They detect the first signs of smoke, which rises to the top of the room. Firefighters know this and that is why, when they enter a burning building, they are down on their hands and knees. There is far less smoke near the floor and the visibility is much better. In most cases, fire fatalities result from victims who have succumbed to smoke inhalation long before burn injuries occur. Eighty percent of those who die in residential fires have first inhaled smoke and other toxic gases.
Fire produces many gases that are highly poisonous.
These are found in smoke and include carbon monoxide, sulfur dioxide, hydrogen cyanide and hydrogen sulfide. They displace oxygen in the room, which can cause suffocation. Fire also consumes oxygen. This reduces the amount of oxygen available for persons to breathe. When a person is exposed to the toxins of smoke, muscle control is lost, judgment is impaired and the ability to reason diminishes.