Over the last week or so, we have been getting a strong smell that resembles paint thinner in our bathroom and kitchen. We haven't done any decorating or stored any chemicals anywhere in the flat. The only thing that has happened is that the extractor fan has blown and is no longer working. At some times the smell is really strong and then it can fade away for a few days and then come back stronger again. The heating system is all electric powered so it definitely isn't a gas leak (unless it is a sewer gas leak). Does anyone have any ideas to what may be causing this smell?