What method does steam extinguish fires by?

Steam extinguishes fires primarily through the methods of smothering and cooling. When steam is introduced into a fire scenario, it works by displacing oxygen in the vicinity of the flames, which is crucial because oxygen is one of the three essential elements needed for combustion (the fire triangle). By reducing the available oxygen, steam effectively smothers the fire, helping to suppress the flames.

Additionally, steam has a high latent heat of vaporization, meaning it can absorb a significant amount of heat when it converts from water to vapor. This process cools the surrounding area and lowers the temperature of combustibles, further aiding in extinguishing the fire. The combination of these two methods—displacement of oxygen and absorption of heat—forms an effective means of fire suppression with steam.

Other methods listed in the choices do not accurately describe how steam functions in fire suppression. For example, chain breaking refers to disrupting the chemical reactions in a fire, while absorption and displacement might relate to specific extinguishing agents rather than steam. Cooling and filtration are general terms that do not capture the specific actions steam takes in extinguishing fire.