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What to look for when choosing an indoor air purifier

Boy sitting next to air purifierSome of the clear beneficiaries of China’s now infamous bad air are manufacturers of air purifiers. Predictably, the decrease in China’s air quality has seen an inversely proportional increase in the number of these products hitting the market. So how can you decide which one to choose? David Noble, International PR Manager for Blueair explains how to separate the wheat from the chaff.

Although the air quality in China may not have actually worsened over the past year, the frenzied media attention that the subject has drawn makes it seem like it has: it has also significantly raised awareness on this issue among the general public. Understandably, the main media focus has been on the health consequences of living with air that is heavily polluted by dust, chemicals and other particles. This has led to an increased interest in creating safer indoor environments, at home and in the workplace. One of the options available to concerned citizens is the use of indoor air purifiers.

Yet, anyone worried about their indoor air quality will find themselves faced with a staggering choice of air purifiers from all over the world, with new brands appearing almost weekly. And, of course, all of them claim to do the job of removing airborne contaminants that can spark allergies, worsen respiratory diseases, cause headaches and leave odours.

But not all air cleaners live up to the claims of their manufacturers. Some electric air purifiers even create ozone, which can lower lung function and cause health problems such as chest pain, shortness of breath and throat irritation.

Purifying technology
Anyone looking to purchase an air purifier should prioritise performance above all else. The key factors affecting the performance of such devices are efficiency and airflow, and the way they work together to remove pollutants bombarding our indoor air.

Most air purifiers will remove particles and a few will removes gases. Some will remove both using either ‘mechanical’ filtration technology or ‘electronic’ cleaning technologies. Mechanical air cleaners involve drawing air into a unit and passing it through a fibre or other filter with different sized pores to trap particles. An electric air cleaner will use either ozone generators, electrostatic precipitators (ESPs) or ionizers. Some manufacturers have developed technology that combines electrostatic and mechanical filtration. This can produce a capture rate of up to 99.97 per cent of airborne particles down to 0.1 micron in size.

Locking in particles at different stages ensures they are never released back into a home or office environment, even when filters are heavily loaded. The early layers capture larger particles like pollen and dust, while later filter layers capture smaller bacteria and exhaust particles.

Separating the good from the bad
Scientific evidence is still being gathered about the health impact of polluted indoor air. But with such an overwhelming amount of information, how can anyone make an informed choice?

One of the more credible standards for comparing the performance of air purifiers is the one developed by the one-hundred-year young Association of Home Appliance Manufacturers (AHAM), which seeks to provide consumers a level playing field to make informed decisions about the appliances they are evaluating prior to a purchase. The AHAM has developed a system for measuring the efficiency of air purifiers called the Clean Air Delivery Rate or CADR.

The CADR indicates the volume of filtered air delivered by an indoor air cleaner. Anyone looking to potentially purchase an air purifier should find and read the AHAM label on its packaging, which lists three CADR numbers ─ one for tobacco smoke, one for pollen and one for dust. The higher the tobacco smoke, pollen and dust count, the faster the unit filters the air. Devices with similar CADR numbers will have a similar level of efficiency.

The AHAM recommendations state that anyone in the market for an air cleaner should first ensure that the room size on the label matches the intended room size in which the device is to be used. It is then advisable to compare the CADR number of various models.

Indoor air cleaners produced by manufacturers that participate in the AHAM programme are certified and verified by an independent laboratory, which should provide some assurance that the product will perform according to the manufacturer’s product claims.

But, do they work?
A first-of-its-kind study was undertaken by Fudan University, Shanghai, in late 2015. Tests carried out on a group of young, healthy adults found that the use of efficient indoor air purification systems had clear health benefits for both heart and lung function. The Fudan study comprised a randomised, double-blind crossover trial among healthy college students divided into two groups that alternated the use of genuine and fake air purifiers for a period of 48 hours.

According to the study—recently published in the Journal of the American College of Cardiology—the test “demonstrated clear cardiopulmonary benefits of indoor air purification among young, healthy adults in a Chinese city with severe ambient particulate air pollution”. The authors added that one could expect even larger heart and lung benefits of air purification among particularly vulnerable people such as the young or elderly.

The study also rejected the notion that people could escape indoors to avoid outdoor pollution. Researchers found that while closing doors and windows barely reduced the concentration of PM 2.5, the use of an air purifier “efficiently reduced” the amount of fine particles in the indoor air resulting in improved heart and lung function.

Energy efficiency matters, too
For maximum performance an air purifier should run twenty-four hours a day. Research has shown that traditional room air purifiers can use approximately 550 kWh a year when running continuously, which is more energy than some modern refrigerators. This will naturally have an impact on the environment, so this is something that must be taken into consideration. When purchasing an air purifying device, it is therefore worthwhile ensuring that it is energy certified by a credible standards agency. Given that one of the main causes of air pollution in China is coal-powered electricity generation, purchasing an air purifier that is not energy efficient would be something of a self-defeating measure.

Blueair is a Swedish air purifying company formed in 1996 that today sells in over 60 countries worldwide.