Think LSR – Heat Stress Can Kill! Do You Know The Signs?

Think LSR – Heat Stress Can Kill! Do You Know The Signs?


Heat stress occurs when the body’s means of controlling its internal temperature starts to fail. As well as air temperature, factors such as work rate, humidity and clothing worn while working may lead to heat stress.


Your body reacts to heat by increasing the blood flow to the skin’s surface, and by sweating. This results in cooling as sweat evaporates from the body’s surface and heat is carried to the surface of the body from within by the increased blood flow. Heat can also be lost by radiation and convection from the body’s surface.


Someone wearing protective clothing and performing heavy work in hot and humid conditions could be at risk of heat stress because:

  • Sweat evaporation is restricted by the type of clothing and the humidity of the environment
  • Heat will be produced within the body due to the work rate and, if insufficient heat is lost, the core body temperature will rise
  • As the core body temperature rises the body increases the amount of sweat produced, which may lead to dehydration
  • The heart rate also increases, which puts additional strain on the body
  • If the body is gaining more heat than it can lose, the core body temperature will continue to rise
  • Eventually it reaches a point where the body’s control mechanism itself starts to fail


Heat stress can affect individuals in different ways, and some people are more susceptible to it than others.

Typical symptoms are:

  • An inability to concentrate
  • Muscle cramps
  • Heat rash
  • Severe thirst – a late symptom of heat stress
  • Fainting
  • Heat exhaustion – fatigue, giddiness, nausea, headache, moist skin
  • Heat stroke – hot, dry skin, confusion, convulsions and eventual loss of consciousness. – This is the most severe disorder and can result in death if not detected at an early stage

The effects of heat stress can be divided into three distinct conditions:

  1. Heat cramps
  2. Heat exhaustion
  3. Heat stroke – this is a SERIOUS condition which can KILL if not treated!


Limit the length of time that you are exposed to hot conditions. Ensure regular breaks in the shade or in cool air.

Use mechanical aids to reduce the level of physically demanding work – this will help to reduce the impact of hot environments, especially when you are wearing a lot of clothing or equipment.
Keep yourself hydrated – drink plenty of water.

If working in an enclosed space, ensure that the space is ventilated as well as possible. Wear light clothing to allow the largest possible surface for free evaporation of sweat.

In tropical areas especially, exposure to the sun should be avoided as far as possible, particularly during the hottest part of the day. When it is necessary to work in exceptionally hot or humid conditions, appropriate clothing (including a hat) offering protection to both body and head should be worn. Light cotton clothing will reflect the heat and help to keep the body temperature down. Keep the upper body covered, especially around midday when the sun is at its strongest. Skin that has not been exposed to the sun for several months burns very easily.

Do not forget environmental factors when creating risk assessments.

Stay Cool – TH!NK LSR!

Peter Chilman, QSE Manager