• • TVOC concentrations in Garage B reached 2398.1 μg·m−3 (weekday) and 3401.6 μg·m−3 (weekend), exceeding typical indoor levels by orders of magnitude, indicating severe VOC accumulation in commercial underground garages.
• • CO concentrations peaked at 10.1 mg·m−3 (Garage A) and 12.6 mg·m−3 (Garage B), both surpassing the Chinese 1-h indoor limit of 10 mg·m−3, posing acute exposure risks during rush hours.
• • Non-carcinogenic hazard indices (HI) were 0.03 and 0.18, below the EPA safety threshold of 1, yet carcinogenic risks reached Level II (Garage A) and Level III (Garage B), driven by benzene, 1,2-dichloroethane, and naphthalene/ethylbenzene, necessitating priority control.
• • BTEX compounds dominated VOC profiles, accounting for >90% (Garage A) and >70% (Garage B) of TVOCs, highlighting gasoline combustion and evaporation as primary sources, with implications for targeted mitigation strategies.