The cleaners are a nuisance. I think they at least should wait for the dust to settle instead of scurrying and whirring everywhere. They are no better than mosquitoes or cockroaches except, I know, their purpose is just the opposite; it’s to protect us against infection or contamination. People used to think exposure to germs was a good thing, since it built up immunities, but today they say there’s no reason to worry about it.