: Ditto, the same question. I've been wondering, too. In The Epoxy Book, under
: "Safety" the System 3 people specifically state that there's no
: harm in the vapor--in fact, no vapor to speak of. They are very strict
: about nt getting it on your skin, however. Rob says, in the instrux for
: his boats, that you should use a respirator, and I think he's using System
: 3 products.

: So: does anybody really know?

Older epoxies used solvents to reduce viscosity, and these organic solvents were malevolent compounds. The "100% solids" have no volatile organic solvents (MEK, toluene, xylene, MIBK, etc.) and so are far safer to work with. The epoxy resin is relatively harmless, but the curing agents, particularly the amine-based formulations found in most boatbuilding hardeners, can cause sensitization. Cycloaliphatic amines are nasty too, but you're not likely to run into them building boats. There is a far broader range of during agents and diluents than of epoxy resins. Curing agents come from all sorts of mineral and vegetable sources, and they are not benign. Their specialty is reacting with epoxy, but they're not particular about reacting with whatever else they bump into. If they can cause rash on your tough hide, imagine what they could do to your tender lung tissue. You can't go wrong by wearing a respirator. Make that a real one, with activated charcoal "Organic Vapor" cartridges, the black ones.

This also applies when sanding epoxy, because the stuff frequently takes days for full cure, and a lungful of partially cured epoxy dust is much worse for you than the hardener fumes. Consider this. Asbestosis is a lung disease caused by breathing asbestos-like particles. Microscopically these particles are not much different than epoxy sanding dust. Notice the operative word "asbestoslike particles". It is not just the chemical composition of the particle that is harmful, but its size and shape. OSHA has determined that the TLV for this irritant is 0.00. There is no known safe concentration, infection can be caused randomly by just one discrete particle. There has been a lot of press here recently about Libby, Montana, where 3/4 of the population has some type of lung problem, from an asbestos mine 10 miles out of town that has been shut down for years.

So what is the upside? Temporary comfort and convenience. The downside is nasty lingering death. Tough choice, huh?