I had a bad problem with spidermites and gnats and tried a lot of stuff then came across a bug bomb that was made for the grow room
Doktor Doom Total Release Fogger
Stock the Doktor Doom Total Release Fogger in your pest-control arsenal for a doctor that's on-call 24-hours a day. The active ingredient, pyrethrin, is derived from chrysanthemums and proven to successfully destroy spider mites, aphids, whiteflies, fungus gnats, and more.
I just covered the lights etc with bags and set off the fogger and it worked like a charm
This fogger is safe for use in greenhouses and indoor gardens, around all plants including fruits, vegetables, and ornamentals.
The 3-ounce can treats a 3,000 cubic foot area.