Clean Truck Check in Napa, CA

Air quality context in and around Napa

Annual aggregate readings from EPA Air Quality System monitors within about 25 miles of Napa, reporting year 2025. Clean Truck Check exists to reduce real-world emissions from heavy-duty vehicles — the numbers below are the local baseline those rules are designed to improve.

Ozone (O₃)

0.04 Parts per million

1 monitor · 31,897 observations · 0 days above standard

Source: EPA Air Quality System (AQS) API. Reporting year 2025. Last fetched 2026-05-18.