Infrared Thermometry in the Measurement of Heat Stress in Firefighters Wearing Protective Clothing

Abstract

This study investigated the performance of a new infrared-sensing thermometer in the determination of heat stress in firefighters performing moderate exercise in two protective clothing ensembles. All existing consensus standards approach the topic of heat stress monitoring and prevention. These standards are designed to keep the core body temperature of workers below 38°C. Direct measurement of rectal temperature is inconvenient and impractical, so surrogate measures of environmental heat have been widely accepted. Surrogate measures are poor predictors of heat stress in situations where protective clothing interferes with the body's means of losing heat. In these situations, direct measurement of the body's response to heat is desirable. Previous investigation had shown the effectiveness of infrared thermometry in a surgical setting, but no research had been done in the area of worker monitoring.

Eight hazardous materials-trained firefighters exercised on a stair machine while wearing gym clothing, firefighters' protective clothing, and fully encapsulating chemical protective clothing. Temperature measurements from rectal and skin surface probes were compared to those from an infrared thermometer to determine whether the instrument would be an effective tool to monitor healthy, exercising subjects and to determine if wearing protective clothing contributes to heat stress. Changes in deep body and skin surface temperatures due to the clothing ensembles were examined while the subjects exercised.

Both firefighters' protective clothing and chemical protective clothing induced significant heat stress in the subjects (p < 0.001). Results of the infrared thermometer performance indicated that the instrument tracked well with the rectal probe during the exercise portion of the trials (r = 0.94). However, during the recovery portion of the trials, the readings from the instrument did not reflect measured rectal temperatures. Apparently, while the instrument worked well in a surgical setting, its use in field monitoring of workers may underestimate the heat stress of workers. Hower, T.C.; Blehm, K.D.: Infrared Thermometry in the Measurement of Heat Stress in Firefighters Wearing Protective Clothing.