This studio flat is located in the basement of a large house that has been divided into flats. The boiler room for all of the flats is located in the apartment, hidden behind a pair of double doors.
As others have mentioned, the plumbing can be noisy, particularly a loud banging noise that's presumably caused by a water hammer effect.
The noise is mostly only during the day, but it could still be an issue if you wished to sleep in.
Others also complained about the temperature due to the presence of the boiler, although I didn't find this an issue in winter, as I just left the window open.
There was a hidden rule about sending the host a copy of guests' IDs buried in the check-in details, which needs to be displayed prominently as a house rule. They also tried to get me to give them my phone number, which is against Airbnb's policy.
Despite there being a notice in the apartment warning guests to clean up any hair, I did find someone else's in the shower, indicating poor cleaning.