![]() Heat sources - Weather reports cannot account for the heat generated by fires, hot tar or other materials, ovens, or other hot equipment, or heat-absorbing surfaces such as roads and roof surfaces.Direct sunlight can increase Heat Index by up to 13.5☏ (7.5☌). Work in the sun may be considerably hotter. Direct sunlight - Weather services measure temperature and Heat Index in the shade.Indoor work - A weather report cannot gauge conditions inside a building.In addition to possible distance-based errors, weather reports can be inaccurate if the worksite has features that affect heat conditions. The potential error increases with distance from the weather station. Heat conditions at the worksite may be different for multiple reasons, from cloud cover and humidity to local heat sinks. While local weather reports based on meteorological data from observation stations can be useful, the readings from these stations may not reflect the conditions at the specific worksite. Use of heat index is a less desirable substitute. Workplace environmental heat should be measured on-site using WBGT meters. All these factors can influence the total heat stress experienced by workers. Air (dry bulb) temperature also ignore relative humidity. The heat index does not account for the effects of wind, sunlight, radiant heat sources, or workload. It is measured in the shade and combines air temperature and relative humidity to represent how hot the conditions feel at rest. Heat Index is another common way to measure heat stress. In contrast, standard thermometers only assess one factor (air temperature). One major advantage is that WBGT accounts for all four major environmental heat factors - temperature, humidity, radiant heat, and wind. WBGT has important advantages over other environmental heat measurements. Employers should always follow the WBGT manufacturer's instructions about setup, calibration, and use. For example, if the work is in direct sunlight, then the WBGT instrument should be in the sun. The WBGT instrument should be placed close to the work location. A black globe thermometer to measure radiant heat.A natural wet bulb thermometer to measure the potential for evaporative cooling.A dry bulb thermometer to measure the ambient air temperature.WBGT devices contain three different thermometers: OSHA recommends the use of wet bulb globe temperature (WBGT) monitor to measure workplace environmental heat. In most situations, wind helps workers cool off.Īn environmental heat assessment should account for all of these factors. Radiant heat from sunlight or artificial heat sources such as furnaces.High relative humidity makes it difficult for the body to cool itself through sweating. Four factors contribute to heat stress in workers: Environmental HeatĮnvironmental heat is more than just temperature. Sports physiologists recognize that heat-related illness may occur, surprisingly, at low to moderate temperatures, including below 65☏ when workload is very heavy (Armstrong 2007). Remember: Physical labor increases the heat experienced by workers. They should know that workers may experience heat stress at temperatures much lower than public heat advisories. Employers should be aware of any heat advisories from the National Weather Service. This step allows employers to determine if the work conditions are too hot. To determine workers' total heat stress, employers must assess both of the above heat sources.Įmployers should compare the total heat stress to published occupational heat guidance. ![]() Metabolic heat, generated by the body, is related to workload (physical activity).Environmental heat is produced by warm or hot surroundings.Two heat sources contribute to the risk of heat-related illness. Heat-related illness prevention starts by determining if a heat hazard is present in the workplace. You should consider the above factors when evaluating heat stress risk to workers. Common values given for categories of work are included in the table on Workload. Workload considerations are described at length in the OSHA Technical Manual. Use of clothing or protective gear that can reduce the body’s ability to lose excess heat.Level of physical activity, i.e., the workload leading to body heat production.Presence of heat sources (e.g., hot tar ovens or furnaces) in the work area.Environmental conditions (such as air temperature, humidity, sunlight, and air speed), especially on sequential days.There are many factors that have a role in creating an occupational heat stress risk to workers.
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