___ test (home inspection component)

RADON

This odorless, radioactive gas is often checked during home inspections to ensure safe indoor air quality. It can seep in from the ground and requires special detection.

This clue is looking for a type of test often done during home inspections to check for a colorless, odorless gas that can seep into basements. "Radon" fits because it’s a common health hazard tested for in homes, and the blank hints at a single-word answer. The clue plays it straight—no wordplay—just a direct reference to a standard part of real estate safety checks. If you’ve heard of radon mitigation systems, that’s the same gas being tested here.