Drivers are up in deodorized arms over the criterion, which is one of dozens used by San Diego Regional Airport Authority officials to grade taxi drivers.
Anyone who fails the smell test can be ordered to change before picking up another customer.
The United Taxi Workers of San Diego says such tests reek of prejudice, fueling a stereotype that foreign-born taxi drivers smell bad.
Sarah Saez, an organizer with the union, told KPBS: “It’s demeaning and it is borderline racist, I believe.”
Inspectors have been sniffing drivers for years, but controversy arose recently when a union employee spotted the checklist in an airport board agenda.
One driver, Negus Gebrenarian, 39, from Ethiopia, told AP news agency that bad smells can just as easily come from customers.
Inspectors with the airport authority also monitor a vehicle’s “foul interior odours”, including petrol, vomit or mildew.
The officials check, too, such criteria as proof of insurance and faulty windscreen wipers or brakes.
The airport authority says it is merely enforcing the San Diego Metropolitan Transit System’s policy, which promotes frequent bathing by drivers.
Airport authority spokeswoman Rebecca Bloomfield said: “Taxi drivers are often the first impression that travelers receive when arriving into San Diego and we want to encourage a positive experience.”
Only about three drivers fail to get a passing grade each year, she added.
A survey of San Diego taxi drivers last year found 94% were immigrants and 65% were from East Africa.