Tank tightness testing may only be used as a sole method of release detection if it is used every ____.

• A. 15 days
• B. 45 days
• C. 60 days
• D. 30 days

Answer: (D)

The main idea being tested is how often a tightness test must be performed if it’s used as the only method to detect releases. When you rely on tightness testing alone, the test needs to be done on a monthly basis—every 30 days. This frequency keeps the window during which a leak could go undetected as small as possible, balancing practical testing effort with the safety goal of quick leak detection. Testing more often, like every 15 days, isn’t generally required and adds burden, while testing less often, such as every 45 or 60 days, could allow a leak to go unnoticed longer and raise environmental risk and regulatory concerns. If other release-detection methods are used in addition to tightness testing, the interval requirements can change, but for sole reliance on tightness testing, 30 days is the standard.