If a UST remains in temporary closure for months or more, vent lines must be left open and functioning for how many months?

• A. 1 month
• B. 3 months
• C. 6 months
• D. 9 months

Answer: (B)

Keeping vent lines open during temporary UST closure is essential to prevent vapor buildup and pressure changes inside the tank system. When an underground storage tank is not in use but still in place, vapors can accumulate and shifts in pressure can stress piping and fittings or release vapors to the environment. Leaving vent lines open and functioning for three months provides a safe window to manage those vapors and maintain the system’s integrity as you plan reactivation or further maintenance. Shorter periods, like one month, wouldn’t ensure adequate venting for an inactivity stretch, while longer periods aren’t the minimum requirement the standard calls for.