When approaching a ventilation-limited compartment fire, the fuel will continue to pyrolyze and will

• A. Fill the compartment with pure oxygen.
• B. Fill the compartment with fuel-rich smoke.
• C. Cause the windows and doors within the compartment to fail.
• D. Cause any void spaces around the compartment to fill with flame.

Answer: (B)

In a ventilation-limited fire, there isn’t enough oxygen to burn all the fuel efficiently. The heat continues to cause the remaining fuels to undergo pyrolysis, releasing flammable gases. Since oxygen is scarce, those gases don’t burn fully and instead accumulate as smoke that is rich in fuel vapors. That’s why the compartment fills with fuel-rich smoke. The other ideas don’t fit this scenario: adding pure oxygen isn’t what happens inside a ventilation-limited space, and while heat can affect windows or doors or cause flames to spread into voids under some conditions, the defining behavior here is the buildup of fuel-rich smoke from ongoing pyrolysis.