A couple of years ago I lived in a student house. I was on the ground floor in the front, right on the street. As a young lady, in not the most fantastically salubrious of areas, I almost never opened my curtans, much less my window! So my room developed a mould problem. I let my landlord know about it, and his wife let me know about bleach. It worked. Although it did continue to give me breathing problems. I had a cold for the whole first semester, which was eventually diagnosed as chronic rhinitis but maybe it was mould-caused.