I am a cabinetmaker by trade...we deal with this a bit in my industry. The relevant regulations, I believe, are about V.O.C. emissions (volatile organic compounds) for wood finishing. These have gotten tighter and tighter over the years. My current firm has given up spraying anything but waterborne primer because of the change in regs over the past few years.
Many (cabinetry/millwork/furniture) shops have switched to waterborne finishes for this reason. They aren't the same, but they are less toxic/explosive.
The finishing industry has also developed hundreds of new products with lower VOC levels, not to mention overspray collection systems, etc.
You are right, it is not "illegal" to buy or shoot lacquer per se. However, it is all about the type of product, the amount it gets used, how you deal with waste disposal, etc. It is technically illegal to spray commercially without complying with the current regs. (which I can't quote without lots of digging). The reality is that iit is unlikely that anyone will come after you if you are spraying on a small scale.
Arnold's points about toxicity and danger are +1 for me, too. The reason the regs have tightened is because of this, both for the folks spraying and for the rest of us living here (earth)
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I saw that you did some searching on Google. It may be fruitful to try searching for "V.O.C. regulations for wood finishing," for example. The keyword is the acronym V.O.C..
Lots of examples. Here is one general discussion that provides some overview:
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The larger and more personally significant issue may be your insurance coverage. Most/all policies have disclaimers about not doing anything in the home (assuming you are working from a home shop at this point) that defies "currently acceptable safe practice" (read compliant with current regulations). Business policies have similar disclaimers about doing anything that defies current O.S.H.A. regs. (like ignoring current allowable VOC levels.). Having been through a few insurance incidents as a manager in various companies, I can report that these disclaimers are the first things that many adjuster look for to avoid payment in case of an accident.
Current "safe" practice would mean explosion-proof bulbs and fan, acceptable V.O.C. emission levels, appropriate respirator use, appropriate toxic waste disposal, product selection, overspray recycling, etc. In other words, if something burns/blows, all the insurance premiums paid won't be worth the proverbial hill of beans if the adjusters figure out that you were shooting lacquer in any remotely bootleg manner.
The other issue is zoning, which certainly does vary regionally. Where I live, spraying lacquer commercially (for any paying work) in a residential neighborhood is not okay. Rub the neighbors the wrong way and you are all done.
So the point that "we did it for decades with no problem", while well taken, may not fit here. More has been revealed about links between disease/toxicity as well as all that we are learning about pollution. The reason the regs changed is because these products are bad news for humans, for a start.
The problem is that the toxic stuff (especially the hardcore toxics like the catalzed finishes) are the best for (furniture and millwork) finishing, for clarity, durability, economy, and drying/cure times. My industry has been in an uproar about this for about 20 years.
The acoustic issues of varnish vs. lacquer are outside my knowledge so I will stay out of that. However, as a Plant Manager for an architectural millwork shop, I know a little about lacquer and V.O.C.'s. Just enough to stay out of trouble with the local government and the insurance company.
Whether any/all of this is relevant to the fellow/gal spraying a bass or two in his/her garage shop is really up to local government and the relevant insurance companies. Hope that this helps...
