Do Air Purifiers Really Work Or Is It A Scam?

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How do air purifiers work? 

While all air purifiers have the same end goal — to get rid of air pollutants, they may operate differently. This is where you should take careful note of since not all air purifiers are created equal.

Most air purifiers rely on 3 main processes to achieve clean air — by releasing negative ions, killing pollutants with ultraviolet rays, and/or using a HEPA filter to trap pollutants. 

Which air purifier is the best?

What is a negative ioniser?

Pros: Release of anions which are beneficial to health
Cons: Accumulation of particulate matters at home and the risk of ozone emission

Negative ionisers are also known as ionic filters and ionic air purifiers. Instead of removing airborne pollutants, these air purifiers release negatively-charged ions to attract positively-charged ions that are harmful. 

anions natural landscape
Anions are abundant in natural landscapes

As a result, these neutralised ions are too heavy to remain airborne and are stuck on nearby surfaces instead. Having a negative ioniser can be a double-edged sword since these neutralised articles linger instead of getting filtered. On the flip side, an abundance of negatively-charged ions have plenty of healthful effects — enhanced immunity, improved sleep quality, and lesser allergy triggers.

Another side effect is ozone emission. According to the EPA (United States Environmental Protection Agency), breathing in ozone may irritate your throat and lungs, causing shortness of breaths, and coughs. 

What is a UV light air purifier?

air purifier air cleaner

Pros: Remove germs, bacteria, and viruses.
Cons: Does not filter dust and common allergens 

UV air purifiers, or sterilisation lamps, rely on ultraviolet rays (UV-C light) to kill microorganisms and pathogens such as mould, bacteria, and viruses. If you live in a tropical and humid environment or are allergic to mould, a UV air purifier will be the perfect fit.

However, UV air purifiers cannot remove air pollutants such as dust and common allergens. Most air cleaning brands then combine both UV light with additional filters such as a HEPA filter or activated carbon — which brings us to the next point.

What is a HEPA filter?

air purifier air cleaner

Pros: Easily remove pesky irritants that even UV rays can’t
Cons: Require regular filter replacement and does not remove odours.

By far one of the most common and reliable methods to attain clean air, a HEPA (High-Efficiency Particulate Air) filter removes 99.97% of air pollutants of up to 0.3 microns. In other words, fine particles such as dust mites, pollen, and even viruses are removed. Doctors recommend patients with allergies and asthma to keep their homes clean with the help of such air purifiers as well.

To maintain the optimal filtering efficacy, however, homeowners should regularly wash and replace HEPA filters. This can come at an extra cost of up to $200 for as short as once every 3 months to a year. 

activated carbon
Activated carbon is also known as activated charcoal

Another common drawback HEPA filters have is the inability to remove odour. From secondhand cigarette smoke, the stench of Mao Shan Wang durians to paint odours, a layer of activated carbon will do the trick instead. These are adsorbent pores used for trapping gas molecules. 

What do HEPA filters in air purifiers filter?

HEPA filters are made of interlaced glass fibres and remove fine pollutants via 3 different ways – direct impact, interception, and diffusion
Image adapted from
Direct impactHuge particles collide and stick to fibres.
InterceptionParticles flow with the airstream and are trapped by fibres.
Diffusion According to Brownian motion, small particles zig-zag and crash onto each other before getting stuck onto a fibre. 

According to a study by NASA, viral particles, like the coronavirus, may be smaller than 0.3 microns but a True HEPA filter can easily filter it out via interception and diffusion – the last stage of the filtering process.

Since tiny particles tend to travel randomly, they are more likely to hit onto a fibre as a result. As such, HEPA filters are capable of capturing the smallest airborne particles at a near 100% efficacy.

You can check out the graph by NASA here:

NASA hepa filter process
Image credit: NASA

Given its impressive track record, most air cleaning brands now include HEPA filters in their air purifiers. 

Can HEPA filters in air purifiers help with allergies and asthma?

air purifier air cleaner

Homeowners suffering from asthma or allergies can find comfort in air purifiers with HEPA filters. However, this does not mean that HEPA filters are foolproof replacements for medicine or other proven methods.

In reality, the effectiveness of an air purifier with HEPA filters may vary as compared to in controlled settings. There are plenty of external factors such as the condition of the filters, how much space can your air purifier filter, downright to the possible emergence of new particles indoors and how serious your condition is. 

While there is no substantial medical proof that air purifiers with HEPA filters can maintain the same efficacy in the real world, plenty of patients showed lower episodes of allergic triggers in a study conducted in 2018

What other indicators should I look out for in an air purifier? 

Aside from ensuring that your air cleaner contains a certified HEPA filter, here are other things you can take note in your quest for clean, breathable air:

1. What is CADR (Clean Air Delivery Rate)? 

dust smoke pollen

CADR is a reliable indicator by the AHAM (Association of Home Appliance Manufacturers) to help consumers identify better-working air cleaners in terms of 3 metrics dust, smoke, and pollen. It measures how effective an air purifier produces a specific volume of clean air. 

As such, the higher the CADR, the better the filtering efficacy. Here’s the highest value an air purifier can score for each category of pollutants:


According to AHAM, an effective air purifier should score at least two-thirds of the room’s area. For example, a 2-room HDB flat in Singapore is typically 484 square feet. Assuming a homeowner wants to place an air purifier in the living room (147 square feet), the CDAC score should be two-thirds of the size of the living room — a score of 98 at the minimum. 


147 x ⅔ = 98

Note that it is not mandatory for air purifiers to be tested for CADR. Instead, you can rely on other indicators. 

2. What is GB certification?

In contrast to AHAM, an American standard, there are also certificates recognised nationwide in China. The GB (GuoBiao) standards are headed by the Standardization Administration of the People’s Republic of China (SAC). 

All domestic and international products in China must comply with the GB standards for ‘the protection of human health, personal property, and safety’.

3. What is ACH (Air Changes Per Hour)?

air cleaner at home

ACH (or ACPH) is a precise measurement of how fast air is filtered completely in a fixed space in just one hour. The higher the ACH, the more effective an air purifier is. You will need the results of your air purifier’s CADR and room dimensions. 

Simply key in the values using this calculator to get your ACH.

Note that there is no official recommendation of a desired rate of ACH. However, a study by the EPA has shown that a value of 0.35 is optimal at home. 

What other ways to improve air quality at home?

house plants

Doubtless to say, getting an air purifier isn’t the only proven alternative to breathing in clean air. Regular maintenance paired with frequent home cleaning make significant differences as well:

  • Avoid introducing new pollutants indoors such as smoking at home or using toxic cleaning products.
  • Avoid indoor plants as these may be hotspots for mould.
  • Ventilate your rooms regularly to allow the circulation of fresh air.
  • Invest in HEPA-certified vacuums, especially if you have pets around to clear pet dander.
  • Switch on your kitchen hood to rid the air of smoke and grease.

Which air purifier is the best in Singapore?

With plenty of air cleaning brands to choose from, we put together a comparison table to fast track your decision process. Make sure to keep in tabs of the type of features and services available.

comparing air purifiers

The Cosmo Prime® Air Purifier is ranked first in Singapore for good reason. The German design comes with an extensive list of functions which even includes a layer of activated carbon to keep your room stench-free.

Here are 6 more reasons why Cosmo is Singapore’s top air purifier here.

Or you can add our Cosmo Prime Air Purifier to cart directly here.

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