Ah, it's a terrible smell, isn't it? The smell of turning on the heat for the first after a long, dusty summer. The main target here is the combination heating/cooling units. I'm not talking about heat pumps, I'm talking about the kind which sticks through a window or a hole in the wall. When you first turn it on, it redirects air to the outside for about thirty seconds. A built-in timer would only activate the outside feature when the heat's been off for more than three days.-- fogfreak, Sep 04 2003 + It could also be set to blow itself out about once a week over the summer to prevent the dust from building up in the first place.-- AO, Sep 04 2003 Couldn't you just cover it up over summer to prevent the dust settling on it?-- Loris, Sep 04 2003 [Loris] At home, I have a heat pump. But today at school I was in studyhall (in the back of the computer lab). The air conditioning was on full blast, and, being anemic, I turned on the heat for just a second. "Nobody'll know" I thought. Man was I wrong. I quickly turned around and posted this idea. So, in response to your question, nope, I couldn't cover it up. Besides, the air conditioner won't work unless it has free circulation on both sides. At my school, it's a miracle that they work anyway.-- fogfreak, Sep 04 2003 halfbakery