temperature measurements, aim the infrared thermometer perpendicular to the target.

* Avoid storing the unit in extreme temperature conditions. Do not store infrared thermometers at temperatures below freezing or where the radiant temperature may exceed 48.9[degrees]C (120[degrees]F).

* The lens should be free of dirt, dust, moisture, fog, smoke, and debris.

* If the unit has a laser-sighting device, the appropriate laser safety warnings will also be included.

Each instructional manual must include additional information as well:

* the proper application and operation of the unit, including specific methods for measuring temperature (each manual should instruct users on determining the distance at which they should hold the device from the surface being measured and how large a surface area the device measures at that distance);

* emissivity instructions that cite any limitations of use for the unit and provide information on the appropriate setting for devices with adjustable emissivity controls;

* specifications on response times needed for accurate readings;

* complete battery instructions, including battery life in hours of operation;

* instructions on protecting the device from damage on what to do if the unit suffers mechanical abuse or damage; and,

* instructions for conducting field verification of accuracy and a recommendation that such verification be performed on a regular basis (for those sanitarians who routinely use the infrared thermometer, our column in the October 1999 issue of the Journal suggests a simple and easy method for field verification).

Two New Portable Models with Unique Features

The last time the UL2333 Technical Committee met, the representatives from OMEGA Engineering, Inc., [*] offered us two handheld infrared thermometers to evaluate. Both thermometers start out from the same basic unit within the OS643 series, but that is where the similarity ends.

Before we give you the specifics on the units we took into the field, we should tell you about the family of OS643 Stick Type Infrared Pyrometers. To begin: The OS643 series comprises five models; they are quite similar to those devices we have evaluated in previous columns. These models are inexpensive-- starting at $85--and the design is compact. Each unit comes in a sturdy carrying case with a belt loop and has back-lit LCD analog display and resolution. Three of the five models within the OS643 series are ideal for food safety evaluations. The LS model has a 12-dot laser guide, the W model comes with thermocouple input, and the basic model is a stripped-down common denominator of both, These three models all have a fixed emissivity (E) of 0.95 and a temperature range of 32 to 500[degrees]F (0 to 260[degrees]C). The other two models in the OS643 series have an adjustable E and a wider temperature range; these features are better suited for mechanical applications.

The LS model is an absolute pleasure to work with. The 12-dot circular laser guide is a unique feature that takes the guesswork out of the distance-aspect ratio. The temperature of the area inside the laser circle pattern is exactly what the unit is measuring, and the pattern expands proportional to the distance from the target. We have found that we can comfortably take numerous temperature measurements by standing in one spot, provided the circle guide does not go outside the target area. The beauty of using this model is that it provides us with the ideal opportunity to educate our clients. We do not have to move about to take temperatures, and the red circular pattern is a spectacular visual aid. The OS643LS model is most useful in our institutional work, particularly for evaluating comfort levels associated with radiant temperature in correctional facilities and schools. The unit sells for $115--a worthwhile expenditure for the benefit of the laser guide.

The OS643W model is ideally suited for quality control in he kitchen and serving area. Although the unit has no laser guide, it really does not need one because it is designed to be used close to the target. What makes this model unique is that has thermocouple input. This feature lets you zap the outside and verify the internal temperature of food with the flick of a witch. We waited until we could use this unit in a large, multiple-feeding facility before we put it through its paces. We were pleasantly surprised with its performance and ease of use. With the pyrometer in one hand and the thermocouple probe in the other, we were able to measure both the internal and external temperatures of food on an entire serving line simply by flicking a switch. We were able to complete the task in a fraction of the time it usually takes with two separate units or a thermocouple alone. Another nice feature of this unit is that the W model accepts any K-type thermocouple. Omega supplied us with its KTSS-HH probe (one of many offered in it catalog), but we learned that we could use any probe with compatible connector. This means that the probes commonly used on most thermocouple thermometers are interchangeable. We also found that we could effectively use the OS643W pyrometer with numerous K-type air- and surface-temperature probes we had in our arsenal of accessories. The W model therefore provides us with a wide range of inspection possibilities and, although it is slightly more expensive ($135) than the LS model, its versatility makes it a worthwhile addition to any sanitarian's tool kit.

We urge you to visit the OMEGA Engineering, Inc., Web site at [less than]http://www.omega.com[greater than]. The technical references are excellent and easily accessible. Through their site, we were able to download an excellent article by John Merchant, sales manager at the Mikron Instrument Company, Inc., titled "Infrared Temperature Measurement Theory and Application." In nonmathematical terms, this article explains the theory on which the technology is based, and it describes how infrared temperature measurement serves in a wide variety of applications. We recommend this article as required reading for everyone using infrared technology in the field.

A Final Note

We are aware of the ongoing concerns about the use of infrared technology as a quality assurance tool in the food service industry. The argument is as follows: Infrared technology measures surface temperatures, whereas applicable codes require internal temperatures for accuracy, safety, and enforcement. Of particular concern is the scenario in which infrared technology is used exclusively to measure the external temperature of a potentially hazardous food without the benefit of a probe thermometer. It is altogether possible that the external temperature could meet code requirements while the internal temperature of a food undergoing cooling or being held in bulk quantities could be dangerously outside the safety limits. For this reason, we strongly recommend that every health agency, institution, and industry provide its personnel with comprehensive and, if possible, competency-based training before adding infrared technology--as an adjunct--to any inspection and quality control program. We also urge all user s to carry a copy of the infrared technology instruction manual into the field to help answer any questions and assuage any concerns regarding this technology.

(*.) Omega Engineering, Inc., P.O. Box 4047, Stamford, CT 06907-0047. Telephone: [phone]; fax: [phone].