Who Can Handle the Heat?

Heat Stress in General Industry

By: Holly Pups, Contributor

Is the risk of heat stress lurking in your facility? The signs of heat stress can be ambiguous, especially in manufacturing settings, which makes recognizing and mitigating the risk difficult. Employees are subjected to extreme temperatures when working around hot machinery, in direct sunlight or in poorly ventilated spaces. Their exposure may be reasonably anticipated, based on facility and weather conditions, or it might be totally unexpected due to an urgent repair or non-routine task.

Heat stress is on OSHA’s radar. Cal/OSHA has had a standard in place for several years, and OSHA announced in 2021 that a federal heat stress standard was already in process. While the standard may take years to come to fruition, OSHA can cite employers for heat-related hazards using the General Duty Clause.

Causes and Symptoms

Before talking about heat within facilities, it’s essential to understand how heat illnesses develop. When the body loses water faster than it’s replaced, it loses its ability to cool itself efficiently. Working in the heat is physically exhausting, and it can also take a toll on an employee’s mental health. Individuals may have a different response to dehydration, and that response can change day to day depending on:

  • Physical condition and ability
  • Personal medical conditions (heart disease, diabetes, pregnancy or medications)
  • Substance use (caffeine, alcohol or drugs)
  • Level of acclimatization to heat sources (new employee, job transfer)
  • Strenuous or dehydrating activities in the days leading up to workday (yard work, exercise, long hours)

How heat stress impacts someone is generally classified as one, or a combination of, the following heat illnesses:

Heat rash: “Prickly heat” is a rash that occurs when skin pores get blocked (typically due to restrictive clothing), and a red rash develops that is hot to the touch.

Heat cramps: Lactic acid builds up in muscles that are not adequately hydrated and causes sudden and excruciating muscle spasms. If left unattended, this build-up can lead to rhabdomyolysis, where muscles break down and cause long-term damage.

Heat exhaustion: When the body exhausts most of its resources, energy reserves are diverted to help the body cool down. This process is characterized by cool, clammy skin and is usually accompanied by a headache, nausea or even feeling “off.”

Heatstroke: Once the body burns through its resource reserves, it can no longer produce sweat and begins to shut down. Sufferers will have hot, red and dry skin. They may have a severe headache, extreme nausea and might not be fully aware of their surroundings. This situation is a medical emergency; trained medical assistance is needed urgently. Heat syncope (fainting) is also associated with heatstroke.

A common misconception about the progression of heat illnesses is that they start at heat rash and work through cramps, exhaustion and finally heat stroke, in that order. Each individual is unique in their responses, so they might skip straight to heat exhaustion or heatstroke.

How can you determine the cause of an employee’s symptoms? Heat illness symptoms are commonly dismissed due to their similarity to other illnesses and personal medical conditions, such as diabetes or high blood pressure.  Are they ill, overtired or dehydrated?

To determine the possible cause, the employer should observe the employee for any symptoms listed above and ask questions about their activities to determine if heat could have played a role. This could include asking:

  • What activities have you been doing today? Where? For how long?
  • Is the task more strenuous than expected?
  • What are the working conditions like?
  • Were you able to take breaks and get a drink when needed?

Hidden Hazards

Where are these heat hazards hiding? The more obvious heat exposures are in facilities such as foundries, metalworking or molding processes where employees interact with the heat sources directly and regularly.

The hazards can be difficult to determine in situations where heat exposure is less obvious. Sometimes a machine goes down, and employees must get the work done. This means they may be subject to unexpected, but strenuous, manual labor. The less obvious areas of risk are where employees are suddenly subjected to unexpected high heat indexes or when doing infrequent or non-routine tasks, such as working in:

  • Permit and non-permit required confined spaces—servicing or cleaning railcars, tanks, pits, silos or manholes
  • Direct sunlight—HVAC repair, servicing roof equipment, landscaping or sidewalk repair
  • Limited ventilation—repairing equipment in boiler rooms, unloading truck trailers or work inside of equipment
  • Heavy personal protective equipment and clothing—welding leathers, arc flash suits or HazMat suits.


What can be done about heat stress? In an ideal world, all work could be completed in a safe and comfortable workplace without putting anyone at risk for heat illnesses (or any other risk for that matter). Since that is not feasible in the real world, the employer must take steps to reduce the risk.

Evaluate the facility where heat may be a problem. The first step in understanding what heat-related hazards exist in the facility is to evaluate them through job hazard analysis, OSHA logs and interviews. Find the heat sources and potential exposures and determine which non-routine tasks put employees at risk.

Eliminate any unnecessary heat hazards. Use engineering controls, when possible, to lower the radiant heat from machinery or to increase airflow.

Develop a heat illness prevention plan. Document, in your prevention plan, how and when to monitor the heat index and know what types of weather events are likely to impact the facility. Include the actions to take before the heat index reaches a dangerous level. Options can include working with a buddy; putting hydration stations closer to the work areas; increasing break time to cool down; and rotating employees through the workspace to shorten their exposures. When high index days are forecasted, encourage employees to stay hydrated in the days leading up to those days.

Acclimatize employees to their work environment. NIOSH recommends new or transferred employees have no more than 20% exposure on their first day and increase by no more than 20% exposure per day until they have adjusted. Employees who have experience working in the heat may start at 50% the first day and work up to an entire shift.

Train employees. The shop floor employees are the company’s first line of defense in recognizing an employee or situation at risk. Conduct heat stress training as part of the onboarding and job transfer process. Teach employees to recognize the signs and symptoms of heat illness and act appropriately. Employees should also know who is trained in first aid and be able to contact them when help is needed.


Heat stress can be a concern in almost any industry. It can be glaringly obvious or leave more subtle clues as to its presence. The effects, should an employee’s struggle go unnoticed, can have serious and even fatal consequences. By assessing the facility, providing training and preparing employees, and monitoring conditions, companies can keep their employees cool, calm and, most importantly, safe.

About the Author:

Holly Pups is an EHS Editor specializing in workplace safety. Holly joined J.J. Keller in 2021 and is a former OSHA Compliance Officer with over a decade of industrial safety experience including warehousing, pharmaceuticals, public sector and plastics manufacturing.

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