What floor are you currently living on? Your figure of 100 meters above ground would normally mean a building of around 25 floors or more.
One expert, Dr. Arvind Kumar of the Lung Care Foundation, has said: "air pollution is generally lower on higher floors in a high-rise building because the major sources of air pollution in large cities (that have high-rise buildings) are vehicular traffic emissions and construction debris. However, higher floors can also be more exposed to outdoor air pollution from other sources, such as industrial areas or open burning." (The bold font on the word "burning" is mine, not Dr. Kumar's, since burning of crops seems to be a major cause of air pollution in most of Thailand.)
We use air purifiers continuously during the several months of bad air here in Pattaya. We are on the 16th floor. On the Xiaomi purifier next to my desk, the PM 2.5 reading right now is 1, while outside the current reading is 34.4 µg/m³(according to IQAir at 13:30, January 20). In the past, the air purifier filters lasted about 12 or 13 months, but recently, we have had to change them in only 11 months.
We turn off the purifiers in the dining/sitting room at night and use purifiers in our bedrooms. When opening again in the dining/sitting room in the morning, the PM2.5 reading has shown as high as 24 when we first open the 2 purifiers there. (Note that sometimes during cooking, the reading can be much higher than that -- say 50 or over for a few minutes.)
As others have stated on this site, we are very happy with the performance of our Xiaomi purifiers.