The incident itself was: when we entered the room it smelled kind of strange, it's hard to describe. I dismissed it as "weird hotel room smell."

After 15 minutes, my asthma started to really get bad, even when using my puffer. Like, unable to breathe bad. We all developed a severe headache and dizziness. After another 15 minutes of searching, I found this small device in the room that was running on full blast.

Translating it with my phone, it described itself as an "anti-virus cleansing tool" or something. I aired out the room immediately, but ultimately we didn't feel comfortable staying there anymore and left. Quick phone research showed you should give 2 hours minimum before letting guests into the room, let alone have it running 24/7.

They refused to give us a refund. My general experience in Japan was that people will try to "smooth over" any problems, but IMO actually poisoning your guests isn't smoothable. I got the feeling this is just kind of the way this hotel operated; which is strange because it had generally good reviews.

I called my doctor later, but he said I probably should be fine; it's comparable to having chain smoked 20 cigarettes. More of a continuous long term risk than an acute risk. Not ideal for the younger family members obviously, but you also can't change the past.

After that incident, I was paranoid and on the lookout everywhere for these machines. I noticed that most elevators had "anti virus" ozone blasted in them. Stores and shops did too. I got pretty good at detecting the smell, and would look around for a sign on the wall advertising the "anti virus" features, usually in Japanese. I tried to hold my breathe or cover my mouth to prevent symptoms.

Every hotel room and airbnb had one of these machines; sometimes gigantic cabinet sized ones. Though apart from the incident, they were all switched off and hidden in a closet, so I was mostly ok with it.

I think it's to try and combat COVID-19 or something? But they just never took them down. From my research, they're actually completely useless for this purpose, but it probably feels better than doing nothing.