Brake line for air

Would it be feasible to use steel brake line to plumb an air system?
Would a water trap before and after the tank be good enough to keep out enough moisture so the lines wouldn't rust from the inside out?

personally id use aluminum instead but should be fine

I used steel brake line for mine with no problems

i have used and seen stainless line,never brake line tho.

anyone else?

Ive only seen stainless and copper, id be worried about the moisture issue with regular steel brake line.

You should be alright with the brake line for air I would imagine, providing you keep up on your system maint. of course. Your typical steel air tank would most likely have more raw steel surface area inside  than a typical line job would all added up. A good water trap will obvisly be an easential piece of the puzzle as I'm sure you are aware. The only thing I'm unsure of is what the DOT thinks on the subject,  I'm sure a copy of your state/provinces vehicle code book will answer that question for you.