Heat Stress

An overview on heat stress, how to spot and prevent it at work.

construction worker drinking water due to heat under the sun

Published 8 Sep 2022

What is Heat Stress?

Heat stress is the effect of heat load on a worker’s body from exposure to a combination of factors such as the environment, metabolic heat, and clothing. Heat stress causes the body to lose the ability to control heat and can lead to heat exhaustion and heat stroke.

What are The Causes of Heat Stress?

There are various causes of heat stress which can be categorized into 3 sources:

3 Major Sources of Heat

  • Environmental factors – These are the high-temperature workplaces that can either be indoors or outdoors. Working in indoor areas such as bakeries, foundries, factories, and furnaces or in outdoor sites such as construction, road, mining, and agriculture can make the worker more susceptible to heat stress. Other environmental factors that can cause heat stress are weather or seasonal changes such as summer, as well as places high with humidity such as kitchens and laundries.
  • Metabolic heat – This is the heat generated by a person’s body during physical activity. Metabolic heat is ,in simple terms, internal heat. There are 3 ways the body can exchange heat with its surroundings, which are radiation, convection, and evaporation of sweat.  Radiation is heat transfer from a source of heat, usually associated with the sun. Convection is the process wherein the body exchanges heat through the surrounding air. Lastly, the body cools itself through sweat evaporation. However, cooling through sweat is limited in areas with high humidity since the air can’t easily accept more moisture.
  • Clothing – Employees should avoid wearing extra layers of clothing and clothing that absorbs heat. Their clothing should be made up of materials that can reflect heat and are appropriate for their workplace and tasks. 

What are The Symptoms of Heat Stress?

People that have heat stress will commonly experience heat rash, muscle cramps, and severe thirst.  Other symptoms include:

  • Dizziness
  • Headache
  • Body ache
  • Fatigue
  • Rapid heartbeat
  • Nausea
  • Chest pain
  • Labored breathing

If heat stress is left untreated,  it can lead to illnesses such as heat exhaustion or heat stroke. The two heat-related illnesses have different symptoms, which are:

Heat Exhaustion

  • Loss of body water and salt through excessive sweating
  • Dizziness
  • Muddled vision
  • Fatigue
  • Severe thirst
  • Headache
  • Nausea and vomiting
  • Diarrhea 
  • Muscle cramps
  • Labored breathing
  • Palpitations
  • Tingling and numbness of hands and feet

Heat Stroke (severe heat illness)

When heat exhaustion develops into heat stroke, call for medical help as soon as possible.  What you can do: Move the worker to a cooler place, remove clothing, wet the person’s skin, apply cold wet cloths to the body, and anything to reduce the worker’s temperature before the ambulance arrives. The symptoms of heat stroke include:

  • Body temperature greater than 41°C
  • Complete or partial unconsciousness
  • Confusion
  • Hot, dry, or heavy sweating
  • Seizures

How to Prevent Heat Stress?

Prevent heat stress in the workplace by ensuring that the environmental factors, metabolic heat (physical activity), and clothing are monitored. Here are some guidelines employers can adopt for their workers:

how to prevent heat stress

  • Provide water or other beverages (preferably cold drinks).
  • Provide a shaded area or a place that is cooler in temperature.
  • Discourage workers from drinking caffeinated or alcoholic beverages during work hours.
  • Prepare clothing fit for the weather and the type of work such as providing a hat or cooling gear.
  • Schedule periodic breaks.
  • Allow employees to acclimate by gradually increasing workload (metabolic heat) and heat exposure.

Occupational Heat Stress Requirements

To supplement existing requirements, OSHA is developing a new heat standard to include indoor workers who are not in climate controlled environments. OSHA highly suggests to keep the temperature between 68-78°F (20-25°C). Companies should have the initiative to develop plans to prevent heat stress and other illnesses due to hazardous heat conditions.

How iAuditor Can Help to Protect Workers From Heat Stress

Employers can start their heat control programs by using digital tools and incorporating heat exposure checklists. The template can be used during toolbox talks, an essential tool most commonly used by the construction industry. All of these are possible with the leading health and safety app, iAuditor by SafetyCulture

iAuditor features for heat control include:

  • Alerts for Issues – Immediately get notified when a problem arises.
  • Corrective Action – Workers can suggest corrective actions during an inspection.
  • Data Insight – Check if there are repetitive issues which can help pinpoint root causes.