Question
Will a regular organic respirator filter out isocyanates? As long as you keep the cartridges changed, will it be sufficient? As far as Air Supplied systems, is there anything that works but is cheaper that $500?

Forum Responses
Yes, it will. The reason OSHA wants fresh air feed masks is because you cannot smell isocyanates, thus you can’t tell when mask cartridges are no good anymore. One nice thing about isocyanate cured products is that the free isocyanate is mostly all gone when the product has become dust/tack free.

Bob Niemeyer, forum technical advisor

I have been sensitized by isocyanates--trust me when I say that not any cartridge mask will do. My suggestion is to pony up the bucks for a fresh air system. The iso stays in your kidneys for a lifetime. You cannot excrete it out. For five or six hundred bucks you will be in much better shape. Remember, the intake has to be mounted away from the spray area.

Think of isocyanate molecules in the air from the spraying process as Pac-man gobbling up molecules of moisture in the air and on your body. Isocyanate molecules are equally attracted to the moisture in your eyeballs as they are to moisture around your mouth, nose, and ears. Thus the full mask, gloved hands and suit or long sleeve clothing is proper spray attire.

OSHA regulations require that the painter use a fresh air system when in the presence of iso, and requires that the air be monitored for Grade "D" air. OSHA 29CFR 1910.134(d)(1).

Many of the oil-less compressor and fresh air systems on the market do not provide the monitor part. As Bob Niemeyer stated, isocyanates are odorless.

Isocyanate molecules are not filtered out as much as they are kept away from entry into the body by positive air pressure at points of entry into the body. Tyvek suits are much better than normal clothing to block isocyanates from the rest of the body.

Use a full face or hood system with a monitor--this protects the painter from isocyanates and many other gases. Why would you not want a monitor that checks for the presence of isocyanates and 32 other gases and vapors that can exist in a finishing department?

Fresh air systems with monitors using your shop air can be sized and configured to also deliver dry clean air for your spray gun.

The reason many isocyanate painters wear suits is because many urethanes are very sticky and ruin clothes, stick to skin and put highlights in your hair. Let’s also remember that many urethanes were used in closed areas such as tanks, ect.

I have sprayed isocyanate products with a monitor on my body in a spray booth and my limits were a hundred fold below any OSHA limits. Why doesn’t OSHA take the same stance on formaldehydes in conversion coatings? Germany has banned formaldehydes and uses isocyanates in place of them and over the years has seen no increase or ill effects to the work place due to them. Many companies are using very pure isocyanates, and the free isocyanates that are emitted is way below the OSHA limits. We all know OSHA gets a little carried away at times and then gets some government lobbyist group involved and you have a nightmare for the coatings companies.

I am all for personal safety. Do what you feel is best for you. I have read many reports from the US and Europe about isocyanates and I would rather spray 2k urethanes with an isocyanate catalyst before using a conversion varnish that pumps out loads of formaldehyde.

Bob Niemeyer, forum technical advisor

Have you reviewed the related Knowledge Base areas below?

KnowledgeBase: Finishing: General Wood Finishing

KnowledgeBase: Dust Collection, Safety, Plant Management: Safety Equipment

KnowledgeBase: Dust Collection, Safety, Plant Management: Hazard Communication

KnowledgeBase: Knowledge Base



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