After nearly going crazy trying to get the smoke detectors to stop going off yesterday, Will fixed them.
He took each and every one down, and used our air compressor to blow out the dust. Much more effective than vacuuming them apparently. He said that there was only one that didn't have a large cloud of dust poof out of it. The rest were so full of nasty that it didn't take much to set them off. When he was done cleaning them, he put them all back up.
And, they haven't gone off since.