How Purifiers Work

By far the most effective technique for removing the most dangerous pollutants from the air is the use of an air purifier combining a ‘HEPA’ particulate filter and an ‘activated carbon gas filter.

A HEPA filter (‘High Efficiency Particulate Air’) traps nearly all of the most dangerous particles in the air passing through it.  It consists of a fine mesh-like material combining strands and gaps of a particular size designed to ensure particles are either two large to pass through, or small enough to be attracted to the surface of the mesh.  A couple of centimetres of thickness is the norm, creating a balance between a longer lifetime (not being clogged up) and allowing air to flow through.

HEPA filters are now common in higher-end purifiers.  Filters marketed as ‘HEPA-like’ do not meet the same standards.

‘Activated carbon’ is a type of charcoal, specially heat-treated, often with other chemicals, such that, when combined into a filter, causes polluting gases to stick to its surface by molecular attraction forces.  Unlike with HEPA filters there are no common standards and care needs to be taken to evaluate the true merits of any carbon filter. Many lower-end purifiers are marketed as containing activated carbon, so what should you look for?

Here, quantity matters.  Most cheaper, and even many expensive purifiers contain just a few grams of carbon, if any at all, often sprayed onto a screen or incorporated into the HEPA filter. But the less carbon, the quicker it becomes saturated with gases and ceases to function.  In the case of carbon screens this can be a matter of a few weeks at best.  A truly effective indoor purifier will contain several kilograms or more of carbon and as much as 1kg even in a vehicle model.

How this carbon is pre-treated also has a considerable effect on its ability to trap specific gases – and affects the price.

Today you can buy purifiers covered in useful features, from timers, speed settings and filter change alerts to remote controls, automatic sensors and linked apps on your phone.  However, when considering which will work best for you, do not lose sight of the most important features – the filters.

At Plain Air we understand that choosing the right purifiers can be a minefield.  Grandiose marketing claims, dodgy science and poor products are rife.  We can advise you based upon your individual circumstances and budget, and will never recommend any product that we aren’t convinced will improve your and your family’s health.

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