They should use appropriate engineering controls, personal protective equipment and work practices to reduce the risk of heat stress. This table gives an approximation of how most people react to heat and humidity. To use the table, find out the temperature and relative humidity of the work area. This number is the temperature-humidity index. The values are for people wearing the right amount of clothing doing light work, with very little wind.
Few people begin to feel uncomfortable.
About half of the people feel uncomfortable. 90 - 104 Sunstroke, heat cramps, and heat exhaustion are possible with prolonged exposure and physical activity. 105 - 129 Sunstroke, heat cramps, or heat exhaustion likely. Heatstroke is possible with prolonged exposure and physical activity. When the THI is 90-104, for moderate to heavy activity, workers should be concerned about heat stress and should alternate time working in the heat and time in cooler areas or light work.