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Candidate is able to identify and explain all layers of a firefighter's PPE.
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What are the three PPE layers? (Outermost to Innermost)
Outer Shell or Outer Layer
Moisture Barrier
Thermal Barrier
Outer Shell or Outer Layer
Outermost Layer
Sturdy: Resist abrasions
Waterproof
Flame resistant material (Nomex, Kevlar, or PBI- Polybenzimidazole)
Fluorescent reflective material provides visibility in smoke conditions and at night
Moisture Barrier
Middle Layer
Flexible membrane, attached to the thermal layer. Works to ensure the thermal layer does not absorb water, as water absorption in high temperature environments can cause super heated liquid/steam burns.
Prevents the transfer of water, steam, liquid chemicals (combustible liquids), vapors, any liquid contaminants to skin.
Allows for vapor transmission to prevent overheating. The porous film allows water vapour molecules/sweat to escape but is small enough to prevent moisture from entering (i.e, why it is also called the “vapor barrier”).
Thermal Barrier/Liner
Innermost Layer
Multilayered, quilted material that insulates the body from external temperatures. Works with the other layers by trapping layers of ‘air’ (via tiny pockets in the liners of the bunker gear) to prevent heat conduction.
Enables the firefighter to operate in elevated temperatures and keeps the body warm during winter.
How does structural firefighting PPE work to protect you? How much can it protect you from?
It can only protect you under limited conditions.
On their own,
the outer layer defends primarily against external environmental conditions (water, physical objects)
the moisture barrier protects against liquids & vapors while allowing moisture regulation (sweat) via vapor transmission
the thermal barrier protects against external temperatures
Together: They work like a sponge to absorb heat from elevated temperatures. After a certain period, in a high temperature, the heat transfer will increase as the PPE’s capacity to ‘absorb’ the heat decreases. (Think like a sponge absorbing water).
Watch this video for a brief explanation: