Thermal burden of N95 filtering facepiece respirators

Increased thermal perceptions that affect comfort are a leading reason for intolerance to wearing respiratory protective equipment. Despite their popularity and use for decades, relatively little is known about the thermal burden imposed by the use of N95 filtering facepiece respirators (FFR) at normal work rates. Twenty healthy subjects exercised at a low-moderate work rate for 1 and 2 h while wearing four models of N95 FFR (two with an exhalation valve) as core and skin temperatures were monitored wirelessly. N95 FFR use resulted in non-significant minimal increases in core temperature and uncovered facial skin (cheek) temperatures. Facial skin temperature under the FFR was significantly increased over baseline values (P < 0.001). Wearing N95 FFR for up to 2 h at a low-moderate work rate does not impose a significant thermal burden on core temperature and uncovered facial skin temperature but significantly increases the temperature of the facial skin that is covered by the FFR. Perceptions of increased body heat when wearing N95 FFR under the test conditions are likely not due to effects on core temperature but may relate more to warming of the facial skin covered by the respirator and warming of the inspired air.