During the Smog Check, at what ambient temperature should the approved fan be used?

• A. Above 50 F
• B. Above 60 F
• C. Above 80 F
• D. Above 72 F

Answer: (D)

Ambient temperature affects how quickly the engine and exhaust system reach stable, test-ready conditions during a Smog Check. When it’s warm, extra cooling help is used to prevent overheating and to keep readings consistent, so an approved fan is recommended once the temperature rises above a specific threshold. That threshold is 72 F, meaning you should use the approved fan whenever the ambient temperature is above 72 F to maintain reliable, repeatable test conditions. Using it at or below this temperature isn’t required, and waiting until 80 F would miss the rule for the many days in the 72–80 F range.