Just that.

Thats a term used in the fire service. I "breathe air" 3 to 4 times a year. Scott 4500 lb. (PSI) bottle goes pretty quick when you're working a fire or hazmat scene. I frost up the regulator pretty easily LOL.

Used to do that usually a time or three a week with the local fire department.

Just did an "air consumption" test last night. Made it 20 minutes until the vibralert went off. 3900 psi in bottle when I started. 37 minutes totally out of air and I was wringing wet.

If you're gonna breathe air, best to make sure it's certified grade D breathing air.

Don't ask me how I know.

I cannot recall how long I could last. It was not that long but I don't do well in heat. Sweat like a pig and its way worse in gear and a fire and I take a lot of air. Nope I'm not a 20 year old anymore. LOL

Seemed that I ran dry once in a structure fire around the 25 minute mark. And I never heard or felt the alerts. Then we changed to masks where you can see the level by light indicators.

I can say with certainty that you don’t want to run out of air at 90’.