Guidelines on the Risk and Time to Frostbite during Exposure to Cold Winds

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. 1.0 INTRODUCTION Past studies have examined the effect of the wind chill on the development of frostnip in the fingers [2; 8]. There is limited data available for the risk and time to frostnip for the skin on the face. Wilson [7] has suggested that different parts of the body (e.g., the finger and the head) will cool at different rates due to differences in diameter. In addition, the turbulence of air flow varies for objects of different shape [7]. Therefore, the risk and time to frostnip data that is available for the fingers will not necessarily apply to the face. Siple and Passel [6] provided facial frostnip data by recording the time and location of frostnip on various parts of the face. However, their research took place under only two environmental conditions that were quite severe (i.e., the first at -32.5°C, 7 m/s wind or an average cooling rate of 2000 kg cal/m/h, and the second for an average cooling rate of 2308 kg cal/m/h). Ducharme, M.B.; Brajkovic, D. (2005) Guidelines on the Risk and Time to Frostbite during Exposure to Cold Winds. In Prevention of Cold Injuries (pp. 2-1 – 2-10). Meeting Proceedings RTO-MP-HFM-126, Paper 2. Neuilly-sur-Seine, France: RTO. Available from: http://www.rto.nato.int/abstracts.asp. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 01 MAY 2005 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Guidelines on the Risk and Time to Frostbite during Exposure to Cold Winds 5a. CONTRACT NUMBER