The Role of Heat in 

Workplace Incidents 
The Role of Heat in 

Workplace Incidents 

Whether they’re working under the searing sun or near 

processes and machinery that are blasting heat, some 

roles expose workers to extreme temperatures. 

Safety professionals need to understand how heat 

contributes to unsafe conditions and what to do about it 

on their sites. By anticipating heat as an environmental 

risk factor, we can establish more effective controls 

and help prevent incidents. 
Heat and Workplace Incidents 

When we investigate an incident, our goal is to establish a cause deeper than placing 

fault on an individual. Reporting that an incident occurred because “Joe wasn’t paying 

attention” misses the point and it doesn’t provide us with any actionable information. 

An investigation needs to turn up systemic problems that suggest corrective action. 

If Joe wasn’t paying attention, we need to identify the reason he wasn’t. 

Could it be the heat? 

Inattention is never the root cause – we always need something to explain the 

inattention. It could be tiredness due to an exhausting schedule, distraction by 

attempting to multitask, or working in extreme heat for too long. 

Heat stress has both cognitive and physical effects, and they can directly affect how a 

worker performs their tasks. 

The list of symptoms include: 

• Confusion 

• Dizziness 

• Fainting 

• Muscle weakness 

• Cramps 

Any of these could contribute to an incident. So, Joe is off the hook – it’s the heat we 

need to address. 
Controlling for Heat Hazards 

Heat is not a subtle or unpredictable variable in most cases. That means it has to 

be controlled. 

Applying proper controls requires some understanding of heat’s effect on a worker. 

The body’s main mechanism for getting rid of excess heat is radiation, which happens 

passively across a gradient. If the surrounding temperature is higher than the body 

temperature of 98.6oF, the radiative mechanism won’t work and actually reverses. In 

other words, the body will take in heat instead of releasing it. 

In an environment hotter than body temperature, sweating is the only defense 

mechanism the body has left, and it can only work if the sweat can make contact 

with the air and evaporate. 

Clothing can prevent that from happening effectively, and the heavier the clothing, the 

greater the effect. 

Wearing fewer layers isn’t always an option, though. A lot of the really hot jobs also 

happen to be the ones that require heavy PPE. Think of the work done in a foundry. The 

ambient heat from molten metal and heavy machinery easily reaches hazardous levels. 
 

The heavy gloves, coveralls, and hoods needed to protect workers from sparks, slags, 

and other hazards directly increases the risk posed to them by the heat. 

Ultimately, heat-related illness mainly results from dehydration. The body sweats, 

loses water and electrolytes (salts) in an attempt to cool itself when it’s hot. Those 

lost fluids need to be steadily replaced to avoid negative impacts, ideally with an 

electrolyte beverage. 

3 to 4% 2% 

Most healthy people can tolerate 3 to 4% body water loss before displaying significant 

symptoms, but it only takes 2% dehydration for mental functions to become 

substantially impaired. A worker’s reaction time, attention, and multitasking capability 

simply become less reliable when they’re overheated. In these cases, heat stress’ 

contribution to an incident may masquerade as inattention or distraction. 

Most healthy people 

can tolerate 3 to 4% 

body water loss before 

displaying significant 

symptoms 

But it only takes 2% 

dehydration for mental 

functions to become 

substantially impaired 
Controlling for Heat Hazards 

So, what can we do to mitigate the risk that heat contributes? 

Engineering Controls 

Engineering controls such as improved ventilation can help facilitate the body’s natural 

cooling mechanism. Moving air is far better than stagnant air for allowing the body to 

radiate heat by constantly removing and replacing the air layer around the body. The 

same mechanism facilitates the evaporation of sweat. 

When ventilation isn’t practical or doesn’t do the trick, a cooling vest might be useful. 

Cooling vests are either designed to hold freezer packs or circulate water around the 

body. If the ambient environmental temperature can’t be altered, a product like this 

might help reduce the effects of heat stress. 

Administrative Controls 

We can also apply some administrative controls. 

One control for a specific scenario is scheduling acclimatization periods for new 

workers. Over time (and to a point), an individual can acclimate to working in a hot 

environment so that the body gradually gets used to it. 
New workers should be phased into a schedule with less time between breaks for the 

first few weeks working in a hot environment. Special care should be taken to ensure 

that heat stress doesn’t combine with the already-high incident potential that new 

workers face. Being new to a role means they are already three times more likely to get 

injured during that first month on the job. The impaired faculties caused by heat stress 

can multiply the probability. 

Special consideration should also be given to fitness for work when heat is a factor. 

Those with high blood pressure or other cardiac conditions are at additional risk of 

serious consequences when the heat is on. 

For the acclimated worker, ongoing administrative controls could include frequent 

breaks and awareness of dehydration. 

The latter is a key strategy. In the confusion of heat stress, a worker may not recognize 

the warning signs in themselves, but a co-worker may spot them before a serious 

situation develops – provided they know what to look for. Heat exhaustion produces 

some telltale symptoms such as heavy sweating, paleness, cramps, and dizziness. 

Catching it at an early stage provides an opportunity to handle the situation and reduce 

the impact. The worker can take a break in a cool place, drink water or an electrolyte 

drink, and remove excess clothing to beat the heat. 

Always Factor in the Heat 

Heat is one hazard that can rarely be eliminated. Outdoor work can’t be taken indoors 

just because it’s hot, and heavy machinery and hot work processes are always going to 

raise the temperature. 

But heat is often very predictable. So, be sure to factor it in your planning, your safety 

program, and implement the control methods needed to keep workers safe. 

Check out our Heat Stress Knowledge Center for more content.