Guidelines on the Risk and Time to

The objective of the present study was to define the risk and the time required to develop frostnip on the face during exposure to cold winds. Twelve subjects (6 males and 6 females) were exposed to sixteen 45 min tests where the wind intensity varied between 0, 16 and 32 km/h. The tests were conducted at 0, -10, -20, -30, -40 and –50°C (only 0 km/h wind was present at -50°C). During the tests, the subjects were dressed for thermal comfort, and rested seated while facing the wind with their bare face fully exposed to the cold wind. Each test was terminated when the elapsed time reached 45 min, or when frostnip developed. The results show that no frostnip was observed at 0°C and -10°C for any wind intensity. The frequency of frostnip development increases inversely with temperature, while the time to develop frostnip increases with temperature. At -20°C, 17 and 58% of the subjects developed frostnip for the 16 and 32 km/h wind conditions, while at –30 and -40°C, all the subjects developed frostnip at those conditions. For the no wind conditions, 0, 11, 22, and 60% of the subjects developed frostnip for the –20, -30, -40 and -50°C conditions, respectively. The time to develop frostnip decreased from 20 min at -20°C for the 16 and 32 km/h wind conditions to 14, 4, 2.5 and 1.5 min for the -30°C and 16 km/h, -30°C and 32 km/h, -40°C and 16 km/h, and -40°C and 32 km/h condition, respectively. It was concluded from these results that the risk of frostbite and times to develop frostbite estimated from Siple and Passel are based on conditions that are too severe and need revision to include more mild conditions. A new guideline based on the new Wind Chill Index is proposed to protect the general population against the development of freezing injuries, particularly on the face.