TRG-HSE-017 Basic Training - Extreme Environments - Hot

This course will:​

Temperature & the Human Body

Body Temperature Control

Body Temperature Control

The human body functions within a very narrow temperature range of less than 1°C from 36.5°C to 37.2°C. Outside of this range our cells and enzymes begin to fail.

The body keeps it’s temperature within this range by means of the heat-balance equation:

Heat storage = heat gained – heat loss

Heat is mostly gained from the environment and muscles during exercise.

Heat loss in hot environments is mainly by evaporation of sweat.

When heat gain is greater than heat loss, the body temperature rises above 37.2°C and heat illness occurs.

Methods of Heat Loss/Gain


The transfer of heat to the surrounding environment through electromagnetic radiation. (If the environment is warmer than the body, the body will absorb heat).



The transfer of heat via the skin and object via direct contact.



Cooling of the body when sweat evaporates on the surface of the skin.



Transfer or loss of body heat through the air surrounding the body – such as wind chill or fanning.


Human body Heat Reduction Methods


  • Evaporation: The body's principle method of heat reduction is through the evaporation of sweat. In order to sweat the body needs to be adequately hydrated to compensate for the loss of water through the skin. Without fluid replacement the body will eventually go into shock (heat exhaustion).


  • Convection: Increasing air movement over the skin by wearing loose clothing and fanning will increase the effectiveness of heat loss through sweating.



Body temperature Control

  • The human body is good at adapting to the environment and can withstand 1 degree or more of change without consequence.

Human Heat Reduction Methods

The body's principle method of heat reduction is through  . Increasing  by wearing loose clothing and fanning will increase the effectiveness of heat loss through sweating. 

The Risks of Working in Hot Environments

Risks of Working in Hot Environments

The risks of working in excessively hot (or cold) environments sharply increase as the temperature rises (or falls) beyond a quite narrow range, as seen in the graph. Generally, these risks are:

  • Difficult working conditions
  • Physical fatigue
  • Loss of concentration
  • Reduced work performance
  • Increased accident rate
  • Heat stress & illnesses

Hazards which may increase the risks

There are a number of hazards associated with working in a hot environment which may increase the likelyhood of heat-related illness of an accident:

  • Humidity

  • Individual-specific risk factors (health & lifestyle)

  • Inadequate acclimatisation
  • High work intensity

  • Expectations to perform as in cooler climates

  • Work scheduled during the hottest part of the day

  • Inappropriate clothing

  • Insufficient fluids and rest

  • Working alone


Individual Risk Factors

Certain risk factors present in an individual may further heighten the risk of contracting heat illness: 

  • Being overweight
  • Poor physical fitness
  • Lack of sleep
  • Recent alcohol intake
  • Smoking
  • Dehydration
  • Concurrent illness (e.g. diarrhea)
  • Medications
  • Poor nutritional intake


Which of these are risks of working in hot environments?

  • Physical fatigue
  • Loss of concentration
  • Increased accident rate
  • Increased thirst

Factors which increase the risk of an incident when working in hot environments

  • You can probably work as hard and vigorously as when you're in more moderate climates without putting yourself at additional risk in a hot environment.
  • Ensuring that you stay well-hydrated will lessen the risk of contracting heat-related illness.
  • The amount of rest & sleep you get has no impact on risk to you or the work you preform in hot environments.
  • Coming directly from a significantly cooler environment may also put you at greater risk - including air conditioned environments.
  • The PPE you wear has no influence on how well you're likely to perform in a hot environment.

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Heat-Related Illnesses

Heat-related Illnesses

There are a spectrum of disorders caused by environmental heat exposure. Listed from least to most severe:

  • Heat edema
  • Heat rash
  • Heat syncope
  • Heat exhaustion
  • Heat stroke



Heat Edema


  • Swelling of the lower legs and hands
  • Caused by increased blood flow and vasodilation
  • Feet can feel very heavy and uncomfortable
  • Footwear can become restrictive
  • More common in the early days of acclimatization
  • Usually resolves without treatment
  • Rest and leg elevation will help


Heat Rash


  • Also called ‘prickly heat’
  • Skin irritation caused by excessive sweating and blocked sweat glands of the skin
  • Often occurs in areas where sweat cannot evaporate freely – under clothes
  • Presents as an itchy red pimply rash
  • Usually settles with 7 days and skin peeling can occur as the sweat glands are replaced
  • First Aid: Cool down, wash affected areas. Cream may reduce irritation and itchiness.


Heat Syncope (Fainting)


  • Light headedness, feeling dizzy or fainting in a hot environment.
  • Hot temperatures cause the blood vessels to dilate and this drops the blood pressure.
  • When exerting or standing up too fast, the brain gets insufficient blood which causes the dizziness or fainting.
  • Treatment:
    • Stop the activity and sit or lie the person down.
    • Cool and fan person and rehydrate them with water.
    • If fainting occurs, raise the legs – recovery is usually instant.
  • NB: This is a warning sign of a more serious heat illness and crew must be allowed to rest and cool down for a few hours before returning to duties.



Heat Exhaustion


  • Due to long periods of sweating in hot environments the body looses so much water it goes into hypovolemic shock.
  • Heat exhaustion is a serious condition and requires medical attention.
  • It often presents with feeling dizzy, nausea, rapid pulse rate, fatigue, mild confusion, headache and poor coordination.
  • Treatment:
    • Remove the person from heat to a cool environment. Remove thick clothing and fan them.
    • If able, encourage them to drink water. If they vomit, a drip is usually required to replace the lost fluid and salts.
  • If untreated or if the person continues to be exposed to the hot environment, heat stoke can develop rapidly.


Heat Stroke


  • Heat stoke is a medical emergency.
  • As the shock from heat exhaustion worsens, the body no longer has sufficient water to sweat and therefore cannot cool itself at all.
  • The core temperature raises rapidly to a point where the proteins in the body begin to break down. Death can be rapid.
  • The most common signs are changes in behavior and level of consciousness. Slurred speech and incoordination. Victims may start having seizures.
  • The skin is often dry as there is no longer enough water in the body to produce sweat.
  • The victim requires cooling down very quickly and intravenous fluid replacement.
  • Remove them from the hot environment, remove clothing and wet them with water and begin fanning to increase evaporation and heat loss.
  • Avoid baths of ice water as this may cause the temperature to fall too rapidly.


Rank these heat-related illnesses in order of severity, low to high

  • Heat edema
  • Heat rash
  • Heat syncope
  • Heat exhaustion
  • Heat stroke

Safe Work in Hot Environments

Guidelines for Safe Working in Hot Climates


The following guidelines will aid you in the control and prevention of heat-related hazards & illness:

  • Know the temperature and humidity levels you are working in - temperature monitoring saves lives!
  • Don't work alone, and watch for signs and symptoms of heat illness in your team.
  • Report concerns early.
  • Protect yourself with a hat and sunscreen.
  • Wash and change work clothes regularly to remove sweat and salt crusting layers to improve breathability and cooling.
  • Use fans to increase body heat loss by convection in enclosed areas.
  • Gradually build up to heavy work tasks and plan strenuous activities for cooler times of the day whenever possible.
  • Where appropriate, use power tools or lifting/carrying aids to reduce workload.
  • Schedule frequent rest breaks.
  • Avoid excessive caffeine and sugar which promote dehydration


Heat Index Monitoring


  • Heat index monitoring saves lives.
  • It works out the actual stress index on the body by factoring in the air humidity.
  • The higher the humidity the less effective sweating will be for the body because evaporation is reduced.
  • When the heat stress levels are known – Workers can adapt their work practices and appropriation actions can be taken.


Fluid Hydration

  • Drink water early and often.
  • Aim for one cup (250ml) every 15 minutes in hot climates.
  • Don’t wait to be thirsty to drink water.
  • Aim for pale yellow urine.
  • Water alone is usually adequate – sports drinks are not essential for rehydration.
  • Salt tablets are dangerous and must not be taken.



  • Be aware when travelling from cold climates to hot climates that the body takes about 1-2 weeks to fully acclimatize and adapt to the increased sweating, salt loss and heat stress.
  • Workers in air-conditioned areas will take longer to acclimatize to the hot outside climates.
  • Acclimatization is maintained for about 7 days in cooler climates before being lost (such as when returning home on rotation).