ASME tanks filled on site must have the fill and fixed maximum liquid level gauge vent ____ feet from sources of ignition.

• A. 5 feet
• B. 8 feet
• C. 15 feet
• D. 10 feet

Answer: (D)

Setting a safe setback distance for venting during on-site filling is about preventing ignition of propane vapors. Propane is flammable and heavier than air, so any gas that vents from the fill line or the fixed maximum liquid level gauge can travel along the ground and accumulate near ignition sources if it’s too close. Requiring the vent to be at least ten feet away from sources of ignition gives vapor enough space to dissipate and reduces the chance that a spark, flame, or hot surface could ignite it. This ten-foot requirement is a safety measure used to protect workers and the site during filling operations, balancing practical work space with effective hazard reduction.