Jun 262013

The recent record-breaking haze levels have created a new, heightened awareness of the need for clean air in our homes. Indoor air pollution is one of the greatest environmental health risks we experience, so it could be worthwhile to explore this topic further. In this article, we will focus on particulate matter pollution, and tips on choosing the right air purifier to match your indoor spaces. While there are also technologies with germicidal and odor-removal functions, they are beyond the scope of this article.

So how exactly do we go about dealing with this issue? Well, it just so happens that the premier technology in removing particulate matter is actually a simple and straightforward mechanical filter. The high efficiency particulate air (HEPA) filter is certified to meet United States government standards for air particulate filtration. Such filters have been tested and certified to remove 99.97% of airborne particles that are 0.3 micrometres in size.

Unfortunately, the market has become confusing, with many claims of adherence to HEPA standards. We feel some clarification is in order.

“True HEPA” is a purely marketing term born out of necessity to distinguish HEPA-certified filters from other claimants. These filters have been certified to meet HEPA standards, and should have test results printed on them. You can be confident that “True HEPA” filters will remove 99.97% of 0.3-micron particulates from the air that passes through it.

“HEPA-like”, “99% HEPA” and “HEPA-type” filters may have similar structures and physical characteristics as true HEPA filters, but have notbeen tested in independent laboratories. As such, they do not satisfy HEPA requirements. Their performance could be as good as HEPA filtration, or they could be significantly inferior, but there is just no way of knowing how effective the one you just bought is.

The next decision you have to make is capacity. Air purifiers will generally have a rating to indicate the size of room (in square feet) that they are suitable for. That rating assumes a standard ceiling height of about 7 feet and one or two cycles per hour. All the air in the room will have gone through filtration each cycle. Thus, an air purifier rated at 150 square feet coverage, operating for one hour, would have completely processed the air in a room that is 150 square feet with a ceiling height of 7 feet. Some manufacturers do quote 5 or more cycles per hour, which would mean greater cleaning capacity even with the same coverage.


Most Housing Development Board (HDB) apartments will not have common rooms larger than 120 square feet, while typical private apartments might have rooms up to 200 square feet. The living rooms would be larger than that, of course. Matching air purifier area coverage to room size is generally quite straightforward, but there are a few things to take note of:

  1. Ceiling height. While HDB ceilings fit into the standard ceiling height, some private property may have high or even double-height ceilings. Such double height spaces will require a coverage rating that is double their square footage.
  2. Furniture. This can also affect air purifier efficiency. Although the effect is quite minor, you might want to get larger coverage if you have several pieces of large furniture.


Another consideration when choosing an air purifier is its acoustic signature. This is an indication of its operational noise level, and is usually measured in decibels (dB). However, there are no standard ways to measure this, so many variables come into play. For example, some manufacturers quote the dB figure in low power mode, while others use high power mode. How far away from the unit was the measurement taken? Even the measuring instrument can affect the number significantly.

Different manufacturers use different methods to measure acoustic signature, so it is hard to get any meaningful comparison from one brand to the next. Lower numbers don’t always mean absolutely quieter operation, so take note of that when buying a unit.

Once you have narrowed down your choice and are ready to make a purchase, please do note that purchasing locally is not the only option. Buying locally may be expensive, and you may not be able to find the model you want due to a poor selection of products. The Singapore market is small, and prices can be easily inflated.

One alternative is to shop online. Amazon for example has a good selection of Honeywell products such as:

Honeywell QuietCare 17000 - portable, true HEPA air purifier that covers up to 168 square feet at 6 cycles per hour

Honeywell Enviracaire 50250-S – true HEPA air purifier that covers up to 390 square feet at 5 cycles per hour

You might even be able to take advantage of their free shipping offer! Please note that each product may be available from multiple merchants, and not all will ship globally. Generally, items sold directly from Amazon will most likely ship to Singapore and be eligible for free shipping.

While shopping online can be convenient do take note that models meant for the United States market may be built for 120V power supplies. Such products will require a transformer to “step-down” (convert) our 240V power supply to 120V. Transformers are readily available here for under SGD50, just make sure that the power output (in watts) of the transformer is at least twice the wattage of the air purifier. This is because transformers often state their peak power output rating instead of sustained power output, while appliances are rated by their sustained power consumption. Thus, getting a higher-rated unit will lessen the chance of power trips and blown fuses. More reliable brands might not need such a large margin, however.

We hope that this beginners’ guide was useful to you, and wish you many clean-air days ahead. If you have an opinion or other insights to share, please leave a comment below or on our FacebookTwitter, and Google+ pages. Don’t forget to “like” to keep up with our latest content.


  No Responses to “Tackling the Haze at Home”

 Leave a Comment