For what it's worth, my understanding is most hot plate/magnetic stirrers in common use in organic chemistry labs are not explosion proof/approved for hazardous locations. They are potential ignition sources when used with flammable solvents, but when operated in properly functioning fume hoods, the solvent vapors are swept away at a sufficient rate such that the ignition sources don't typically encounter vapor concentrations in the flammable (> LEL) range. I'm not saying that's a good policy, but I believe it is why (along with the use of reflux condensers) there isn't an epidemic of fires when flammable liquids are used with these devices.
Donald Abramowitz
Environmental Health & Safety Officer
Bryn Mawr College
Bryn Mawr, PA
What is your policy on heating or mixing flammable liquids with non-explosion proof, not spark proof stirrer hot plates?
Tom Bialke, MSPH, CIH
Mgr. Research Safety and Compliance
Kent State University