Keep Your Cool Handling Heat Exposure

March 25, 2025|Heat Stress, Industrial Hygiene in the Workplace

By: Ray Chishti, Contributor

As an employer, your role in maintaining a safe work environment is crucial. Did you know that the earth is getting hotter? From 2023 to 2025, the earth has been experiencing monthly record-breaking temperatures. This means ensuring the safety of your employees, especially those exposed to hot temperatures, may be more challenging.

In October 2021, OSHA published an Advance Notice of Proposed Rulemaking (ANPRM) called Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings in the Federal Register. With this publication, OSHA began the rulemaking process to consider a heat-specific workplace standard.

Heat Injury & Illness Prevention in Outdoor & Indoor Work Settings Rulemaking

Whether it’s the result of seasonal fluctuations or the type of work performed at your facility, extreme temperatures can affect the body’s natural ability to handle heat. © KL 1981 – stock.adobe.com

First, consider why OSHA wants to create a heat stress rule. Heat stress is a common threat that could affect any number of employees. However, without a specific regulation, OSHA has relied on the General Duty Clause, which is tough to enforce.

The General Duty Clause allows OSHA to cite employers for recognized hazards if there’s a feasible method to correct them. That’s a bit oversimplified, but the key challenge for OSHA is recognition.

The risk of any employee suffering heat stress depends on several factors, many of which are personal issues, like weight and health conditions. So, even when OSHA responds to a hospitalization due to heat stress, the agency hasn’t always been able to issue a citation.

By creating a rule requiring specific employer obligations, OSHA can more easily issue citations. For example, if the rule requires a written plan and employee training, but you don’t have one, then OSHA could issue a citation—even if none of your employees suffered from heat stress.

Or, suppose OSHA questions your employees about their training, like recognizing signs of heat stress. If the employees cannot answer those questions, OSHA can cite a training violation—even if you wave a piece of paper showing that the employee attended the training.

Assessing Temperature Extremes

Working in hot temperatures puts an extra strain on an employee’s body. With some understanding of how the body reacts to heat, they can prevent injuries.

Age, weight, degree of physical fitness, metabolism, medications, use of alcohol or drugs, water consumption, caffeine consumption and various medical conditions (such as hypertension) all affect a person’s sensitivity to heat. It is difficult to predict who will be affected by the heat and/or when someone will be affected.

Other factors to consider during temperature extreme assessments are air temperature, humidity, radiant heat from the sun and other sources, conductive heat sources (i.e., ground, air movement) workload severity and duration, protective clothing and PPE.

It’s also important to consider whether or not employees are accustomed to the heat or cold. By gradually being exposed to working in hot or cold conditions, an employee’s body develops a greater tolerance for working in extreme temperatures.

Personal Protective Equipment

When assessing a hot work environment, various risk factors must be considered, including physical and environmental factors. © charnsitr – stock.adobe.com

Whether it’s the result of seasonal fluctuations or the type of work performed at your facility, extreme temperatures can affect the body’s natural ability to handle heat, leading to heat illness. Protection against the sun’s UV rays is also essential for workers. It can help employees avoid heat rash and sunburn. Of course, sunscreen works, but wearing the right clothes can be just as effective. For example, you can have employees wear:

Loose-fitting long-sleeve shirts or pants;
A cap with a wide brim to protect the neck, ears, eyes, nose, head, forehead; and
Sunglasses that block up to 100% of UV rays.

Remember, during the summer, strong sun rays, not just heat, can be hazardous to employee health if not addressed. It’s crucial to ensure your employees are well-protected. Have them wear:

Light-colored, loose-fitting, breathable clothes—cotton is always a good option,
Short sleeves and shorts while indoors or outdoors, and
Bandanas (where feasible) to protect from sweat.

Keep in mind that you can also assign PPE. Warm-weather PPE includes:

Portable ice packs,
Cooling vests,
Cooling towels,
Cooling bandanas and
Portable water packs.

Evaporative Heat Control

Moisture-wicking fabrics, ice vests, cooling towels and bandanas help provide workers with a cooling effect, like what happens when a person sweats. While sweating, heat is lost from the body when sweat evaporates from the skin’s surface. The body naturally reduces heat, depending on air movement over the skin and the amount of humidity in the air.

As moisture evaporates from these types of cooling PPE, it provides a cooling sensation to workers.

Consider the Risk Factors

When assessing a hot work environment, various risk factors must be considered. Physical aspects, such as age, weight, fitness level, health conditions and metabolism, can influence an individual’s heat sensitivity. Environmental factors also play a significant role, including air temperature, humidity, radiant heat, conductive heat sources, clothing and PPE.

Written Temperature Extreme Management Plan

A temperature extreme management plan establishes guidelines to be followed by employees who work in extreme temperatures. The effectiveness of the plan depends upon the support of employees. While this plan establishes guidelines and gives you sample procedures, you must decide how best to develop and implement your own written temperature extreme management plan.

Classify the Work

There’s more to measuring heat exposure than simply sampling the air temperature. The type of work being performed also impacts the body’s ability to handle heat. Work can be classified as light, moderate or heavy, depending on the metabolic energy required.

For example:

Light hand work–writing
Heavy hand work–typing
Heavy work with one arm–hammering nails
Light work with two arms–filing metal
Moderate work with the body–cleaning the floor
Heavy work with the body–digging

Balance the Heat

Based on the National Institute for Occupational Safety and Health’s (NIOSH) dry bulb temperature measurement—which measures ambient air with a thermometer—most people feel comfortable at 71.6^o-77.9^oF while performing light work. However, as work intensity is increased, the air temperature needs to be decreased to maintain a comfortable temperature.

For work environments where high humidity and low air speed are factors, NIOSH determined that 86^oF is the maximum temperature for light work before performance is affected. For moderate levels of physical work, 82.4^oF is the upper limit. Based on these wet bulb temperature measurements—which use an instrument to measure humidity—temperatures that reach beyond these threshold values could result in decreased employee performance, increased accidents and heat illness. IHW

About the Author:

Ray Chishti joined J. J. Keller & Associates, Inc. in 2017 as works as a Senior Editor. Previously, Ray worked as an EH&S professional in auditing, management and executive leadership positions with new construction, operating facilities and large EPC projects valued between $1-2 billion. He has 20 years of EH&S experience in various industries, including fossil fuel power plants, and utility distribution and transmission work. He holds a Juris Doctor with a concentration in Occupational Safety and Health. Ray is also an OSHA-authorized trainer for general industry and construction and has first aid, AED and CPR certifications.