Which of the following should NOT be present during work on gas-containing piping?

When working on gas-containing piping, the presence of electric switches should be avoided to minimize the risk of ignition during maintenance or repair tasks. Electric switches can create sparks or generate heat, which poses a significant safety hazard in the presence of gas. Flammable gases can accumulate, and if an electric switch is activated, it can ignite those gases, leading to potential explosions or fires.

In contrast, proper ventilation is crucial in order to disperse any gas that may escape, thereby reducing the risk of accumulation and creating a safer working environment. Flame-proof tools are specifically designed to minimize the risk of igniting gas and should be utilized to ensure safety when working on gas systems. Safety gear is essential for personal protection against potential hazards associated with gas work. Thus, the absence of electric switches is a necessary precaution for maintaining safety in environments where gas is present.