After reading about limited air drills some time ago I set out to try one this evening at the end of my workout. I set up the “500 PSI drill” by draining my SCBA cylinder via the purge valve to exactly 500 PSI (according to the digital readout anyway) and setting up a few workout stations while waiting for the cylinder and SCBA to return to room temperature. The workout stations are intended to increase your heart & breathing rate to something that you might find on the fireground. We use a 4500 PSI cylinder where I work but this could be done with any pressure cylinder.
The purpose of this drill is to reinforce the importance of calling a mayday sooner rather than later, provide a hands-on reference for the usefulness of the last 500 PSI and emphasize how critical it is to be working with a full cylinder. Performing it only once may not provide any hard & fast metrics for its applicability to the fireground so you may want to re-run the drill a few times to get a better sense of time that the last 500 PSI provides.
For workout stations I used a kettle ball for squat/swings, 15kg plate for lifting over the head, a spot for pushups and the tailboard of the engine for steps. I worked out to the point of moderate-to-hard physical exertion during this drill but it might be useful to re-run it just sitting in a corner and controlling breathing, too.
I also modified the SCBA by placing some ear plugs in between the warning whistle and discharge hose so as to disrupt the whistle but not stop the flow of air through it. Our SCBA also have an electronic low-air alarm that I disabled by removing the battery. I don’t believe that the low-air alarms are particularly pertinent for this drill - maybe they have some added psychological effect but I was doing this drill in the apparatus bay and didn’t want to drive myself or others mad with the noise.
Put on the SCBA & face piece, turn on the cylinder and start a timer. I went 00:04:30 before the face piece started to stick to my face and 00:04:40 by the time there wasn’t enough air to draw sufficient volume.
This is a useful drill that requires a minimum of time to setup. Give it a try. What is your experience?
If you are looking for formal drill sheet for this kind of thing check out 500 PSI Drill.pdf from Fire Engineering.