If flammable vapors have penetrated a gas free space, which of the following actions would be the most hazardous to perform?

Correct Answer: Option A — Opening switches in the space to de-energize circuits.

Opening an electrical switch creates a potential spark at the contacts due to arcing. In a space containing flammable vapors, this spark provides the ignition source for an explosion. Electrical circuits must be de-energized from a remote, non-hazardous location before entering or working in a gas-free space.