Protect Your Workers in Hot Weather!

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Heat and humidity can create health risks for employees who work outdoors. Employees exposed to excessive heat may develop heat stress. This article will explain what heat stress is, who is susceptible to it, and what you can do to prevent it.

Types of Heat Stress

Heat stress is a collective term used to describe various heat-related conditions. The CDC identifies five types of heat stress. These are outlined below.

The conditions are listed in order of severity beginning with the most serious.
  • Heat Stroke occurs when the body's cooling systems shuts down. This condition is dangerous because a person's body temperature can become high enough to cause death. Symptoms may include hot, dry skin, hallucinations, headache and confusion.
  • Heat Exhaustion results from the loss of water and sodium through excessive sweating. Symptoms may include dizziness, weakness, nausea and clammy skin.
  • Heat Syncope means fainting caused by excessive heat. Fainting may occur if a person has been standing for a prolonged period, or if he or she suddenly rises after sitting or lying down.
  • Heat Cramps are muscle cramps caused by a loss of water and sodium.
  • Heat Rash is an irritation of the skin caused by excessive sweating.

The more severe types of heat stress (particularly heat stroke and heat exhaustion) require immediate medical treatment. Some employees affected by heat stress may lose work time. A heat-related illness that arises out of employment will likely qualify as an occupational disease or injury.

Thus, workers who sustain heat stress on the job should be eligible for workers compensation benefits.

Heat Index

Two factors contribute to heat-related illnesses: heat and humidity. Heat stress can result from exposure to hot dry air or to warm air that is high in humidity. If the air temperature remains constant, a person will generally feel progressively hotter as the humidity rises. This is because humidity can impair the body's cooling system. The body cools itself through the evaporation of sweat. When the humidity is high, evaporation slows and the body's cooling system is less effective.

The National Oceanographic and Atmospheric Administration (NOAA) has developed a useful metric called the heat index. The index combines both heat and humidity. The NOAA's heat index chart (available at the its website) can be used to assess outdoor conditions. The chart is color-coded to show the relative degree of risk at various combinations of heat and humidity from yellow (caution) to red (extreme danger).

Who is at Risk?

Virtually anyone who works outdoors in hot weather may suffer heat stress. However, some workers are particularly vulnerable. These include workers who:
  • perform strenuous work or work for an extended period of time in a hot environment
  • are exposed to direct sunlight. Sunshine raises the air temperature.
  • wear heavy clothing or clothing that doesn't "breathe"
  • are older or have certain medical conditions like high blood pressure, heart disease or diabetes


Here are some steps you can take to keep your workers safe in hot weather:
  • Water Provide easy access to water. The amount needed rises with the heat index.
  • Shade If possible, provide employees a shaded place to work.
  • Rest Workers need more frequent breaks as the heat index rises. Rest areas should be in full shade.
  • Acclimatization Workers develop a tolerance for heat over time. New workers or those who have been away from work (due to a vacation or other reason) may need a week or so to acclimatize.
  • Training Educate your workers to recognize the signs of heat illness. Workers should monitor themselves and each other.
  • Weather Pay attention to weather forecasts so you and your employees know when the heat index will be high.


Both OSHA and the CDC provide advice on how to safeguard workers from heat stress. Check their websites (see links below). OSHA's site offers checklists, training guides and first aid tips. For additional information about preventing heat stress contact your workers compensation insurer.
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