i didn't touch the bottoms and the backs. like, put on socks, grasp box between socked feet, open box, remove the air bag packaging stuff, and if you want, UV it again. however, if you're using 185nm the ozone will get the "back" and inside. not the bottom, maybe, but if you're concerned, flip it over. If you're concerned, make sure you read research papers on exposure time of pathogens to UV-C and/or Ozone to population destruction. as i mentioned, the papers i read before i bought the bulbs said 10-60 seconds for covid. originally there was a recommendation for up to 3 minutes, but some research group went and tested shorter and shorter lengths of time. so you'd need to know the pathogen you're targeting and run it accordingly.