Air Consumption for Fire Ground Survival

Basic physiology tells us that different firefighters will consume the air in their S.C.B.A. at different rates. The working air supply will depend on the firefighter's training, physical condition, activity, and mental state experienced under the...


Basic physiology tells us that different firefighters will consume the air in their S.C.B.A. at different rates. The working air supply will depend on the firefighter's training, physical condition, activity, and mental state experienced under the stressful conditions encountered during firefighting.

A question that every firefighter should be able to answer without hesitation is, "How long can they work while wearing an S.C.B.A.?" The fireground is not the place to figure out that answer.

Basic physiology tells us that different firefighters will consume the air in their S.C.B.A. at different rates. The working air supply will depend on the firefighter's training, physical condition, activity, and mental state experienced under the stressful conditions encountered during firefighting.

Each firefighter is responsible for determining their individual point of no return whenever they enter a hazardous atmosphere. In most residential fires, the low pressure warning device is adequate to signal a firefighter's point of no return because a firefighter should be able to exit a single family structure easily after the alarm sounds. However, in larger structures, a firefighter may need more time to exit than would be allowed if the firefighter relied solely on their low pressure warning device. It is very important that a firefighter not rely solely on the low pressure warning device of their S.C.B.A. Thinking in very simple terms, the low pressure warning device activates when the air supply reaches a level of 25 % of the cylinder's capacity. This means that it took 75% of the cylinder's capacity to get to the point that the firefighter is at, which can leave the firefighter with a deficit of as much as 50% of the cylinder's capacity to safely exit. The 2002 edition of NFPA 1981 mandated the use of the heads up display (HUD) which is a visual signal signifying the amount of an air cylinder's rated capacity present. These parameters basically stated that S.C.B.A. were to have LED lights visible inside of the facepiece indicating 50% of the air cylinder's capacity remaining. Unfortunately, as we know, not all fire departments are operating with S.C.B.A. that are compliant with the latest edition of standards such as NFPA 1981.

A simple method for determining a point of no return is to check the pressure gauge before entering a contaminated atmosphere and again on arrival at the objective. The amount of air used to reach this point is the minimum amount needed to get back to a non-hazardous atmosphere.

Calculating a consumption rate from a consumption test is another way to figure an individuals point of "no return". It has advantages because a firefighter is working at a constant rate when determining it.

Consumption testing will involve a firefighter working on an obstacle course while experimenting with different breathing rates and techniques. To get a true indication, the obstacle course will need to be set up exactly the same each time a consumption test is performed.

The test should be performed until the firefighter can not draw any additional air from their S.C.B.A. This will give the individual a true indication of exactly how much time they have left to operate in the event that they become trapped or lost. It will also demonstrate to the firefighter how much air is still left in an S.C.B.A. even after the low pressure/ 25-percent alarm stops operating. Knowing this information can help keep a firefighter calm and possibly enable them to save their own lives.

There are various methods of breathing that may help in reducing a firefighter's consumption rate. It will take experimentation on the firefighter's part to find which one works the best for them. When using any method, it is important to take normal breaths and exhale slowly to keep carbon dioxide (CO2) in the lungs within proper balance. Firefighters also should never hold their breath in an attempt to save air. Due to the body's release of adrenaline when firefighting, oxygen is being consumed at a higher rate and holding the breath could cause unconsciousness.

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