Background Respirators protecting against airborne particles and gases are also needed in cold environments. However, low temperature causes special problems such as freezing of exhaled moisture in the respirator, increases respiratory resistance and hampers communication. Fan-assisted respirators aim to solve the problem of respiratory resistance. However, there are a lot of complaints that the high and continuous air flow inside the face shield cools the face and eyes. This study aims to quantify the cooling problem and seeks solutions.
Methods Fan-assisted respirator with the face shield together with the battery-powered fan and filters was used. Air flow rates were 170 and 240 l/min. Exposure temperatures were −10, −20 and −30°C. Under the face shield the face skin was either unprotected or protected by a facemask (balaclava with a ventilator). Five male volunteers participated in the study. Face skin temperatures were measured at forehead, cheek, nose and lower lip. In the exposure temperature the subjects were standing, stepping and lifting for altogether 30 min.
Results Face skin temperatures were between 5 and 17 °C and thermal sensation was “cold” without the facemask. While the facemask was used skin temperatures were between 17 and 30 °C and thermal sensation was “slightly cool”. Fogging of the visor started from the sides in 10 to 15 min (exercise started) and humidity started to freeze soon after, regardless of the use of the facemask.
Conclusions The flow of air inside the fan-assisted respirator decreased skin temperatures to uncomfortable level within 5 −10 min without the facemask. The lowest temperature was measured in the lower lip. The use of facemask kept the skin temperatures in comfort/acceptable level. Freezing of exhaled moisture in the face shield was a marked problem without and with the facemask. It seriously restricted the eyesight causing a critical safety issue. Further development is needed for the respiratory protection in the cold.
- Fan-assisted respirator
- facial cooling