Table 5.
Considerations in Monitoring Environmental Conditions for Occupational Heat‐Hazard Assessments
| Monitoring weather variables | Advantages | Disadvantages | Adjustments | |
|---|---|---|---|---|
| Location | On‐site with portable weather sensor at 1.1 m height | Best represents workers' environmental conditions; provides accurate classification of heat exposure | Cost of portable sensor, maintenance, ease of use | |
| Off‐site weather station observations or model output | Low‐cost/free, ease of use via apps | May not be representative of local conditions, leading to misclassification of heat exposure | Interpolate values from 2 or 3 weather stations | |
| Indices calculated from environmental measures | WBGT industry standard | Combines multiple meteorological variables for a more comprehensive heat stress measure | Monitoring equipment costs; lower‐cost equipment may be less accurate | Must account for clothing adjustment factor; acclimatization; metabolic load |
| Indices calculated from heat balance models | Heat indexa | Simple to determine; widely available; widely used unit; broadly known | Solar, clothing, and activity assumptions not representative of most working conditions; does not work in very dry climates (avoid use) | Add solar factor and adjustments for metabolic rate and clothing |
| UTCI | Publicly available version (regressions) simple to determine, widely used unit (°C). Accounts for the full environment | Built to assess thermal stress in average person; not developed for working population; does not yet have adjustments for metabolic rate | Clothing is adapted based on air temperature (0.30–2.6clo range) | |
| PET | Publicly available software easy to use, widely used unit (°C). Accounts for the full environment. Use mPET if making calculations for workers | Built to assess thermal comfort for an average person; assumes “light activity” and that one is not moving with constant clothing (0.9clo). Cannot modify clothing or METs | ||
Abbreviations: MET, metabolic equivalent of task; mPET, modified physiological equivalent temperature; PET, physiological equivalent temperature; UTCI, universal thermal climate index; Apps, applications; WBGT, wet bulb globe temperature.
a
Basic rational index simplified from its original version (apparent temperature) and derived from only air temperature and humidity in its current form.