@luckytran There's also a reason why Helsinki specifically has been looking into this.

Namely because A WHOLE LOT of schools in Helsinki metropolitan area are mold-infested.

Many of these school buildings were designed as a temporary measure to provide schools for families that were moving into the city post-WW2 into 1990's.

However, the more permanent solution took too long, which meant that these buildings started showing their age and flaws, which in turn, caused air issues...