I am looking at a house in MA which was built in 1850 (obviously there have been significant upgrades since then). The downstairs bathroom and kitchen were updated within the last 5 years, but the plumbing was done incorrectly. There are no vents, automatic or otherwise. The homeowner had a plumber come and look at the situation and he suggested automatic vents. To the best of my knowledge these are not allowed, is that correct?
I am being quite wary of any major problem because of my last home which I recently sold in VT. There were issues with code violations on work performed well before I bought the home and I was forced to repair them before I sold the home because of a new town by-law. I am trying to aviod this problem in the future with this home by carefully inspecting the major systems. I don't want any surprise expenses when I go to sell. I know nobody can assure me of no surprises, but certainly someone has an idea whether automatic vents are legal or even allowed in MA.

Thank you in advance for the help.