What method of fire extinguishment is referred to as "suffocation"?

The method of fire extinguishment referred to as "suffocation" is based on the principle of reducing the oxygen available to the fire. Fires require oxygen to sustain combustion, typically in the form of atmospheric air which contains about 21% oxygen. By diluting this oxygen concentration or entirely displacing it with an inert substance—such as carbon dioxide or a fire suppressant—fire cannot continue to burn.

This approach effectively "suffocates" the flames by preventing the chemical reaction necessary for a fire to persist. In environments where this method is applied, the oxygen levels are lowered to a point where the fire extinguishes itself due to an inability to maintain combustion without sufficient oxygen. Techniques employing this principle include using foam, gases, or certain chemicals that displace or limit the air’s oxygen content.