A firefighter needs to evaporate about 1 liter of sweat per hour to be able to regulate the body temperature when exposed to extreme heat.
The human body is designed to function within a very specific temperature range between 36.5 and 37.5 Celsius.
However, fighting fires test these limits and can increase a firefighter’s body temperature to over 38 degrees.
Selection Of PPE
While there are many factors to consider to reduce the impact of heat stress on firefighters – such as hydration and heat acclimatization – a major component of heat stress control is the selection of Personal Protective Equipment (PPE).
Here, Reece Buchner, technical sales manager at FlamePro, a British specialist manufacturer of life-saving garments for firefighters, explains what to look for when specifying PPE, to reduce heat stress while fighting fires.
Insulation – Friend Or Foe
Insulation is an important part of any firefighter kit, as it keeps the extreme heat away from the wearer, however, it also keeps the body heat in.
People are aware that sweating is the best way for one's bodies to regulate the temperature, however for sweating to be effective, the air should be dry and moving, like when it’s windy.
When it’s humid, there is less capacity within the air for vapor to leave the body and that makes sweating less effective. An enclosed and insulated fire suit without airflow may therefore not promote the ideal perspiration environment.
Moisture barrier regulates body heat as it allows as much moisture vapor out as possible Moisture barriers play a crucial role in reducing the chance of heat stress. A moisture barrier is a type of material that lets vapor through and in some cases liquid (unidirectionally), making a suit breathable.
When it comes to fire suits, this moisture barrier plays an important role in regulating body heat as it allows as much moisture vapor out as possible.
Types of Barriers
There are three types of moisture barrier product technology used in firefighters’ protective garments: microporous, monolithic, or bi-component.
Each of these barrier technologies has a different level of effectiveness:
- A microporous membrane contains small passages or holes, which allows for air permeability and offers water vapor transfer by air-diffusion.
- A monolithic membrane is a continuous polymer layer without any passages (holes), and, therefore, does not have any air permeability. However, breathable monolithic moisture barriers use hydrophilic polymers which allow water vapor transfer through molecular diffusion instead.
- A bi-component moisture barrier product uses a combination of microporous and monolithic technologies and allows no air permeability.
It’s important that fire suits are designed to be wearer friendly, whilst providing optimum protection. When selecting PPE consider how easy the suits are to move in, and bear in mind the different requirements of the team depending on the job at hand.
PPE that is designed to provide increased mobility helps to reduce muscular strain, improves air circulation, and in turn heat stress.
While there is no one-size-fits-all approach to reducing the risk of heat stress amongst the fire brigade, these are all important factors to consider to ensure the team’s PPE is working to minimize the danger.