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Do you really need an air purifiers? How to choose one with safety and performance - CHOICE # 385

  • 2008.11.14

Are you taking the problem of your indoor air quality seriously?

With air purifiers coming in different sizes and features these days, consumers have a real baffling choice especially with their safety and performance.

Help is now at hand. The Consumer Council has sampled 10 models of air purifier in a test to evaluate how safe and good a task it could perform in indoor air cleaning.

Air purifiers clean the air by trapping or adhering airborne particles as they are drawn in through filtering mechanisms by a fan.

But before you consider buying an air purifier, the Council has this advice to you: Do not rely solely on air purifiers. In other words, air purifiers alone may provide some relief but they are not the total solution.

Indeed, you probably needn't pay for clean air if you apply some simple basic steps in household hygiene and disease prevention - for instance, by the elimination or reduction of pollution sources, and better ventilation to increase air flow.

After all, though many air purifiers promote claims of removing bacteria, virus, dust mite allergen or mould, medical opinions have observed that as these devices are designed for domestic use, they may not be able to alleviate all of these impurities.

Besides, air purifiers featuring negative ions might generate ozone (which is regarded as an air pollutant harmful to health; but fortunately, all samples in the test were lower than the limit on ozone concentration level), and some samples use ultraviolet (UV) lamps (which consumers should switch off before maintenance to avoid risk of radiation exposure).

In the test were compared the safety and performance of 10 models, ranging in price from $700 to $4,000, in accordance with the International Electro-technical Commission (IEC) and Association of Household Appliance Manufacturer (AHAM) standards respectively. Highlights of the test include:

  • On performance, larger samples deliver clean air quicker than small ones. But larger models can be pricey.
  • Only 4 of the 10 test samples were supplied with claims on their Clean Air Delivery Rate (CADR). 2 were close to the actual CADR test data with less than 10% deviation; 1 was 20% lower; 1 not comparable due to the use of non-AHAM measurement. The Council recommends manufacturers to provide CADR information.
  • The size of the room is an important factor in choosing an air purifier. Based on AHAM formula, the majority of the models was found to have a lower maximum usable area than claimed. The deviations may be due to differences in test method and conditions.
  • The maximum usable area should be 1.5 times its CADR, according to AHAM. For instance, in the case of a 120 sq.ft. room, the CADR should not be less than 80 (80x1.5=120).
  • On safety, with due care, the samples were considered safe to use under normal operating conditions.
  • 3 samples were found to have plastic parts with inadequate flame retardant capability, i.e. some parts were ignitable by a glowing wire or a small flame without self-extinguishment. However, one of the samples was operated by a low voltage and was considered to satisfy the Electrical Products (Safety) Regulation.
  • All samples carried no warning as stipulated in the latest amendment of the international standard - the need to take care of children, elderly and disable people on using the appliances. The agents concerned have undertaken to incorporate the marking in the users' instruction.
  • On noise, as air purifiers use a fan to draw air through a filter, noise levels can increase with fan speed.
  • Overall, on the basis of clean air delivery capacity (50%), safety (45%) and noise level (5%), the samples were rated on a 5-star scale. 3 samples scored 4.5 stars, 3 samples 4, 3 samples 3.5, and 1 sample only 3.

Consumers are also reminded of the importance of maintenance of the filter, which needs to be cleaned or changed regularly or it will clog up and become less efficient.

Inefficient filtering and/or leakage around the filter would also release the trapped airborne impurities back into the air.

It is therefore advisable for users to check with the agents the available of a particular filter before it fails to function.

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