Use of Humidex to Set Thermal Work Limits for Emergency Workers in Protective Clothing
Abstract
Humidex (HD) is a temperature-humidity index used to provide guidance concerning heat hazards based on normal activities and clothing. Personnel responding to security or NBC threats often wear body armor or protective clothing which can impose a greater heat burden. Our proposal was to use HD to provide short-term guidance for specialized clothing. Our Heat Strain Decision Aid model was used to calculate rectal temperature (Tre) values for combinations of temperature and humidity. Corresponding HD values were calculated using Ta, Tdp, and constants for other inputs. Activity levels were light (139 W m-2), medium (236 W m-2) and heavy (333 W m-2). Equations were calculated for the relationship between Tre and HD. The mean R2 value for 24 polynomial equations was 0.97. To evaluate the utility of the prediction, the difference between Tre predicted by the equation and the model was calculated. The average maximum difference was 0.71 C. There was a clear relationship between HD and predicted thermal strain, but differences increase as Tre increases, until some differences fall outside of acceptable levels. For general use, the upper limit of the relationship between HD and Tre could be used to set conservative guidelines for a given level of thermal strain (Tre) and activity, but for true emergencies, better guidance is necessary.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 2005
- Accession Number
- ADA474458
Entities
People
- R. F. Wallace
- W. R. Santee
Organizations
- United States Army Research Institute of Environmental Medicine