Prince, bear in mind that Sunday, Monday and today are not the norm, they are as good as it gets, and yes if it was like that all the time that would be fine. But the facts are that more than a 1/3 of the year is below 8Ks viz and last week there were 2 days that exceeded 1,000,000PMs ( 60,000 being the WHO limit ). Also, the WHO estimate that exercising outdoors in Hong Kong is safe for around 1 month/year.
No filter will get rid of all the nasties but do you really want you and/or your family to be breathing the PMs PLUS the organic materials ?
Unfortunately, with summer coming and the mostly clear days, everyone soon forgets that they will be choking again in less than 6 months, and it is statisically getting worse each year .