Heat Stress

Safety Training Handout


How does the body respond to heat?

  • The body tries to maintain a constant internal temperature by getting rid of excess heat
  • It uses two methods to get rid of heat: (1) increasing blood flow to skin surface and (2) sweating
  • Increasing blood flow to the skin surface means less blood flow to the brain and active muscles, which can cause reduced mental alertness & comprehension, fatigue, weakness, loss of strength
  • Sweating can cause objects to become slippery, increasing chances of an accident

Why do the body’s cooling mechanisms sometimes fail?

  • High air temperature reduces effectiveness of heat release
  • High humidity reduces evaporation of sweat
  • Sweating leads to excess loss of fluid
  • Sweating leads to excess loss of sodium

What factors contribute to heat-related illness?

  • Environmental factors: Air temperature, humidity, radiant heat sources, air circulation
  • Physical work factors:  (1) type of work, level of physical activity and duration, and (2) clothing color, weight, and breathability
  • Personal factors: Age, weight/fitness, drug/alcohol use, prior heat-related illness

Recognizing and treating the most common heat disorders



Signs & symptoms


Heat stroke

Total breakdown of body’s cooling system

High body temp (>103), sweating stops and skin is hot red and dry; headache, dizziness, weakness, rapid pulse

Treat as a medical emergency; move victim to cool area, immerse victim in cool water or massage victim’s body with ice; do not give liquids

Heat exhaustion

Excessive loss of water and salt

Heavy sweating, intense thirst, skin is pale and cool, rapid pulse, fatigue/weakness, nausea & vomiting, headache, blurred vision, fainting

Move to cool area, rest with legs elevated, loosen clothing, drink plenty of fluids

Heat cramps

Excessive loss of water and salt

Painful spasms in arms, legs and abdomen; hot, moist skin

Drink fluids, massage cramped areas, rest


Excessive loss of water and salt

Fatigue, weakness, dry mouth

Drink fluids and replace salt

Heat rash

Clogged sweat glands

Rash of pink pimples, intense itching, tingling

Cleanse area & dry; apply calamine or other lotion.

What can be done to prevent heat–related illness?

  • Drink plenty of fluids:  5-7 ounces every 20 minutes
  • Give your body time to adjust to the heat: most workers require 3-5 days – so go slow
  • Choose proper clothing: Wear light colors if working outside and choose lightweight/breathable material
  • Try to perform your most strenuous activities in the early morning/early evening
  • Use work/rest cycles when possible to give your body time to recover
  • Eat properly: Save biggest meal until evening