A lot of the chemicals we use in woodworking, especially in finishing, are toxic. Now there is toxic and TOXIC. There is long term exposure toxicity and one-whiff-drop-dead toxicity. If you want to work safely, you need to know. Not only do woodworkers need to know, everyone needs to know. So We the People, in the guise of "the Federal government," passed a law that requires that for any substance you sell, you must also make available a Materials Safety Data Sheet or MSDS Sheets for short. (Yes, I know the extra word "Sheet" is redundant.) With the introduction of another intrusive government-sponsored initiative known as "The Internet," it's now possible for companies to make MSDS sheets readily available through downloads.

MSDS sheets have information on the chemical makeup of the substance; the long term and short term dangers the materials pose; what safety precautions should be used when handling or storing the substance; and what to do in case of accident. This is phenomenally usefully information for anyone handing any chemical, especially if you are working in your house with suboptimal ventilation or protection or if other members of your family can get exposed.

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For example: With all the writing I have done on shellac and alcohol I also took a look at the safety aspect of the various alcohols on the market. If you look at the MSDS sheet for Klean-Strip S-L-X Denatured Alcohol  (DNA) which is inexpensive and commonly available at local hardware stores (FWW used it in their article on shellac in Dec. 2010), you will discover that it contains 45-50% methanol. The MSDS sheet for the product says, "Vapor harmful. May cause dizziness, headache, watering of eyes, irritation of respiratory tract, irritation to the eyes, drowsiness, nausea, other central nervous system effects, spotted vision, dilation of pupils, and convulsions." There's also water in the alcohol, which makes the shellac harder to use - but water is the least of my issues. I just don't want the methanol fumes invading my house and shop. Incidentally the author of the FWW article isn't wearing any protection (gloves, mask, etc.), which I think is an error. More than one person has come to me after applying shellac and complained about various symtoms, not understanding that they got poisoned by the alcohol, which can be absorbed by the skin and eyes from vapor in the air. 

The two most  alcohol specifically used with shellac is Bekhol, a premium shellac sold by Behlen and available from lots of higher end woodworking suppliers (but not us for some reason).  It is safer and better than the hardware store stuff. If you read the MSDS for Bekhol  you find it only has traces of methanol in it.  It also doesn't have significant amounts of water.

Another great solution which I regularly recommend is Everclear - which is a totally drinkable pure ethanol alcohol available in some liquor stores. It unfortunately isn't sold in every state. There are two versions of Everclear 151 proof and 190 proof. The later is 95% ethanol the rest being water. This works great for shellac. The 151 proof - about 75% alcohol and the 25% water content is just too much for shellac.

Ethanol is what's in liquor, so the exposure limit is pretty high, but one message that comes out loud and clear is that if you use it a lot you should wear lung and hand protection - and of course eye protection just in case. (The stuff is a lot stronger and dangerous to splash in your eye than than your typical mixed drink, although there is no danger from ice bruising.)

The big difference between Bekhol and Everclear is that Bekhol is 30% non-ethanol, of which some is isopropal alcohol, which raises the flash point. That means that the stuff will take a little longer to evaporate, and when you are spraying shellac, this might be an advantage. (You don't want to have the spray to dry before it hits your wood).

Read the MSDS sheets of the products you use. Don't ignore the safety recommendations just because they come from "The Man." There is a certain air of over-caution in these documents, but they are important. Most of the toxicity of chemicals we use around the shop is cumulative, which means when you find out you have a problem it's too late to fix it.