The tank atmosphere and excavation area should be regularly tested for flammable or combustible vapors until what condition is met?

Regular testing of the tank atmosphere and excavation area for flammable or combustible vapors is crucial to ensure safety during the removal of underground storage tanks (USTs). The correct condition for discontinuing these tests is when the tank has been completely removed from both the excavation and the site.

This is important because, even after a tank has been emptied, residual products can remain inside the tank or in the surrounding soil and groundwater, potentially leading to dangerous vapor buildup. By ensuring the complete removal of the tank, operators can confirm that the source of any remaining vapors is eliminated, thereby reducing the risk of explosions or other hazardous incidents.

Testing should continue until the tank has been removed to ensure that no hazardous conditions persist during the excavation process. Once the tank is no longer present, it is inherently safe to stop testing for those specific vapors associated with USTs.