What action should be taken if 90 percent fuel gas by volume is detected within the piping during purging?

When 90 percent fuel gas by volume is detected within the piping during purging, the appropriate action is to stop purging operations immediately. This is critical because a high concentration of fuel gas poses a significant risk of explosion and fire.

Purging is performed to clear the piping of flammable gases or vapors and to prepare for the introduction of a safe inert gas or air. At 90 percent gas concentration, there is a strong potential for reaching the lower explosive limit, making the environment very hazardous. Stopping the purging process allows for the implementation of safety measures to assess the situation, such as ventilation or seeking professional assistance to avoid any risks of an ignition or explosion.

Continuing purging in this scenario could exacerbate the danger, and venting gas or increasing pressure would further complicate the danger without proper safety protocols in place.