OK spd, so knowing what you know, if you're putting together a hookah or snuba rig, would you use cheapo industrial air hose?
For shallow diving I, personally have 2 set ups:
1. A 30' hose manufactured for scuba set up with a first stage. This hose was $100.00
2. A 100' goodyear hose that I have set up for a first stage for shallow (40' or less) diving with more reach. I spliced a scuba hose to each end (First stage portion on one end, and regulator fitting on the other). This hose was $30.00 and works well.
With either set up, I use a bailout bottle with scuba if I am deeper than I can just stand up. If I am rigging bags on a car or boat in shallow water I may use a hose only. If entanglement or water over my head is a real issue, I use a bailout too. If I was diving for lobster and such, with no one on the top to yank my hose if there was a problem, I would also carry sufficient bailout to ascend, stop, and surface when a safe stop has been done.
The bottom line is real common sense. It is obvious that each atm we descend the partial pressure of what is in our breathing medium, or picked up from the hose, increases. Any trash gas that can occur through a breathing hose (chemical reaction?) has to be considered. This can be a clear danger.
The real experience I have found though is breathing "air" 40' or above has not presented any real health issues over the last 10 years or so of using them from time to time. For what the OP is wanting to do, it is probably safe, but that is for the OP to consider, especially after the information that has been presented here.