Condensation can be a very serious issue which is exactly why we give all new tenants guidelines on how to spot and prevent its build up. It's important to ventilate the property, to keep it heated and to avoid creating too much moisture by drying clothes on radiators or not using extractor fans in kitchens and bathrooms. When mould starts to show it should be cleaned off straightaway using an anti fungicide spray. It can be a very frustrating and distressing issue, which is compounded by the fact that one occupier may have a problem, but the next occupant of the property does not due to the way that they live. So as the reviewer suggests do look for signs of mould as well as using your sense of smell. Also bear in mind how you will live, for instance avoid ground floor properties if you are not happy above leaving some windows open for ventilation. In this instance the situation looks to have got out of hand so we would ask the reviewer to email our lettings director.