I recently bought an air purifier for my house and it's constantly red when used in living room that has outside windows. In other words, air quality around my house is constantly bad. By the end i moved it to an isolated room where at least we can enjoy clean air there.

Maybe consider a boxfan+furnace filter for the living room - if air quality is always bad you don't really need the sensor switching

What city? It is too generic to say "Southeast Asia". Most of it is rural. And what is meant by "unhealthy"? What measurements? I cannot believe that 90% of days were unhealthy. Why? Rainy season is never polluted -- I know from experience in Hongkong and Singapore. Once a day or more, you get a huge downpour that takes most pollution out of the air. (This is partly why Seattle fairs very well in clean air measurements... it rains so damn much. Scottish cities, too.)

Seattle's air pollution quality is so low because there's a vast ocean separating the Seattleites from the manufacturing that supplies it with new phones, appliances, furniture, clothing, building materials and just about everything from the source of the pollution.

Rain is nice, but that has very little to do with it.

The growth in moat of these countries is up so much they cant burn enough coal to keep from brown outs.

Outsourced pollution.

If you need data, just peak at a global air pollution map. Dive into the historical metrics.