Which gaseous system is described as being ineffective on cellulose nitrate?

• A. Clean Agent
• B. Halon
• C. CO2
• D. Inergen

Answer: (C)

Gaseous extinguishing methods work in different ways: some displace or dilute the oxygen, some cool the flame, and others chemically inhibit the flame reactions. Cellulose nitrate is a very reactive nitrocellulose-based fuel that can burn vigorously and may continue to burn even when the surrounding air is lowered in oxygen. Because of that, simply removing oxygen with CO2 often doesn’t reliably stop the flame or prevent afterglow and reflash, as the chemical reactions in nitrocellulose combustion aren’t sufficiently interrupted by oxygen deprivation alone. The other agents, such as clean agents and halons, interrupt flame chemistry or provide effective cooling, and inert gas systems like Inergen reduce the flame-supporting oxygen to suppress combustion without relying solely on displacing air. That combination makes CO2 the least effective choice for fires involving cellulose nitrate.