1 plumbing vent stack for a whole house?

The inspection today was a residence/metal building had only 1 plumbing vent through the roof. All the rest of the drains had AAV’s, including the washer, and 3 bathrooms with a total of 6 sinks, 2 bathtubs, 2 toilets and 2 showers.

All of the water drained simultaneously when tested. This place was supposedly outside of the city code jurisdiction. A ‘plumber’ just redid most of the plumbing, even though there were several leaks. How many AAV’s are allowed? I generally just seen them in condos or in kitchen islands.

Should be fine, how big was the one vent pipe

Thanks for the reply, it was a 3"