more info for ya, copy/paste from garage journal dot com
I would like to add to the discussion that there is a new breed (well, not that new) of flexible plastic piping that is designed for air and is really easy to install. One brand is "RapidAir" but there are many.
This stuff is really good. Very easy to install, many use quick connect fittings so you just cut and push together. Reliable and doesn't leak. Easy to re-route. Think of it like PEX for air lines. It isn't super cheap but is a really good solution. You might want to investigate. Many companies use this stuff nowadays.
It's made from a plastic, huh? I thought it was a aluminum with ABS-type plastic fittings. I was a trade show a few years ago and saw the stuff that's rebranded by Prevost and Kaiser -- it's a blue pipe with the black plastic fittings.
Maybe RapidAir is something different.
I myself would still use black pipe, cheep, and easy to use, and because of the spark factor.