Preventing Heat Stress While Wearing Personal Protective Equipment

During severe disease outbreaks such as the 2014 Ebola virus epidemic in West Africa, wearing special gear can protect healthcare workers from exposure. This personal protective equipment covers the face and body to provide a physical barrier against germs. In addition, a respirator prevents the inhalation of airborne germs.

Since many types of personal protective equipment worn during the Ebola response are made of heavy, fluid-resistant material, which can prevent sweat from evaporating and cooling the body, heat stress is a concern in hot weather.

At NIOSH, the safe use of personal protective equipment is a priority. Two studies recently published in the journal Disaster Medicine and Public Health Preparedness focused specifically on preventing heat stress while wearing this equipment in hot, humid environments.

Volunteer study participants included six healthy, young men who received medical clearance by a licensed physician. To simulate working in the hot and humid conditions of West Africa, participants walked on a treadmill for 60 minutes in a special environmental chamber set to 90 degrees F (32 degrees C) and 92% relative humidity.

After comparing three commonly used ensembles, NIOSH investigators found that different types of personal protective equipment were linked to increases in heart rate and body temperature during exertion.

The first ensemble tested included a face shield and a fluid-resistant surgical gown. The other, more elaborate, ensembles included goggles, coveralls, and a separate hood for the second one, and highly fluid-resistant coveralls, a separate hood, and a surgical mask cover over a NIOSH approved N95 respirator for the third one. Participants wore each of the ensembles over standard medical scrubs.

Compared to participants wearing the first ensemble, those wearing the second and third ensembles had significantly higher heart rates and body temperatures after exercising on the treadmill. In addition, participants wearing the second and third ensembles reported feeling hotter and more tired. These findings underscore the importance of training healthcare workers and regulating agencies in the proper selection of personal protective equipment to prevent heat stress.

In addition to training, it is important to balance work in hot conditions with adequate rest periods and to use heat-prevention strategies such as cooling vests.