And without an expensive reference device it’s hard to tell if it’s right aside from „opened window and it dropped“
The only thing I would disagree with is the recommendation of the uHoo monitor. There are many people not happy with the accuracy and AQSpec, a US EPA test center, also tested the unit with pretty bad results.
See http://www.aqmd.gov/docs/default-source/aq-spec/field-evalua...
Also ozone machines, when used properly and safely (no occupants), can sometimes help to speed up the offgassing process. If you're interested in doing this, please read up on it so you don't do it wrong or dangerously. It can also in some cases cause new, worse VOC's to form, so...user beware.
I would add that heated clothing is fantastic. You cant heat the house to 30C and if it gets to warm you cant easily lower the temperature.
No comment other than without the public meters, I wouldn't have noticed. I have no idea what outdoor Tokyo is, I assume 400 but are cities different?
Can't understand what you don't interact with.
(Picture of their meter (display?)) - https://imgur.com/a/PfjNgjO