The Wet Bulb Globe Temperature (WBGT) is the primary index used by OSHA, NIOSH, and ACGIH for assessing heat stress in occupational settings. It accounts for temperature, humidity, air movement, and radiant heat.
Standards
- OSHA Technical Manual Section III, Chapter 4
- NIOSH Criteria for Hot Environments (2016)
- ACGIH TLV Documentation
Measurement Components
- Wet Bulb: Measures sweat's cooling effectiveness
- Globe: Measures radiant heat from sun/equipment
- Dry Bulb: Standard air temperature
Key Concepts
- TLV: Threshold Limit Value - maximum safe WBGT
- Action Limit: 90% of TLV - triggers precautions
- Acclimatization: 5-7 days exposure increases tolerance
Measurement Tips
- Use a WBGT meter with all three thermometers
- Measure at worker's head level in the hottest area
- Take readings at least hourly during hot periods
- Add clothing adjustment for protective equipment