Air purifiers can be effective in removing allergens and irritants from the air. These allergens and irritants can be broken into two broad categories:
- Particulate matter – particles include pollen, pet dander, mould spores and dust mite allergens.
- Smoke, gasses and volatile organic compounds (VOCs) – including pollution and fragrances.
There are a number of different technologies utilised, but most purifiers include an electrically powered machine that sucks air in, removes or neutralises contaminants and emits cleaner air:
- Particulate filters are designed to capture particles above a defined size – High-efficiency particulate air (HEPA) filters are frequently found in air purifiers. H13 HEPA filters filter 99.75% of particles above 0.3 micrometres (a micrometre is one-thousandth of a millimetre). Generally, the smaller the particle, the longer it may remain airborne. Larger particles like dust mite faecal matter and pollen will fall quickly to the ground in still air (pollen can remain airborne outside because of the wind and convection currents). Some machines claim to have HEPA-type filters – these do not work as efficiently. The best HEPA filters used in purifiers are designated E12, H13 or H14.
- Activated carbon filters absorb gasses and volatile chemicals (but not larger particles).
- Some air purifiers use heat, electron discharge or ultra violet light to neutralise contaminants. These techniques are proven, but in order to be effective, bacteria and other pathogens need to be exposed for sufficient time (at sufficient power) – sometimes attributes like UV light are more about marketing than effectiveness.
- Ioniser technology charges a collector plate in the machine which electrostatically attracts charged particles in the air. Machines that simply emit negatively charges ions are not purifiers and there is little evidence to suggest any positive impact for respiratory conditions.
- Some purifiers emit ozone. These should be avoided unless the zone emission concentration limit does not exceed 0.050 parts per million.
- Fragrances do nothing to purify the air and some people are allergic to some fragrances.
- Machines that increase humidity should only be used in dry climates – higher humidity promotes mould growth and dust mites.
Effectiveness of air purifiers will depend on:
- The amount of air processed.
- The type of operation (ability to remove contaminants).
- Quality of construction.
- Size, quality and age of filters.
- Maintenance of the machine.
- Size of the room or area and the rate of air exchange (ie – a purifier will have much less benefit in a large room with frequently opened doors and windows than a smaller better sealed room).
The saying “you get what you pay for” is likely to be true with air purifiers – cheaper machines will be less likely to process as much air effectively as larger better-quality machines.
The materials used in the machine may also be relevant for some highly sensitive people.
Sensitive Choice approved air purifiers can be found here.