Why are the smoke detectors going off, after I turned on the heat?

During the summer, when the heat is not used, dust builds on the heating elements.  When the heat is turned on for the first time of the season, the dust on the heating elements will be burned off, creating a smoke or fire smell.  Sometimes, the smoke smell is strong enough to activate the smoke detectors.  If that happens, reset the smoke alarms.  The smell should dissipate shortly.