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Alan in Marlborough, New Zealand

In winter when the heat pump (air con) inside unit heats the inside of the house the outside unit blows cold air across the outside wall and window of a bedroom. There is black mould spotting on the weatherboard outside wall and on the curtains inside the window. Today I will adjust the outside unit at an angle so the cold exhaust blows away from the window. I discovered the mould when I was painting the window frame. I am certain that the influence of cold air in winter when heat is needed in the house gets black mould going with health problems for residents. I will try a 3% spray of hydrogen peroxide on the curtain liner on a small trial patch to see how that works. HHOO is a bleach.