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 electrical switches inside a gas-free space contaminated with flammable vapors creates an internal electrical arc. This spark is a primary ignition source that can instantly detonate the flammable atmosphere, making this action extremely hazardous compared to remote power isolation.