We may need an air purifier MORE when we are at home, inside a car, plane, restaurant, drinking bar or cinema than when we are out in the streets. Just because the air smells worse outside, does not necessarily mean it is more noxious. When we are in an outdoor environment, we are at least in a ventilated environment. Research has indeed confirmed that those inside home, vehicles - even with the windows closed and the air-conditioner on - are in a far more polluted environment than those in the streets.

In fact, the Environmental Protection Agency in the United States estimates that indoor air is two to five times as polluted as air on the other side of the window. What's more, we spend as much as 90% of our time indoors, so the risks to health may actually be greater coming from the pollution in our homes and offices than from the streets of Causeway Bay.

Closing all the doors and windows to keep out Hong Kong's dirty air does not help, and may even make things worse. And as an adjunctive measure, air purifiers can offer significant relief from indoor air pollution.

Home use air purifier offers effective protection against indoor air pollution but is limited to the area where it is installed. Wein Product Inc. - an American company based in California has invented Air Supply - the world's first portable, air purification system that is compact enough to be conveniently used in any indoor environment. It has had much subjective success with improving breathing and limiting pulmonary infections.