Glueball,
so what your saying is only go outside if you are wearing a protective mask that can filter down to micron level? What about when the children are in school, at the park, out swimming, shopping, bike riding, horse riding, living...... Sorry to be the cynic, but if you live in HKG there's no way of avoiding it. Apart from living in a hermetically sealed clean room with an air supply from Fiji perhaps?