Inspection and evaluation requirements for portable containers, shop-fabricated tanks, and field-erected tanks with a maximum capacity of 75,000 gallons are provided by the Steel Tank Institute (STI STD SP001). Aboveground storage tanks must undergo STI-SP001 examinations to assess their suitability for continuing service (ASTs). Inspections are carried out to determine the state of the ASTs and any changes. Tank inspections described by this standard are used to detect degradation of tanks and appurtenances, ensure compliance with 40 CFR 112, and ensure proper installation of systems according to manufacturer's recommendations and industry norms.

Out-of-service tank inspections, also known as internal inspections, are complete official inspections of all accessible internal and external parts of tank surfaces, piping, and appurtenances undertaken by authorized inspectors. This sort of inspection necessitates the removal of tanks from service to undertake a complete inside evaluation. Tanks are inspected for structural integrity and serviceability. Tanks are checked for leaks, corrosion, and any other possible or probable fluid or product leakage that could harm the environment.

An authorized inspector conducts an in-service inspection, also known as an external inspection, which includes a visual inspection of the tank's outer surface. This inspection is typically carried out while the tank is in use or when the interior of the tank is not accessible or accessible for inspection. APEX inspects the tank systems for evidence of leaks, shell distortion, signs of settlement, corrosion, and the condition of coatings, insulation, and appurtenances during the in-service inspection.