Thailand occupational standard to protect workers from excessive heat

First issued in 1976 and most recently revised in 2016, Thailand's indoor and outdoor occupational heat standard uses the wet bulb globe temperatures (WBGT) as an index to estimate heat stress in the workplace. Specific WBGT temperature limits are given for the intensity of work done. 

The WBGT is a measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle and cloud cover (solar radiation). The WBGT is used as a guide for managing workload in direct sunlight.