Suck the exhaust pipe, or not?

[weirdwilbur]

My 1-gallon ShopVac, Cyclone and 5-gallon bucket have been mounted on their own hand truck.
Now I want to capture all of the exhaust, and direct it into a ShopVac 6" HEPA filter. The HEPA exhaust will then be directed, by flexible tubing, to a sealed Space Shuttle helmet. I shall stuff my head into this helmet with the intention of breathing the, possibly clean, HEPA air.
The idea of breathing exhaust of any kind gives me the creeps, but logic implies that this might work. I would be grateful for any opinion regarding the efficacy of the concept. I tried asking my friends but they just roll their eyes.
The purpose of this is to breath clean air without constantly fumbling with a mask and safety glasses.

 

[McRabbet]

That is an adventuresome concept, but I doubt it is very practical. Even a small ShopVac will put out much more air than needed for breathing and it is warmed by the unit, yielding hot air. I'd suggest a more proven method, while fairly expensive, is well-engineered and provides a cool, very well filtered airflow unencumbered by a hose. It is the Trend Air/Pro Airshield full faceshield, detailed here. It offers excellent protection for woodworkers in dusty environments.

 

[weirdwilbur]

Suck the exhaust pipe, or not?

Thank you very much for your time and advice. In the interest of economy I elected to whine only about the issue with which I needed the benefit of someone with wider experience than my own.
All other considerations having been addressed to my satisfaction, the final consideration, before I take the pipe, is the air quality within the pipe. Will it be as clean as the driven snow? Hmm. Okay, bad example. Will a new ShopVac HEPA filter actually put out air that is safe to breathe for extended periods, given that the air runs first through a cyclone, and then through the filter in a 1-gallon vacuum cleaner before it finally reaches the 6" HEPA filter. Assuming that the hoses are clean, will this air be clean enough to breathe?

 

[bababrown]

I have a Rigid vac with the CV lid that Ed Morgano made for a short time (the one that looks like a toilet). I replaced the filter with a Clean Stream hepa filter. I can vacuum up sawdust right in front of my particle counter and the numbers barely increase. So I think the air is safe. McRabbet is correct in that the airflow is way too high. I have the early Trend helmet and that supplies about 6 or 8 CFM whereas a shop vac supplies 130 CFM or so. If you try the idea you might bleed some of the exhaust air into a much smaller lightweight hose to the helmet. You could use a 2-1/2 inch Y fitting with the branch necked down to the smaller hose. Good luck!
bababrown