I have a great way to get rid of nats, it take 3-4 days but over the days you'll see the numbers decrease.
Step #1
Get a small glass or mug (clear seems to catch more i have no idea why!!)
Step #2
Pour some vinegar (apple cider vinegar I use) into the mug about 1/3 full is good maybe a little less.
Step #3
Drop a few drops of dishsoap into the mug (to add a little zest
)
Step #4
Put the mug into the area with the most gnats (you can put mugs/glasses in different rooms if they are in those as well)
Step #5
Let the mug do its magic
I get gnats a few times a year due to where I live, I started doing that a couple years ago and have done it since. It does smell a little but not to the point where you cant be in the room. For some reason they are attracted to it and go down for a drink, then they go sleepy