Which statement about interstitial monitoring is true?

• A. It is optional for all tanks
• B. It monitors the space between the primary tank and secondary containment for leaks
• C. It is only used for above-ground tanks
• D. It detects leaks in the product line only

Answer: (B)

Interstitial monitoring focuses on the space between the primary tank and its secondary containment to catch leaks early. This interstitial space is designed to hold any liquid that escapes from the tank or its connected piping, so monitoring it lets you detect a release before it reaches the environment. That makes the statement true: the system is specifically watching that space for leaks.

This isn’t optional for all tanks under typical regulations, and it isn’t limited to above-ground tanks. It also isn’t limited to leaks in the product line alone; the monitoring protects the integrity of the tank and its piping by signaling when something has escaped into the interstitial area.