It is a gas which is liquefied under pressure in a similar way to propane, so tanks and rail cars must be completely airtight at all times.

Otherwise the entire liquid cargo will rapidly be expelled under pressure as a liquid from any opening on the bottom of the vessel, or the entire liquid cargo will still evaporate quite rapidly and eventually all escape as a gas stream through defects or open valves on the top part of the vessel.

Any VCM liquid spilled will act like propane and rapidly turn into a gas which will disperse much wider through the air much more rapidly.

Not much is going to soak into the soil or be carried away by water drainage channels.

If it was an acetone spill or something like that it wouldn't evaporate nearly as fast, nor present as widespread an atmospheric content downwind, and you would have to get a lot closer to the spill to detect the vapors or smell it yourself even for a briskly evaporating liquid like acetone.

But the VCM is not only flammable, it is actually a highly toxic gas.

VCM smells exactly like most brand-new PVC shower curtains, because VCM's exactly what you're smelling in very small concentrations, as any residual monomer often outgasses strongly the first few days after hanging the curtain.

In an unventilated bathroom I would think that's often beyond the recognized working VCM levels allowed in industrial facilities.