I think this is a complete non-issue.
"Flammable liquids" covers everything from gear lube to ether. Different rules apply based upon the specific material, the type of container, whether the containers are closed or being tapped into, etc. As the first reply stated, there are other standards that go into these matters in greater detail.
Likewise, anything whose minor fumes can be ignited by a tripping breaker would already be required to be in a special double-wall storage cabinet, and mechanical ventilation of that cabinet -ever notice the threaded fittings on the cabinets- might also be required.
Perhaps you are worried because you can smell fumes near the panel. Well, in that case it all comes down to an engineering study, performed by someone competent in this area, that defines the classification of the area. The NEC tells us much about wiring methods in different zones, but does not tell us how to define the extent of each zone.