Jim,
Beleive me if you don't have to you don't want to be on supplied air. It a real pain to be tied to a tube. For boat building a combination oganic and dust filter is going to get you covered for what you need. Just make sure your dust mask is duel cartrige and approved to 3 microns.

Supplied air is good for projects like the inside of yatch hulls, ship building or in refinish shops. Most of what is done in yak building can be saved for a nice day. If your growing older and wiser in the trades, your probobly going to have to use your noggin to figure out what your up against. If your in a shop that puts you up agiandt asbestous and stripping fumes etc, it might be a wise idea, but its going to take a whole shop install to make the difference. Also you need to factor in the concept that your losing your ability to talk to your work mates and in most situations that is the bigger safety hazard. Working on hand signals round a saw is less then optimal.

For most appications in the trades any of the duel mask organic/3 microns dust cartridges will serve ya just fine. If your going on supplied air a scot pack full face duel port with a head net and 5 band adjsutable attachment, is all ya really need to know. Make sure your air pump is appoved for breathing air. Or you'll end up breathing the oil used to lube the pump.

Still spending money for safety never hurt. Beleive me health lungs is a wonderful thing. However, for most situations a good face mask that fits your face, with frequent changes in cartrdges will cover the need, keep ya mobile commmunicating and save you bucks and hassle.

As the Moodie Blue sang it....

Breath Deep....
!RUSS