I was thinking about this the other day. By virtue of producing the vapor something is being heated, probably close to red hot. A red hot object under the right circumstance, air/fuel mix, might be enough to cause ignition. In a PV the coil is hidden by the wich and tank or carto but outside air is introduced when it is inhaled upon. The chance of a problem is probably extremely low bordering on infintesimal to while not "intrinsicly" safe its probably "practically safe. I smoke analogs while fueling up the lawn tractor, not the brightest idea I know, but wouldn't smoke at the gas pump, and I live in NJ (The Regulation State) where we don't pump our own. The "shock" value could cause some amusing situations for the vaper, but it's probably not a good idea just because of bad publicity which I hadn't really considered either.