Does an onion completely remove "fresh" paint VOCs and other chemicals emitted? I have read that paint contains VOCs(Volatile Organic Compounds), and solvents generally, and I could wait for them to dissipate, but i've read there are ways to remove the smell of paint such as half an onion in a bucket of water, such as slices of lemon on a plate, such as small bowls of distilled white vinegar.

Do these techniques actually remove all the nasty elements from the paint fumes, or just some of the nasty elements from them?  Do they remove all the paint fumes?  

I wouldn't want to remove the smell but leave the VOC or other bad elements there.  If that's the case i'd rather just leave a window open in the room, closing it periodically, seeing if there's finally a time when the paint smell doesn't build up when the window is closed, then i'll know the paint isn't emitting any more fumes.
I've never heard of onions, lemons or vinegar removing a paint smell, but I would guess that they'd just cover up the unpleasant odor with something nicer.

As to your later comment:


  I wouldn't want to remove the smell but leave the VOC or other bad elements there.


VOC stands for "volatile organic compound." (See the Wikipedia page on VOCs) Volatile compounds are ones that evaporate easily. Technically, the smell of that onion (or lemon, or vinegar) is a VOC, just not a particularly harmful one. (Not knowing the particular chemicals that make up a onion's scent, I can't say for sure that it's a volatile organic compound, but it's a pretty good bet.)

That fresh paint smell comes from VOCs (and potentially from other volatile compounds), so by the time the smell is gone, any VOCs you couldn't smell are likely gone too.