Taking the Heat
What happens after a worker experiences a heat-related illness?
Most guidelines suggest that workers can easily relapse within a week after suffering heat illness, but new research indicates that their susceptibility may last far longer. “Heat intolerance” has been most closely studied in the armed forces because soldiers who collapse under conditions of high heat and heavy exertion and return to duty too soon tend to suffer secondary collapses.
Many factors can affect a worker’s underlying heat tolerance, examples:
Air temperature and humidity
Direct sun exposure
Indoor radiant heat sources (ovens, hot manufacturing processes, etc.)
Limited air movement
Not drinking enough fluids (dehydration)
Personal Protective Equipment (PPE) or clothing
Lack of recent exposure (not acclimatized)
Advanced age (65+)
Once a worker has suffered a heat illness, the illness itself becomes a predisposing condition that can indicate an increased susceptibility to heat illness.
Workers who have suffered heat illness should not return to work right away. Determining when a worker can return to working in the heat, after suffering a heat-related illness is affected by the following factors:
Preexisting susceptibility - Some people are naturally heat intolerant, but this is not usually discovered until after they suffer a heat-related illness. These workers will remain intolerant to heat; acclimatization will not help them.
Recovery time - Some workers develop temporary intolerance to heat after suffering a heat-related illness. They may remain heat intolerant for several months. A heat tolerance test in which the individual walks on a treadmill in a climactic chamber while being closely monitored can determine whether they can safely return to work.
One factor that doesn’t seem to affect a person’s heat tolerance, following heat illness, is the individual’s overall physical fitness. Overall, fitness has no effect on whether a person becomes heat intolerant after suffering a heat-related illness, so don’t use that as a return-to-duty criterion.