How old do you think is old enough to use a vacuum cleaner?
4 or 5 as long as an adult is the one plugging it in and there aren't too many obstacles in the room. My 8 year old son has been vacuuming our living room since then (he begged to do it). He misses spots here and there, but the way I see it, even if he only gets 75% of the carpet cleaned, that means I only have to do 25% instead of 100%.
I was putting together family vaccuums and using them in gradeschool. So anywhere around 10 years old should be fine. This is assuming your kid has some muscle though. unless the vaccuum is power driven, they might not have the heft.
I would say 10 years old. kids younger than that wont really understand how important it is. i mean, its not CIA stuff, but you know, getting the corners, taking care of it, not banging it around. I think 10 year olds understand that its for cleaning and tidying, not a toy you push around that makes lotsa noise to scare the cat or dog. and they gotta have a little muscle, at least right? i dont know about you but i dont have those fancy dyson vacuum cleaners that are light and easy to maneuver. so yes, 10 years old :) for me. ahhah
Whatever age they can push it around. They don't have to do a superb job - just praise whatever they do! We bought a new vacuum where you can see the dust go inside it - my 8 year old loves it! He especially loves the clink when it sucks up a big crumb or something. However, I would caution that you want to teach them to clear the area of toys and other small objects that might break the vacuum, before starting.