Misting raises humidity. For about 5 seconds. Then it is evaporated and the air has moved around so much that the effect is no longer relevant.

I mist junipers when it is hot, by hosing them down with my wateringcan (rain water). Juniper can take up to 40% or so of their daily need through the foliage, so I tell myself they like it

There was a fad once to grow air ferns from tropical forests where they grew on tree trunks. The only way to water them was misting with spray bottles. I wonder if the idea of misting spread from that.

I think if central air and heat are off humidity would stay up for a while, but I don't know how long. Probably it would be 5-10 minutes, but maybe longer.

What about the following 'Myth'

"Get more plants indoor for Air purification (remove toxic out of the air.)"
You see that alot on Labels for "indoor" plants.

Myt or is this true?

While it is true that plants do air purifications, if you put your entire house full of plants, that you almost can't walk indoor anymore.
Than you have 0,00000005% more clean air.
So while it is true, it has no benifits at all.