Industrial air pollution releases are regulated by the City of St. Louis Health Department, Air Pollution Control Division (APCD). APCD issues pollution control permits for various categories of businesses, and sometimes reviews demolition permits for large buildings or multiple demolitions on the same city block.
Automobile emissions testing is conducted by the Gateway Clean Air Program, under contract with the Missouri Department of Natural Resources. RapidScreen vans test vehicles at various on-ramps throughout the St. Louis region, and there are two testing stations in the City:
4642 West Florissant Ave (near I-70 at West Florissant)
3242 South Kingshighway Blvd (behind Home Depot; access via driveway immediately south of Juniata St.)
If your vehicle passes the RapidScreen test, and you renew your car registration before your RapidScreen notice expiration date, you will not need to visit an emissions inspection station that year.