If it is necessary to enter an aircraft's fuel tank, which procedure should be avoided?

Entering an aircraft's fuel tank presents significant safety risks due to the flammable nature of aviation fuel and the potential for confined space hazards. Conducting defueling and tank purging operations in an air-conditioned building is not advisable because air conditioning can mask the presence of fuel vapors that may be hazardous. Proper ventilation is critical to ensure any potentially dangerous vapors are dispersed effectively, while air conditioning might recirculate contaminated air within the confined space.

The other procedures mentioned are essential safety measures. Continuously purging the tank helps to keep the atmosphere inside the tank safe by removing harmful vapors. Having an assistant stationed outside the tank provides an extra level of safety, as that person can call for help or conduct a rescue if an emergency arises. Additionally, wearing a safety harness is a crucial precaution to prevent falls while working inside the tank or during any unexpected situations. Thus, avoiding the practice of conducting such operations in a controlled, air-conditioned setting aligns with promoting a safer working environment when entering fuel tanks.