Working Safe in the Heat

Working safely in the heat

Recognize and Prevent Heat Stress

It’s tougher to beat the heat on job sites than at backyard barbecues. TEAMates need to be informed and equipped to take preventative measures against heat stress, such as finding shade, drinking plenty of water, wearing loose and light clothing, and/or taking regular breaks.

As safety professionals we know that exposure to hot conditions presents a real threat to TEAMates. According to the most recent U.S. Heat Fatalities Map from the Occupational Safety and Health Administration (OSHA), there were 109 heat-related occupational fatalities between 2008 and 2014.

Agriculture and construction workers typically run the highest risk of experiencing heat-related problems. In a 2017 Professional Safety article, “Fire and Ice: Protecting Workers in Extreme Temperatures,” the author notes,”… that construction in particular is an industry where fast-track projects must continue even in adverse weather conditions.”

Heat Stress

“Heat stress” is a term that encompasses many different physical reactions that result from a body’s attempt to regulate its temperature in response to the environment. These physical reactions range from uncomfortable to fatal, and tend to exacerbate other workplace risks.

“All of these types of issues can help create safety hazards for both the worker and their co-workers.”

Common symptoms of heat stress include:

  • Heat rash due to sweating and clogged pores
  • Heat cramps due to the loss of electrolytes from sweat
  • Heat exhaustion

These issues might not seem particularly threatening on the surface. However, they often lead to worker irritability, low morale, absenteeism and shortcuts in procedures.

On the other end of the spectrum, heat stroke is a true medical emergency. Heat stroke occurs when the body becomes unable to regulate its temperature, and the condition can be fatal.

Risk Factors

Certain environmental, physical and operational variables affect the ease with which heat-related hazards can be addressed.

Of primary concern is to maintain the body’s core temperature at or near the normal level, which is approximately 98.6 degrees Fahrenheit.

Risk factors inhibiting this objective include:

  • The temperature of the work site
  • The environment’s relative humidity
  • Personal protective equipment (PPE) that interferes with the body’s ability to sweat effectively
  • An employee’s workload (the body produces heat during muscular exertion)
  • An employee’s age, drug use, body weight, cardiovascular fitness, underlying health problems, and existing burns (these may damage or destroy sweat glands)
  • A lack of worker and supervisor training on heat stress

First Signs

There are several technical methods of assessing the risk of heat stress for a general employee population. One is to examine the wet bulb globe temperature (WBGT) of a work environment. This considers the temperature, humidity, air movement, and radiant heat sources – compared with the occupational exposure limits (OELs) recommended by organizations such as the National Institute for Occupational Safety and Health (NIOSH).

Another, and much more simple method, is to utilize the free Occupational Health and Safety App. This can help determine the likelihood of heat stress using relative humidity and temperature data. This system is far more field friendly than using the WBGT.

Observational indicators of heat stress may be less scientific, but it is still worthwhile for workers and frontline supervisors to learn how to keep a watchful eye. Not only are they easier to use in assessing individuals, but they can be identified more quickly and yield a faster response. There are free and helpful tools available to assist with these efforts. The OSHA and NIOSH App (OSHA-NIOSH Heat Safety Tool App) features real-time heat index information, precautionary recommendations based on weather conditions, and a guide for identifying signs and symptoms of heat-related illnesses, at the work sites precise location.

TEAMates and supervisors should also learn to watch for the following signs of heat stress:

  • Sudden, severe nausea or headaches
  • Increased incidents or absenteeism
  • Chronic fatigue
  • A lack of alertness

Methods for Prevention

Mitigating heat exposure risks begins with a high-quality training program. TEAMates need to understand the danger of heat stress – the signs, the symptoms, and prevention. Supervisors need all the worker training, plus they need to understand the need for fluid replacement, know how to adjust expectations for non-acclimatized workers, and learn the importance of removing workers at the first signs of heat illness.

Once TEAMates have been properly informed, they should be well-equipped for the day-to-day work of protecting themselves from hot temperatures. For supervisors, maintaining TEAMate acclimatization is one of the most important things to cover. “Acclimatization” refers to the beneficial physiological adaptations that occur as a result of frequent exposure to hot environments. These adaptations take from 7 to 10 days to develop, and include more efficient sweating, stabilized circulation and the ability to work with a lower heart rate.

According to NIOSH, workers can maintain their acclimatization over a weekend, but they may need supervisors to help them gradually reacclimate to environmental conditions if they are absent for a week or more. OSHA recommends that new workers and those returning from a break should begin with 20 percent of their usual workload on their first day, increasing by no more than 20 percent on each subsequent day. In the case of a rapid temperature change, OSHA says an appropriate acclimatization program might require even experienced workers to start with 50 percent of their normal workload, increase to 60 percent on the second day, 80 percent on the third day and 100 percent on the fourth day.  Remember, these recommendations are in place for work situations where consecutive days are in the high heat caution ranges.

Important daily tasks for heat stress prevention might include:

  • Evaluating work site conditions and assessing heat risks
  • Ensuring that water is available and water coolers are sanitary
  • Actively encouraging workers to take regular drinks of water
  • Scheduling hot or physically demanding jobs for the coolest parts of the day
  • Implementing mandatory work/rest schedules
  • Creating a “buddy system” for workers to watch out for each other
  • Installing shade canopies
  • Providing air-conditioned trailers or break rooms for spot cooling
  • Utilizing vented, full-brim hard hats and other types of warm-weather PPE

Finally, as summer winds down you may think that it has “cooled” down a bit, however, don’t think that heat stress is no longer a concern. In the chart to the left you can see that when temperatures are “cooler” and the relative humidity is high, there can STILL be an impact to your exposures to heat stress related issues that you may not even realize.


  • Take breaks in shady/cool places
  • Stay hydrated with water or sports drinks, usually best to consume water to sports drinks at a 3 to 1 ratio
  • Limit caffeine & nicotine intake as these can dehydrate and increase blood pressure
  • Wear cooling clothing appropriate for the work environment
  • Use approved cooling towels or bandanas
  • Watch out for one another and be alert for those early symptoms
  • Recognize early possible symptoms of slurred speech or confusion, headaches, dizziness, clammy skin, being out of breath, and/or muscle cramps.
  • This can apply at work AND at home when doing yard work or any outdoor activities!

Enjoy the rest of the Summer and remember:  Heat Stress can affect you not only at work but also at play and while working around home. Follow the guidelines listed above and they will help you and your family enjoy the wonderful Summer season.