: The problem is there is no filter for isocyanate. The only solution for it's
: use is supplied fresh air.

: Been thru this many times. If you have to use this varnish, suggest doing a
: web search for HobbyAir. It's a fairly inexpensive supplied air
: respirator. Gonna be a heck of alot less money using a less toxic varnish.

: Bill H.

For several years I have owned the basic HobbyAir system, using it primarily for woodworking and boat building. I have never used the system for any urethanes or two part products, only for epoxy, stains and varnishes. I find it satisfying to know that I can pull air out of my back yard, which is inhabited by plant life, and feed it directly to my lungs in the garage.

Initially I used the included HobbyAir half-mask, then ordered the simple tyvek hood to protect my eyes. By mistake they sent me the direct feed hood, which is designed to provide protection without the need of a facemask. I have found the direct feed hood to be slightly inadequate when the concentration of contaminates is higher. The direct feed hood is great after products have outgassed to some degree. I have also used the direct feed hood over the supplied air half-mask, leaving the direct feed hood air intake disconnected. I could re-order the simple tyvek hood in addition, and may do that.

I have found the 40 feet of hose adequate for my needs, and I just watch to make sure I don't go in one direction around my project too many times. Occasionally need to straighten up the hose while working.

Personally, I have no intention of spraying any two-part urethanes. Having used the HobbyAir system, I would think that the full-face supplied air facemask would be necessary, along with a fit test, and all other precautions.

I also use a 3M 7503 half-mask, and a 3M 6900 full-face mask, both with 6001 filters. I wish I could hook my 6900 full-face mask up to the HobbyAir, as HobbyAir's full-face supplied air mask is expensive.

Regarding 3M 6001 filters: I have a friend who works in an industry where part of his job is to instruct workers on the proper use of organic respirators. Mike has a degree in chemistry, and a masters degree in geohydrology. I once told Mike that I was keeping my mask and filters in a zip-lock bag when not in use. He told me to not do that, as the bag keeps the concentration of contaminants in the filters. When you remove your mask and take your first breath, the contaminant concentration will be higher than if you had stored your mask in fresh clean air.

In reading the 3M site, it is significant to note that the 3M 6900 full-face mask provides a great deal more protection than a 3M 7500 half-mask.

Well anyway, these are some things that I have learned as a builder-hobbyist, and hope that this might contribute to our discussion.

Chris Sperry