Glossary

All Appropriate Inquiries (AAI)

Also known as: AAI Rule, AAI

The federal regulatory standard governing the environmental due diligence a prospective property purchaser must conduct prior to acquisition in order to qualify for CERCLA's innocent landowner, bona fide prospective purchaser, or contiguous property owner liability defenses.

AAI is the compliance standard that gives a Phase I Environmental Site Assessment its legal significance: conducting a Phase I ESA that satisfies the AAI rule (which incorporates the ASTM E1527 standard practice) before closing is what preserves a purchaser's ability to claim it exercised appropriate care and should not be held liable under CERCLA as an owner or operator for pre-existing contamination it did not cause. The AAI regulations specify not just that an assessment be performed, but detailed requirements around its timing (generally within one year of acquisition, with certain components refreshed within 180 days), the qualifications of the environmental professional conducting it, and the specific inquiries that must be documented, meaning a Phase I ESA that skips or shortcuts these elements may fail to establish the liability defense even if it otherwise looks thorough. Because the liability protection depends on satisfying AAI before the purchaser takes title, buyers and their counsel treat the timing of the Phase I ESA as a hard deadline in the transaction schedule rather than a diligence item that can be completed after closing.