A double-walled steel tank built according to UL standard 58 requires what before installation?

Before the installation of a double-walled steel tank built according to UL standard 58, it is essential to perform air testing of the interstitial space. This testing is crucial because the interstitial space is the area between the two walls of the tank, and it serves as a secondary containment to prevent leaks from escaping into the surrounding environment. By conducting air tests in this space, operators can confirm that the secondary containment is intact and functioning properly, ensuring that it can effectively contain any potential leaks from the inner tank.

This testing is an important safety and regulatory requirement, as it helps to protect groundwater and mitigate environmental risks associated with underground storage tanks. Proper testing verifies that there are no breaches in the interstitial space that could lead to hazardous substances being released.

In the context of the other options, routine maintenance is not a prerequisite before an installation—maintenance typically relates to ongoing care after the tank is installed. Air testing of the inner tank is important as well but is not specifically mandated before installation compared to interstitial space testing. Finally, stating that no testing is required neglects safety protocols and industry standards, which emphasize the importance of confirming the integrity of the tank system prior to putting it into service.