Classification 9.2 applies if regulated limit is exceeded. Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back.
Most vapors are heavier than air.
Vapor explosion hazard indoors, outdoors or in sewers. Runoff to sewer may create fire or explosion hazard. Containers may explode when heated. Many liquids are lighter than water. Inhalation or contact with material may irritate or burn skin and eyes.