Legal Question in Administrative Law in California

Snitch them off to the California Division of Labor Standards Enforcement.

Also to Cal-OSHA.

Labor Code 6404.5 prohibits smoking in "enclosed places of employment" in California. There are a few exceptions, but generally it is an infraction with a not-to-exceed $100 fine for a first offense and according to 6404.5(j) it is to be enforced by local law enforcement agencies including local health departments, as determined by the local governing body (city or county), so you should inquire locally before deciding that Cal-OSHA or Labor Standards Enforcement is the place to go (although Cal-OSHA could become involved if there are repeat offenses). You should look up and read this Labor Code section before proceeding so you are fully up to speed on the prohibited conduct and the enforcement structure.