Apparently enough of it will kill them. This was trying to use it to kill off black widows on produce, not in a garage:

https://mbao.org/static/docs/confs/2005-sandiego/papers/065LeeschJ THE TOXICITY OF OZONE TO BLACK WIDOW SPIDERS.pdf

But I dunno if it’s the best pesticide to use. I know that ozone is pretty reactive and can damage some substances. I remember rubber being one.

kagis

https://www.nrc.gov/docs/ML1820/ML18207A768.pdf

Looks like it’s also not great for steel, zinc, nylon, and some other stuff.

EDIT: Note that they were using 12,000 ppm for 1 hour to achieve 100% elimination of black widows. It sounds like it’d be extremely hazardous to be working with that kind of concentration.

https://www.cdc.gov/niosh/idlh/10028156.html

Patty [1963] reported that 15 to 20 ppm is lethal to small animals within 2 hours [Witheridge and Yaglou 1937]. AIHA [1966] also reported that on the basis of animal data, exposure at 50 ppm for 60 minutes will probably be fatal to humans [King 1963].

So that’s something like 240 times the concentration to kill a human in that period of time. Even if one can get the hardware to produce that kind of concentration in a garage, I wouldn’t want to do so.