Oral and tympanic temperatures as heat strain indicators for workers wearing chemical protective clothing

Oral (Tor) and tympanic (Tty) temperatures were examined as alternatives for rectal temperature (Tre) as a heat strain indicator. Subjects were 20 male volunteers (age = 18-33 yr). A workload was determined in chemical protective clothing (CPC) by having the subject walk on a treadmill until a VO2 uptake of 1.33 (L/minute (approximately 650 W) was reached. At a second session subjects donned CPC and walked on the treadmill at the previously determined workload until Tre reached 39 degrees C, or heart rate reached 185 bpm, or volitional fatigue, i.e., one work cycle. Subjects then rested for 48 minutes. This cycle continued for 4 hours or until absolute fatigue at < 4 hours. Heart rate, Tor, Tty, Tre, and mean skin temperature were recorded every 10 minutes and at the end of work. A paired t-test was used to determine if a significant difference in the magnitude of temperature increase in Tor and Tty as compared with Tre existed. No significant difference (p > 0.05) was observed in delta Tor against delta Tre at 20, 30, 40, and 60 minutes of exercise, but delta Tor failed to display nonsignificant mean differences consistently throughout the test. However, delta Tty displayed no significant mean differences (p > 0.05) against delta Tre throughout the test. Tty significantly correlated with Tre at the 30- and 50-minute intervals (p < or = 0.05) and the end reading (p < or = 0.01). A repeated measures analysis of variance showed no significant difference between Tty and Tre over time. It was concluded that Tty has potential as a heat strain indicator for workers wearing CPC in the field, but Tor does not.