Can't see a problem with what you are doing, just make sure your mask is rated for what you are spraying. Furnace, hot water heater - pilot lights all off and a single fan pulling are into the area.
Most of the EXPLOSIONS I have heard about come about when a person is cleaning a spraybooth. A shop down the street ran into a problem when the bonehead took a shopvac in to clean the overspray that had built up on the floor, another thought it would be a good idea to mix the 5 gallon bucket of finish with an electric drill.....BAM! Sparks and open flames are a NO NO.
