half life of 30 mins....
That is highly dependent on conditions. At -50C in a closed chamber with no contaminants, it is over a month. At 100C it's just a few minutes. Also affected by humidity, the number of organics and oxidative (right word) materials it comes in touch with.
I think to do it right if you want it as a primary defense, you need to get a meter. That ensures that the levels get high enough and ensures they get low enough before your re-enter the space. The only downside is the meters are way more expensive than the generators. About $400 for a basic one. I'm winging it for now and thinking of it as an "extra" not a "primary" measure. But if I find that months down the line I'm still using it, I might invest in a meter.
The general rule seems to be that you should not enter a room until concentration falls below 0.02ppm and that takes about an hour if you disinfect to a 0.5ppm to 5ppm level.
A 30-minute run at that level resulted in
- 72% reduction in airborne bacteria at a 0.5ppm level
- 93% reduction at 2.5ppm
- 90% reduction after 30 mins at a 5ppm level, showing there isn't a lot of benefit past a certain point, partly because in the real world most rooms cannot be fully sealed during the process.
That's not a 30-minute run time on the machine. That's keeping the machine on for 30 minutes after the concentration reaches a given level and then waiting until it falls to a safe level to enter the room.
Viruses are supposedly more susceptible to ozone than bacteria, so the idea is that the virus reduction would be the same or better.
https://www.ozonetech.com/sites/default/files2/pdf/Ozone_disinfection_of_SARS_Contaminated_Areas.pdfSome studies have found that even at concentrations of 100ppm to 1000ppm, it is difficult to get significant biocidal action, especially on porous materials. Unfortunately, on the abstract of that study seems to be available for free
https://www.tandfonline.com/doi/abs/10.1080/01919510903043772
