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Most bacteria vary in diameter from 0.5 to 1.0 micron and most viruses vary in diameter from 0.02 to 0.5 microns. Recognized viral strains such as SARS-CoV, MERS-CoV or Covid-19 have a particle size of 0.005 to 0.1 microns. Most often, they form accumulations with other larger particles (such as saliva or suspended matter) which increase their size up to 0.4 - 0.5 microns.

In order for an air cleaner to be effective in removing viruses and bacteria from the air, it must be able to remove or destroy small airborne particles in the size range of 0.1-1.0 micron.

What are the available solutions?

1. Air purifiers with True HEPA13 or medical-grade True HEPA 14 filters

A True HEPA H13 filter gets rid of at least 90% of the particles the size of virus-containing aerosols as it captures 99.97% of particles as small as 0.3 microns. A True HEPA H14 filter is 10x more efficient as it captures ultrafine particles as small as 0.1 microns.

An air purifier should be powerful enough to drag all of the air in the room through the filters a minimum of 6 times an hour (ACH) for it to be genuinely effective (equivalent to the air circulation recommended for a private hospital bed). To get around 6 air changes per hour in your room measuring between 11 and 20 m² you need an air purifier with a clean air delivery rate (CADR) in the range of 200-299 m³/h. CADR rating indicates how fast an air purifier can clean the air within a particular size room. It provides a way to compare air purifiers taking into account both airflow and a filter's efficiency.

2. Air ionisers or electrostatic air purifiers

Ionisers release negative ions into the air which collide with suspended ultra-fine particles such as viruses and bacteria and give them a charge. These charged particles bundle together and fall down on the ground and nearby surfaces, thereby disinfecting the air and stopping the transmission of infections.

The effectiveness of an air ioniser is dependent on the homeowner as the area surrounding the ioniser and the positively charged collector requires regular cleaning.

Air ionisers are fanless, use very little electricity, virtually silent, easy to move from room to room, don't create draughts or use filters, except for ones that include a positively charged collector.

Electrostatic air purifiers use a fan to speed things up and have a positively charged replaceable filter that attracts particles.

3. Air purifiers with Photocatalytic Oxidation (PCO) technology

Instead of capturing pollutants, viruses and bacteria, the PCO technology chemically “attacks” them breaking their bonds and degrading them. Pollutants are not collected inside an air purifier with the PCO technology but transformed into safe substances, thus removing the need for replaceable filters.