Having just read "Air Management in the Fire Service" by the guys from Seattle Fire, I'm curious about what other depts are doing to deal with NFPA 1404 and the Rules of Air Management proposed by the book. Are depts changing their practices about leaving IDLH atmospheres during fires before their low air bells are activated?
Just think of how much time it takes you to get to where you need to go inside an IDLH atmosphere, it will take you at least just as long to get out. If you wait until your low air alarms start sounding, well... it may be too late.
We use the Rule of Thirds just as SCUBA divers do - 1/3 of your air to enter and work, 1/3 to exit, and 1/3 to get out.
We have 4500 PSI, 45-minute SCBAs. We do frequent air guage checks and when the first member of a company or crew hits 3000 PSI, the crew exits, particularly in big box or high rise fires where the company is not near an exit.
If you wait until your low-air alarm rings in a Home Depot or Wal-Mart, call the Maydayright now, because you probably don't have enough air to get out, even if you're following a hose line to a door.
See the NFPA 1407 Standard on Training for Fire Service Rapid Intervention Teams for more on this topic.
While it is policy, I'm not going to pretend that it happens every time. Most of our people have learned to watch the HUD, and are leaving before the low air alarm sounds. But there are occasions where we haven't been as observant as we should be, (and I include myself).
We likewise have a 2 bottle maximum, and then to rehab.
Big box x low air alarm = death! The old adage that you have a least five minutes is not the case! The pressure that's left in your bottle along with your breathing rate, cant tell time. Get out before the alarm, so you can go home!!
We, as most of the posters here, also try to stay on top of our air supply and really do make a habit of being out prior to the low air alarm. It doesn't always work but we try. 2 in 2 out is strictly enforced. One of the little things that we incorporated several years ago is that our dispatch (PD in our case) gives a quick heads up every 15 minutes that we have been on scene. eg; "PD to XYZ street command you are on scene for 15 mins", then at the 30 min mark they advise "PD to XYZ street command you are on scene for 30 minutes" and so on. This has worked great to help all of us (we all have radio communications) not loose track of how long we've been working and to remind IC that they need to be checking air status of working crews so they can be rotated. With us using 45 minute bottles this has been very helpful with the rule of thirds that Chief Waller commented on. We also use the Grace Pass system and we strictly enforce activating your device when you come out of the rig no matter if you are assigned to interior or outside functions.