I'm sick reading your comment. I can't imagine leaving an infant like that - or any child who doesn't talk and wouldn't be able to report their experiences.
The first day I brought my daughter to pre-school I thought she would grab onto me and not let go. Instead she took one look at the place, said to me "Oh wow - children" and went running into the playroom. An hour later when I came back she tried to push me out the door and said "go away". I was crushed.
I know. Those poor infants and their tiny ears. If you were a parent of one of those babies, you'd probably never even think to ask about anyone vacuuming while the babies were in there, let alone, on the floor in bouncy chairs. Which is why, if you feel you absolutely must place your children in daycare, etc., then always plan to make surprise visits.