Although I’m well aware of the toxicity of spray lacquer when spraying, and use a respirator and venalate my shop extremely well while applying it, I’m trying to find out how long after the lacquer is applied does the toxicity last.
Here is the situation:
My spray area is in a the garage below my house – because of this I have widows open and multiple fans running (as well as a portable explosion proof exhaust fan sucking air right at the point of spraying) to minimize drift within the shop and home. Of course no matter how careful I am I still get some vapors within the home. For this reason my family leaves until 3-4 hours after I finish spraying.
You can still smell a slight smell of the lacquer in the house for ~24 hours. I also must note the work I have sprayed remains in my shop below my house while curing.
My question is – can I assume as long as you can smell it it should be considered toxic, or is there a point in the process (say after 1 hour curing, etc.) where the toxicity is very low??
As much technical info and opinion that can be provided would be appreciated.
Replies
If you can smell it, you're being exposed to solvents. Some are not terribly toxic, like acetone. Some are very very nasty, like ethers. There are published toxicity thresholds for all those solvents. Read the MSDS for your particular lacquer and solvents. I'm probably too cautious, but better that than too careless. Particularly if you expose your family to that stuff. Once it is cured, its generally nontoxic. I don't spray in the house.
For example, diethyl ether has a smell threshold of .3 ppm but toxicity starts at 3 ppm. Butyl Acetate has a smell threshold of 5 ppm and toxicity at 100 ppm. These are solvents with good "warning" characteristics. On the other hand, methlyene chloride (carcinogenic) has a smell threshold of 250 ppm but toxicity for long-term exposure starts in the under 1 ppm range. So, just because you can't smell it anymore is NOT an indication of safety with some solvents. Glycol ethers have very little smell but toxicity begins at levels as low as 0.02 ppm. To give you an idea of the risks, a 10 by 30 foot room has about 100 cubic meters of volume. 0.1 grams of solvent gives 1 ppm. Spray one ounce of lacquer in an unvented room. That's about half an ounce of solvents or 12 grams. That gives 120 ppm of solvent vapors. MANY of the solvents used have not yet been evaluated for carcenogenic properties in humans. Many cause reduced fertility, maternal toxicity, early embryonic death, birth defects, kidney or liver damage in animals.
So, final opinion is "do not spray lacquer in the house". Fan or not. Even if you can't smell it anymore, it is NOT an indication of safety. To get to under 0.01 ppm of solvent vapor, you need 10,000 air changes in a 100 cubic meter room. At 300 CFM, it takes 10 minutes per air change. That solvent vapor is hanging around a looooong time. A day or two with the fan running.
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