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Preventing and Responding to Heat Illness

Best Practises - Your Written Program

I. Effective Work Practices

6. Extra Measures During Heat Waves

Because of extreme environmental conditions during a heat wave, employees' physical and mental condition can change rapidly into a serious medical condition. The onset of heat illness may be confused with other problems and may not always be obvious before it becomes life-threatening. Therefore, extra measures may be required to prevent and/or respond to heat illness.

Smart Tips

Extra Measures During Heat Waves

Extra Vigilance - Real Time Communication and the "Buddy System" - during a heat wave it is necessary to be extra vigilant. Your real time communication system and your "buddy system" are especially important to get more frequent feedback from your employees and supervisors in the field. Then, based on the environmental conditions present and the condition of your employees you can more quickly make the appropriate adjustments, communicate them, and put the changes into place before problems arise or become serious. In a heat wave:

  • Do not allow employees to work alone
  • Designate a person(s) to closely monitor and frequently report on employees' physical and mental condition.
  • Have supervisors and employees watch each other very closely using your "buddy system", and encourage them to communicate about how they are feeling on a frequent basis
  • Account for the whereabouts of employees at more frequent intervals throughout the work shift and at the end of the work shift.

Additional Water Consumption

  • Encourage employees to drink small quantities of water more frequently (i.e., in addition to the four 8-ounce glasses of water, or a total of one quart per hour) throughout the entire work shift to prevent dehydration
  • Have effective replenishment measures in place for the provision of extra drinking water to ensure that supplies are reliable
  • Ensure that employees replace lost salts and minerals from the added fluid loss.
  • Encourage employees to consult with their doctor on salt and mineral replacement.
  • Encourage workers to also drink water before and after work

Additional Cooling Measures - Remember that shade is adequate only when it completely blocks the direct sunlight and allows the body to cool. Shade is not adequate when it does not allow the body to cool. In a heat wave air temperatures in the shade may still be extremely high and not allow the body to cool. During a heat wave, you may need to use other alternative cooling measures in addition to shade, (e.g. allowing employees to spend time in air conditioned places or having them spray themselves with water). Provide Cooling Using Alternative Measures.

Additional and/or Longer Rest Breaks - During a heat wave, it is especially important to permit employees the freedom to interrupt work activities to take rest breaks and allow the body to cool. During a heat wave you may need to allow employees to take more frequent and longer breaks. Remember to provide areas for employees to take their breaks which are:

  • Readily accessible
  • Open to the air and ventilated or cooled, or in shaded areas
  • Near sufficient supplies of drinking water

Changing Work Scheduling and Assignments - during a heat wave you may need to put into place one or more or the following additional measures:

  • Start the work shift even earlier in the day or later in the evening
  • Split-up work shifts to avoid work during the hottest part of the day
  • Cut work shifts short or stop work altogether
  • Reduce the severity of work by scheduling slower paced, less physically demanding work during the hot parts of the day and the heaviest work activities during the cooler parts of the day (early-morning or evening)


Remember, even employees who were previously fully acclimatized are at risk for heat illness during a heat wave. This is because during a heat wave the body does not have enough time to adjust to a sudden, abnormally high temperature or other extreme conditions.

Changing Meals

  • Encourage employees to eat smaller more frequent meals which reduce the heat the body produces as compared to eating large meals less frequently
  • Encourage employees to choose foods with higher water content such as fruits, vegetables and salads