More information to consider, please read on: A proper cartridge on a
respirator can protect you from isocyanates (combi-cartridge type). The
problem that comes into play is that it takes a miniscule amount to, first,
cause sensitization, and second, cause an allergic reaction once sensitized.
Case in point, a typical PEL (permissible exposure limit) for an isocyanate
is 0.005 ppm. A negative pressure (not air supplied) respirator provides a
5 to 10 protection factor on the PEL, so at best case scenario, you can be
exposed to 0.05ppm (we're talking just a few molecules here) with your
respirator on. In practical terms, that means a momentary crack in the fit
between your face and the respirator results in an exposure that can lead to
sensitization. So Whitney's comments about becoming sensitized are real and
can easily occur with cartridge type respirators - the problem is usually
the fit, not the cartridge. Furthermore, you can see why he's seeking out a
positive pressure (supplied air) respirator. I've seen severe cases at
aircraft manufacturing facilities where a person who's been sensitized (and
who now has developed an allergic reaction) can't even approach the building
without having a severe asthmatic reaction. However, some folks work with
isocyanates all their lives and never develop an allergic reaction. It's
really a mystery. However this doesn't consider the effects of the volatile
exposure and other goodies in the particular brand of paint you are using.
Also consider that isocyanates cause the sensitization in their monomer
state (part A, part B). Once mixed and catalyzed, it's now a new chemical
and other factors come into play. Therefore, it's extremely important to
make sure that you always keep a cap and/or lid on everything until you're
ready to go and mix things in a well ventilated area where ventilation is
away from your face (even though you have your respirator on). To
summarize, in industrial hygiene circles, isocyanates are bad news. Please
read your MSDS carefully.
I realize this doesn't answer your original question. I just want folks to
realize what they're dealing with. My experience lies in industrial hygiene
so I can't speak to hobby safety products. I just know that industrial
supplied air respirators, once properly fitted, work pretty darn good.
Allen Jones
'50 3100
'55 M38A1
----- Original Message -----
From: "haist" <haist2@home.com>
To: "TruckList" <oletrucks@autox.team.net>
Sent: Wednesday, April 18, 2001 6:22 PM
Subject: [oletrucks] Respirators
> Any of you painters on the list use a fresh air respirator and if so what
> type do you recommend?
> I hope ALL who use catalyzed paints are using such respirators since
> cartridge filters will not protect the user from isocyanates.
>
> I've been kidding myself for several years and now find that I'm hacking
for
> days after each exposure. Its called being "sensitized" to the chemical.
>
> I found a system called Hobbyair that is intended for the non-professional
> painter that is much more reasonably priced than the pro systems ($1K !)
>
> Any feedback appreciated.
>
> Thanks.
> <><
> Whitney Haist
> Orinda, CA
> Chevy trucks: 2-'46s & a '39
> www.jps.net/haist/artdeco.htm <http://www.jps.net/haist/artdeco.htm>
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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