Why should personal protective equipment be dry before engaging in structural firefighting?

Why should personal protective equipment be dry before engaging in structural firefighting?

• A. Nomex is rendered non-flame-resistant when wet and heated
• B. the outer shell becomes brittle and tears easily when wet
• C. water trapped in the fabric can cause steam burns
• D. water trapped in the fabric greatly enhances its thermal protection and that cuts off abruptly when the fabric dries

Answer: (C)

Moisture in firefighter PPE undermines its ability to protect by changing how heat moves through the layers. When the fabric is wet and then exposed to flames or high heat, the water trapped in the layers vaporizes into steam. That steam carries a large amount of energy and can transfer it rapidly to the skin, causing severe burns even if the outer materials are still burning-resistant. The latent heat of vaporization means a small amount of water can release a lot of heat as it becomes steam, so the gear loses its insulating value and becomes a pathway for heat to reach the wearer. Keeping the PPE dry preserves the air gaps and insulating barriers that slow heat transfer, reducing the risk of steam burns. The other statements about the gear’s material properties when wet aren’t accurate, and they don’t capture the principal hazard of moisture in PPE.

Moisture in firefighter PPE undermines its ability to protect by changing how heat moves through the layers. When the fabric is wet and then exposed to flames or high heat, the water trapped in the layers vaporizes into steam. That steam carries a large amount of energy and can transfer it rapidly to the skin, causing severe burns even if the outer materials are still burning-resistant. The latent heat of vaporization means a small amount of water can release a lot of heat as it becomes steam, so the gear loses its insulating value and becomes a pathway for heat to reach the wearer. Keeping the PPE dry preserves the air gaps and insulating barriers that slow heat transfer, reducing the risk of steam burns. The other statements about the gear’s material properties when wet aren’t accurate, and they don’t capture the principal hazard of moisture in PPE.