Hot Temperatures

Hot Temperatures

Now that the temperatures are starting to get up to twenty degrees Celsius, it is time to start reminding staff of the hazards of working in hot weather. Heat can cause many health problems, from a rash to heat stroke. So what steps can be taken to prevent workers from suffering illness in hot temperatures? And, what should supervisors be watching for?

How hot is too hot?

One of the sprinkler fitters that I worked with asked me what the highest temperature a worker can work in is. According to “TLVs and BEIs” from the ACGIH, the goal is to maintain a core body temperature of 37° C. There are many factors that can affect how well the human body can maintain this core temperature. Heat stress and heat strain need to be examined to determine the risk a heat exposure.

Heat stress is “the net load to which a worker may be exposed from combined contributions of metabolic heat; environmental factors (i.e. air temperature, humidity, air movement and radiant heat) and clothing requirements”. (TLVs and BEI’s, ACGIH, 2013). Heat strain is the “overall physiological response resulting from heat strain”.

By keeping in mind the factors for heat stress, employers can begin to implement a plan to prevent workers from suffering from the heat and being put at risk of heat related illnesses.

Keeping Body Temperature Regulated

Metabolic heat refers to heat created by physical exertion. There are four categories of work as defined by ACGIH:

Light- Sitting with light manual work with hands or hands and arms. Standing with some light arm work

Moderate- Sustained moderate hand and arm work, moderate arm and leg work, moderate arm and trunk work, or light pushing and pulling. Normal walking

Heavy-  Intense arm and trunk work, carrying, shoveling, manual sawing; pushing and pulling heavy loads; and walking at a fast pace.

Very Heavy- Very intense activity at fast to maximum pace.

It is hard to regulate the intensity of work required or the air temperature and humidity, but we can control other aspects that affect heat strain. Clothing can help control the body temperature. We can now buy clothing that helps aid the evaporation of sweat from the skin. Avoid wearing clothing that is water vapor impermeable and thermally insulated in hot weather. These can add to the heat stress on the body.

Fans can be used to keep the air moving on indoor construction sites where there is no wind. The movement of air provides relief.

Taking breaks and drinking water or something similar (such as Gatorade) can also help alleviate heat strain. By allowing the body to recover the water and salt that was lost from work, dehydration can be prevented and the worker’s metabolic rate can return to normal. Frequent breaks, occurring every twenty minutes in either extremely hot weather or for workers doing heavy work, should be planned and potable water should be provided. Avoid coffee and soft drinks as these can dehydrate.


Hot temperatures can occur in certain workplaces, such and power plants and manufacturing facilities regardless of the temperature outside. An effective plan to manage heat stress must be in place to ensure that workers exposed to these temperatures are able to cope. Workers can become acclimatized to these hot temperatures after four to seven days, but a sudden heat wave can affect this. Workers should be monitored for signs of heat strain and treated to prevent it from becoming heat stroke, which is what a heat stress management program is meant to prevent.


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