In Reply to: More nitrox/air dual use: The PSI standards posted by Ken Kurtis on August 26, 2005 at 11:42:40:

I didn't advocate dual use of tanks and I challenge you to quote me. I personally avoid pumping regular grade E air into any of my tanks, or what PSI calls "normal" compressed air. However...

Any shop that partial pressure blends nitrox serves cleaner modified grade E air, or what ANDI calls Safe Air grade. It is grade E air that went through further filtration to remove any trace of combustible junk so it can be used to blend with pure O2. This air can be used on any O2 clean tank by default, and there is no reason this air cannot be used on tanks that might have been contaminated by regular grade E air. All fill whips should have check valves so there is no reason to worry about clean storage banks getting contaminated by regular grade E air that might be present in a tank.

Shops without nitrox only serve regular grade E air. Even if you don't dive on nitrox, cleaner O2 compatible air is the way to go. Shops that blend nitrox are capable of handling both O2 clean tanks and non-O2 clean tanks. Shops without nitrox lack that sort of versatility by default.

If a shop didn't blend nitrox but pumped modified grade E air, they wouldn't have to worry about pumping their air into nitrox tanks.

So... which air would you rather breathe... regular grade E or modified grade E? not that regular grade E is known to be harmful to your health.