2015-01-26, 07:59
whey
"I feel sorry for people who are trying to do the best thing by buying an air purifier, because the marketing is not good," he says. "It is very hard to be a well-informed consumer, no matter how sophisticated you are. You are making an assumption that buying the most expensive thing will be the most effective solution. It may be the best because it may be more durable but the fact is that inside these machines, [the technology is] very simple. They have filters to take out different sized particles. Coarse particles like dust, medium particles like pollen and small particles like smoke. Ninety per cent of these air purifiers are the same inside. They've got a fan and two or three levels of filter material. Personally, I would advise people to look for a [brand] they recognise from their household appliances in a price range they can afford. Most importantly, remember air filtration systems only work if you have the right sized machine for the room and change the filter regularly. Otherwise they are pretty useless."
Westerdahl uses two second-hand air purifiers, which he bought for HK$500 each, in his apartment in Sham Shui Po.
"I have worked on pollution for 40 years and I am concerned enough about the air here to have two of them. You can make a difference with an air purifier in your home. I ran tests on the air purifier in my bedroom. Within 10 minutes of turning it on, the particle level reduced by about 95 per cent."
His advice is to research what sized particles the machine can remove: "The particles from diesel are 0.2 to 0.3 micrometers. In this city, that's the size particles you want to get rid of. They also happen to be the hardest to remove because of the physics of filtration. You want to check that whatever you buy specifies that it removes these very small particles."
For those who cannot afford an air-purifying machine, Westerdahl suggests putting filtration material, for example, 3M Filtrete, which you can buy in hardware stores, into the filters of your air conditioner.
"I ran a test in my own home by putting filtration material into my window air conditioner. After two weeks' use, the colour changed from white to black. The kind of pollution this is catching has a lot of carbon in it. It's diesel exhaust, a traffic-related pollutant. If the filter isn't catching this then your lungs will. You don't have to spend a fortune to make a difference."
Westerdahl uses two second-hand air purifiers, which he bought for HK$500 each, in his apartment in Sham Shui Po.
"I have worked on pollution for 40 years and I am concerned enough about the air here to have two of them. You can make a difference with an air purifier in your home. I ran tests on the air purifier in my bedroom. Within 10 minutes of turning it on, the particle level reduced by about 95 per cent."
His advice is to research what sized particles the machine can remove: "The particles from diesel are 0.2 to 0.3 micrometers. In this city, that's the size particles you want to get rid of. They also happen to be the hardest to remove because of the physics of filtration. You want to check that whatever you buy specifies that it removes these very small particles."
For those who cannot afford an air-purifying machine, Westerdahl suggests putting filtration material, for example, 3M Filtrete, which you can buy in hardware stores, into the filters of your air conditioner.
"I ran a test in my own home by putting filtration material into my window air conditioner. After two weeks' use, the colour changed from white to black. The kind of pollution this is catching has a lot of carbon in it. It's diesel exhaust, a traffic-related pollutant. If the filter isn't catching this then your lungs will. You don't have to spend a fortune to make a difference."