By Brice Long, MTI Fellow
During normal firefighting operations, the capacity to extend an air cylinder can allow a company to stay inside for longer, accomplish more work, and save the embarrassment of being relieved by another crew too quickly. Under emergency circumstances, making the most of a bottle can be the difference between life and death.
In this study, we’ll assess several techniques with the intention of identifying an effective and practical method of slowing the consumption of a self-contained breathing apparatus (SCBA) air cylinder.
Modern firefighting SCBA work really well. The harnesses are comfortable and secure, the facepieces seal like glue to the user’s face, and the air cylinders are lightweight and durable. Yet even the most advanced systems still can only carry a finite amount of breathing air for the user.
For this study, we’ll use the Scott Airpack 75 with 4500psi air cylinders. The 4500psi SCBA cylinder contains 1,840 liters (66 cu. ft) of breathing air and is stamped “45-minutes” on the side (1). This is the manufacturer’s rating, not the fire department’s. Under working conditions firefighters should expect their cylinders to empty far sooner than the number on the side would lead them to believe. There are of course many factors that contribute to the length of time a firefighter takes to expend a full cylinder: size of the person, fitness level, stress level, work intensity, etc. However, it’s a safe bet that if a firefighter is wearing a 45-minute SCBA at a fire it will not last 45 minutes.
In basic training, firefighters are taught the rules of air management (ROAM) or some similar variation for safely working with a limited air supply.(2) ROAM dictates that 25% of the cylinder can be used to get to the fire, 25% can be used to work there, 25% is for getting back out, and the remaining 25% is a reserve in case something goes wrong.(3) In theory this sounds easy enough, but in practice it’s not so cut and dry. The amount of air a firefighter consumes when fresh and making his or her way into a structure is likely going to be less that the amount he or she will require to get out if something bad happens. When stress kicks in, the body naturally elevates respiration rate and in turn firefighters consume more air. For this reason we need to identify the best method for conserving air – especially in the worst situations.
The best way to save air is of course to do as little as possible. Sit down, stay still, and breathe as slowly as one is able. Utilizing this tactic, a full cylinder can last hours – but this is not real life. Firefighters need a way to continue to work, to continue to search, and continue to make their way out of a bad spot while conserving their air supply as best as they are able.
The Mission Direct Study
We’re chasing a couple key questions here:
- (1) Which technique works the best? Based on the results of the test, which one makes the cylinder last the longest?
- (2) Which technique is sustainable? The best one might be tough to do, which could make it not a viable option in an emergency situation. We’re looking for the most effective technique that we can actually recommend to firefighters.
Six full-time firefighters, five males and one female, will take part in the study one morning after a 24-hour shift and our plan is to accomplish all the testing in one day. Each effort should take 7-12 minutes and we’ll space them out with adequate time for a full recovery – at least a 1:2 work to rest ratio.
The athletes’ heart rates will be monitored during the test and we expect that the best breathing technique will also produce the lowest relative HR for the athletes. (Relative to the RHR of each). This metric will be tracked using their average HR over the duration of each test.
We’ll be looking at four different breathing techniques for air conservation:
- (1) Skip breathing – A normal inhalation held for several seconds, followed by an additional inhalation before exhalation
- (2) Box breathing – A slow inhalation over 3-4 seconds, hold for 3-4 seconds, exhale over 3-4 seconds, and then hold for 3-4 seconds before the next inhalation
- (3) The Reilly Emergency Breathing Technique (R-EBT) – A slow inhalation followed by an exhalation controlled by the athlete making a humming sound as the breath is released
- (4) Straw breathing – A slow inhalation followed by an exhalation controlled by pursing the lips to mimic breathing through a straw
We’ll also conduct a control test without a specific technique. Participants will be instructed to try to breathe slowly and conserve air, but won’t be assigned one of the above listed procedures.
The participants will begin the test wearing PT clothing and an SCBA with 1,000psi of air. When the “go” command is given, they will attach their regulators and begin the test. It was designed with the metabolic demands of an emergency situation in mind, loosely based on a popular firefighter emergency exercise, “The Pittsburgh Drill.” (4) Set to a 30bpm metronome, the procedure is pretty simple:
- 15 step ups onto a 20” box (crawling or other slow deliberate movement)
- Turn and address a barbell
- 5x, 95/135# Deadlifts (overcoming an obstacle, moving an object, using hand tools) – 95# for women, 135# for men
- Turn back and address the box
The participants will complete this cycle until the SCBA low air alarm stops.* At this point, they will stop working and continue the breathing technique until the cylinder is completely empty.**
*Why does the low air alarm stop?
The low-air alarm (Vibralert) on Scott Airpacks is activated when the cylinder pressure reaches 20-25% of its rated capacity, so 900-1125psi. At this point, the secondary pressure regulator is activated and the mask mounted regulator is supplied with air at 145-165psi, activating the Vibralert. When the cylinder pressure drops below 145-165psi, the low air alarm will stop and the user knows that his or her cylinder pressure is now about 3%. (5)
**So why stop working when that happens?
Not long after the low air alarm stops, the user’s breathing becomes restricted by the low air pressure. It feels as though each breath is being drawn out of the regulator, rather than being supplied. Tolerance for this sensation, especially when working, is very much dependent on the individual. By ceasing the work portion of our test before this occurs, each athlete should be able to continue the technique until the entire cylinder is exhausted.
- Marino D. Air Management: Know your air-consumption rate. Fire Engineering. 2006 Oct 1 [accessed 2017 Mar 25]. http://www.fireengineering.com/articles/print/volume-159/issue-10/features/air-management-know-your-air-consumption-rate.html
- Goodson C, Murnane L, editors. Essentials of fire fighting. 5th ed. Upper Saddle River, NJ: Brady/Prentice Hall Health; 2008.
- Gagliano M. Air management for the fire service. Tulsa, OK: PennWell; 2008.
- Rapid Intervention Training Associates. The Pittsburgh Drill. Prop Shop. 2002 Feb [accessed 25ADAD Mar]. https://www.in.gov/dhs/files/pittsburgh.pdf
- Air-Pak® Self-Contained Breathing Apparatus Pressure Reducer and Low Pressure Breathing Regulator Theory of Operation. Air-Pak® Self-Contained Breathing Apparatus Pressure Reducer and Low Pressure Breathing Regulator Theory of Operation. 2000.
Brice Long is a career firefighter in northern Virginia and a Certified Strength and Conditioning Specialist (CSCS) through the National Strength and Conditioning Association. This study and analysis is his project for his MTI Fellowship.