Understanding Heat Load When Wearing Personal Protective Clothing — Occupational Health and Safety

Understanding Heat Load When Wearing Personal Protective Clothing

PPE can affect employees who work in the heat.


Environmental factors (for example, humidity, wind, temperature, radiant heat, clothing, and workload i.e. metabolic rate) are considered to determine if a risk of heat is present inside or outside. There is no doubt that heat stress negatively affects many workers and the additional heat load of protective clothing increases the risk. The ACGIH Threshold Limit Values ​​and the National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Levels (RELs) for heat stress are two guidance documents for assessing heat stress. Adjustment factors were evaluated to reflect the change in heat stress imposed by different sets of clothing. While some clothing fit factors (CAFs) have been calculated with limited experimental data and some professional judgment, laboratory heat balance methods have yielded better estimates for a wider selection of clothing ensembles. These experiments provide the starting point for evaluating workwear and personal protective clothing in heat balance assessments based on sweat and heart rate, blood pressure and skin temperature. The CAFs proposed in the ACGIH TLVs and the NIOSH REL provide a framework for redesigning a corrected wet-bulb thermometer (WBGT) measurement based on work activity, environment, human physiology, frequency and duration of exposure.


Anyone who has worked in industry indoors while wearing personal protective clothing knows the added heat load during summer or working outdoors in a hot indoor environment. The National Institute for Occupational Safety and Health (NIOSH) and other researchers have looked at the increased risk of heat stress when wearing different types of personal protective equipment (PPE). Wearing PPE can often increase the risk of heat-related illnesses by raising blood pressure and core body temperature (i.e. core temperature) faster than wearing other types of PPE ample in the same work environment. Some information is discussed in the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values ​​literature for heat stress and strain, but does not address the additional metabolic heat load due to wearing PPE and the need to correct environmental measures.

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