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Air purifiers de-mystified: How do you know which is right for you

What should you consider before buying an air purifier? What is a HEPA filter? We take you through what you need to know before purchasing an air purifier.

With most of us currently spending more time indoors, the quality of air that we breathe in our homes has become a hot topic. Many homeowners are starting to realise the benefits of going one step further and investing in a home air purifier. A plethora of choices and confusing descriptions can make it difficult to determine the best choice, but it doesn’t need to be that way, our short guide to air purifiers and the common terminology can help.

What do air purifiers do?

Air purifiers clean and recirculate the air, improving indoor air quality by refreshing stale air, reducing odours and capturing airborne contaminants including pollutants, dust and dirt, germs and viruses.

Why do you need one?

Sometimes referred to as ‘toxic boxes’, homes may contain as much as five times the level of pollutants as the air outside. Our homes are routinely exposed to multiple sources of pollutants from airborne dust or dirt particles, which if small enough can enter the lungs or bloodstream through to bacteria, germs and viruses which can piggyback on other airborne particles.

Older, poorly ventilated homes can be subject to damp and condensation, encouraging mould and fungi to grow which may trigger asthma attacks, while exhaust and fuel emission in high traffic areas can enter via windows. Additionally, chemicals in household cleaners and substances in furniture or building materials can release gases at room temperature in the form of Volatile Organic Compounds (VOCs) which may result in nausea, breathlessness and impaired cognitive function.

How do air purifiers work?

Air purifiers use fans to suck in air from the atmosphere and release it again after treatment. The air is passed through one or more filters which traps particles, pathogens, allergens and other pollutants to maintain healthy air circulation.


How to select the right purifier for your needs:

Everyone’s needs and budgets are different but, in all cases, you will need to consider the following:

  • Room Size
  • Type
  • Noise
  • Energy Consumption

Room size/floor area

As air purifiers are most effective when they are compatible with the room, the room size will determine the type of air purifier you need. On average, bedrooms are between 23 to 33 square metres in size.

Always look at the Clean Air Delivery Rate (CADR) ratings which indicate the speed at which the purifier can. CADR is measured in cubic feet per minute (CFM). For example, an air purifier with 400 CFM will purify the air in a 37 square metre room much faster than an air purifier with 300 CFM. Air purifiers with CADR 300 to 400 should be perfect for average-sized rooms.


You will also need to decide which air purifier is the best at filtering out pollutants specific to your home or health needs.  For example, do you have asthma or allergy sufferers in the house? If so, you need to consider filters that can remove dust, pollen, dust mites and other triggers. Or you may be a pet owner or smoker in which case an odour removing filter could be an excellent feature.

With the current focus on Covid-19, a filter that can help to remove bacteria and viruses may be a priority. HEPA filters are one of the main filters to check out. HEPA filters combined with a carbon filter can be an effective combination in removing odours and gases, while trapping viruses and bacteria.


The noise level of an air purifier can depend on the operational settings, but most air purifiers can produce noise ranging from 35 to 70 decibels. To avoid sleep disruptions, opt for air purifiers which are effective when set to a lower operational setting and therefore reduced noise level.

For bedrooms you may also want to check if the unit has a night-time setting.

Energy consumption

Running costs may also be a key factor in your decision, making. Some models will switch to standby when sensors no longer detect airborne pollutants.

For example, Daikin’s air purifiers use renewable energy, combined with innovative technology to deliver higher energy efficiency, with ‘eco’ modes to cut consumption still further.


If you have a good budget, optional extras can include display dimming and shut-off and programmable timers which offer greater flexibility and ease of use. Remote controls with smart functions allow you to operate your air purifier from anywhere via a downloadable app on your phone and some models even incorporate voice control using Alexa.

To find out how to improve your indoor air quality click here.

Common air purifier features explained

Finding the right air purifier depends greatly on what you what kind of indoor air issues you would like it tackle. We compiled a list of the most common air purifier features you will come across in order to help you find the one that is best suited to your needs.

Clean Air Delivery Rate - CADR

Measures how effective a device is at filtering various particles in a specific room size. Calculated in cubic feet per minute. The higher the CADR number, the more particles are removed and the larger the room the unit can expected to clean quickly.

Air Change Per Hour - ACH

The number of times per hour the entire volume of air in the room gets filtered. Frequent filtration reduces the risk of left-over pathogens. Most air purifiers take between thirty minutes and two hours to clean a room.

Airborne Particulate

Substances small enough to be suspended in the atmosphere as solid particles or liquid droplets. Dust, smoke and pollen particles are the most common pollutants.

Volatile Organic Compound - VOC

Gases released from constituent elements in cleaners and given off by furniture etc. Includes formaldehyde, benzene, chlorine, phthalates, ammonia.

HEPA filter

Short for high-efficiency particulate absorbing filter. An air filter consisting of interlaced glass fibres, capable of removing at least 99.97% of dust, pollen, mould, bacteria and any airborne particles with a size of 0.3 microns, the most penetrating particle size.

Flash Streamer

Daikin’s signature air-purification technology. Electrons are discharged which hit viruses, mould, bacteria, allergens and hazardous chemical substances, decomposing and fragmenting their surface proteins, which are then destroyed through oxidation. The discharge then breaks down into safe nitrogen, oxygen atoms and water molecules.

Titanium apatite filter

Removes airborne particles, capturing pet odour and tobacco smoke. It also deactivates harmful chemical substances to ensure a steady supply of clean air.

Silver Filter - Allergen and air purifying filter

The silver filter captures allergens such as pollen and dust mites. Thanks to its high quality and remarkable efficiency, replacement of the filter is unnecessary.

Activated Carbon filter

Effectively traps odours but unlike HEPA filters cannot capture viruses and bacteria.


UV rays used to kill germs floating in the air.

Plasma ioniser

Releases 25,000 ions per m3, which recombine with particles in the air to decompose fungi and allergens.


Coarse screening membrane - Designed to capture and remove large particles like dust and hair to avoid clogging the HEPA filter.

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