The active ingredient in NIX is permethrin. I don't apply it directly to the snake as permethrin poisoning causes neurological damage or death in snakes, I would certainly keep it away from the heat pits, eyes, and mouth.

If kept out of direct sunlight the half-life of permethrin is 30 days. Spray the enclosure, hides, and paper you are using for substrate. Once the enclosure, hides, paper, etc. have dried you can set your snake's enclosure back up. DO NOT SPRAY THE WATER BOWL.

Keep a supply of treated and dried paper and hides on-hand so they can be replaced when your snake makes a mess. Re-treat the enclosure in 2-3 weeks.

Mites have several periods in their life-cycle where they leave the snake. When they come into contact with the treated paper and surfaces in the enclosure, the permethrin kills them.

To give your snake relief you can soak it in lukewarm water with just a drop of mild dish soap added so that the surface tension is reduced, and the mites drown quickly.