The effect of evaporative cooling of respiratory protective devices on skin temperature, thermal sensation, and comfort.
Am Ind Hyg Assoc J 1993 Dec; 54(12):705-710
The effect of evaporative cooling of respirators on skin temperature, thermal sensation, and comfort was examined. Six male volunteers, 19 to 66 years old, were fitted with a sham aluminum respirator mask (Al mask) or a modified Scott model 66 twin cartridge respirator mask (Scott mask). The outer surfaces of the Al mask and the chin area of the Scott mask were covered with felt. Thermocouples were attached to the nasolabial folds of the subjects. The subjects wore both masks while resting and the Scott mask while performing cycle ergometer exercise at 60 watts for two 30 minute periods during which the felt was moistened or kept dry. Temperatures were also measured between the seal and chin surface and on the inner and outer surfaces of the Scott mask. The subjects were asked to rate the acceptability and perceived level of comfort and thermal sensation periodically during the tests. It was hypothesized that evaporation of water from the moist felt would make the masks more comfortable than when the felt was kept dry (no evaporative cooling). When the Al mask with the dry felt was worn, the temperature of the nasolabial fold increased rapidly for 10 minutes, more slowly for the remaining 20 minutes, eventually reaching 35.5 degrees-C. When the felt was wet, the skin temperature remained constant at 34.8 degrees. The subjects rated the mask with dry felt as slightly warm and the mask with wet felt as slightly cool to neutral. The cooled mask was rated as being significantly more comfortable. While wearing the Scott mask without evaporative cooling, the temperature of the nasolabial fold after rest and exercise averaged 34.7 and 33.8 degrees, respectively. With evaporative cooling, the temperatures averaged 34.0 and 32.5 degrees, respectively. Cooling significantly reduced the temperatures of the inner and outer surfaces. The subjects rated the Scott mask as being significantly more comfortable when it was evaporatively cooled during rest than when not cooled. Ratings of thermal sensation and comfort during exercise did not differ between the cooled and noncooled condition. The authors conclude that under resting, and possibly exercise, conditions the skin temperature under an uncomfortable mask can be lowered into the comfort zone by evaporative cooling.
NIOSH-Publication; NIOSH-Grant; Respirators; Respiratory-protective-equipment; Cooling-systems; Thermal-effects; Psychophysiology; Laboratory-testing; Industrial-hygiene; Comfort-zones; Temperature-measurement; Physical-exercise
None John B Pierce Foundation, Inc 290 Congress Avenue New Haven, Conn 06519
Respirator Research; Respirators
American Industrial Hygiene Association Journal
John B. Pierce Foundation Lab, Inc., New Haven, Connecticut