> The real cheap way is to use a garden hose and suck on it. Breath in
> through the hose, and out through your nose. All by itself, this method is
> rather silly. But you can incorporate a scuba mouthpiece to make the
> breathing easier.

The important thing is to NOT exhale back into the hose. Otherwise, after a few breaths you will end up with your own carbon dioxide just going back and forth in that tube -- and you won't be getting very much, if any, fresh oxygen. As long as you just keep sucking the air FROM the tube, and exhaling elsewhere you'll be OK.

The mouthpiece from a snorkel is probably easier to come by, and cheaper. If you can find a snorkel with a purge valve, and rig up an additional one way valve in the intake line you don't have to exhale through your nose.

> The other way is to us a military surplus gas mask. This gives you eye
> protection, and the built in one way flapper valves. Rig up to your garden
> hose (or other hose of choice) and away you go.

There are two one-way valves in these, and you probably need both. They are set up to work in opposite directions. The first allows air to be sucked into the mask. That valve is forced shut by the pressure of your breath as you exhale, but the other valve opens to allow you to exhale. Many respirator masks have similar valves that allow you to breathe in through the filter, and then breathe out through an exhaust valve. You might try adding an air line to one of these.

The longer, and/or narrower, the hose that you are trying to breathe through the more you will need some pressure at the far end to force air to you.

By the way, if this is going to be such a hazardous situation to work in, I sure hope you are getting paid handsomely for your efforts!

PGJ