There are almost no UK industry standards against which to measure and judge air cleaners, so sellers can make claims that are actually quite dubious. Here are some things to be aware of when buying your air cleaner.

Statistics.

These are banded about with abandon. They can appear impressive but consider what they actually mean. For example, an air cleaner might have a claimed efficiency of 99.99%. But question; 99.99% of what exactly, what size particles, and on what airflow? It is easy to claim that more or less any air cleaner can have an almost 100% efficiency given the right size particle challenge and a very low airflow. Also beware machines that describe themselves as having HEPA filters. In the filter industry HEPAs come in a variety of grades, which are testable against any one of several industry standards. It is easy to make a claim of having a air cleaner with HEPA filtration when test airflow is much smaller than would be the case for a official test.

Airflow.

Airflow through an air cleaner means two things. Firstly, it gives rise to ‘air changes’ in a room. This means, for instance, if a room has a volume of 60m3, then a air cleaner that has an air flow of 360m3/hr will process the air in the room 6 times (air changes). Generally speaking the higher the airflow the quicker the unit will filter the air in a room and return it to a clean state when something happens like an influx of dirty air from an open door. Generally speaking the more often the air is passed through an air cleaner the cleaner the air will be maintained. A unit with a HEPA (high efficiency particle arrestance) filter and a low airflow could in fact be less effective than a unit with a lower grade of filter and a higher airflow. Air flow also gives rise to sound. Forced air movement through an air cleaner is impossible without generating sound. The more air you move, the more noise you get.

The performance of plasma and ozone based systems cannot be easily compared on the basis of air flow. Certainly it is a mistake to compare the airflow of a plasma or ozone system with a filter based system.

Performance

A system based on good quality filters will inevitably be better at particulate removal that systems based on ozone or UV, although generally they will be more expensive. Systems based on ozone and/or UV are generally designed to provide air which is free of viruses, smells, VOCs, bacteria, spores, chemicals etc. and will do this with variable degrees of effectiveness. The important thing here is to choose and use an air purifier that is suited to the size of room. Too large an air purifier and there is a risk of ozone build up - too small and the unit will struggle to be effective. Systems based on good filters will be more expensive, as they tend to be more robustly constructed and have better fans.

Quality

The old adage you pay for what you get is as true for air cleaners as for any other item. More expensive air cleaners, will typically have better and larger filters (hold more dust), will have better quality fans (better bearings, heavier motors etc.) have stronger bodywork parts. In other words they are designed to do a job and last.

Features

Often when you look at the various options on cleaners you will see a dazzling array of features and air cleaning 'hype' words. Sometimes the features are crammed into the air cleaner just to get ticks in potential buyer's 'mental check boxes', and are designed with economy in mind rather than performance. Lots of impressive filter stages and features may impress at first glance but each stage may be so under engineered so as to be useless.

Ozone

Some companies will go out of their way to give air purifiers that produce ozone a bad press. This is not a black and white issue, and buyers should understand some background to these potentially misleading assertions. Ozone is a powerful oxidising gas, which can be produced in harmful high concentration by ozone generators. These devices make ozone using electrical discharge and can easily generate ozone levels well above the laid down safety guidelines. Units that make ozone by ultra violet light based purification usually produce ozone at safe low concentration and as part of a 'photoplasma' which also contains oxygen singlets O, and hydroxyls OH. Provided that these type of purifiers are used in accordance with the manufacturers recommendations, the ozone concentration in the enclosed area will always be below 0.04ppm, which is far lower than the safety thresholds set by the Health and Safety Executive.

Our Descriptions

In our descriptions of the various air cleaners and purifiers that are offered on this website, we have reproduced, where appropriate, the claims of the makers of the various machines. Where claims appear 'over the top' to us as air purity specialists, we either omit to reproduce them here or tone them down a bit. (eg. if claimed to be a HEPA, we would probably say a high efficiency filter). The claims that are stated here are believed to be credible, however, not are not proven in any industry wide benchmark test standard. It is this approach that makes us distinctly different from other sellers of this type of equipment.

Clean Air Delivery Rate (CADR)

We have stated above that in the UK there is no recognized industry standard by which different portable air cleaners can be compared, however in the USA they have a standard developed by the Association of Home Appliance Manufacturers (AHAM). That standard has a method which generates a series of CADR values (Tobacco smoke CADR, Dust CADR, & Pollen CADR) for a tested air cleaner. These values are totaled to provide a combined CADR. The idea is that the CADR can help consumers choose a suitable air cleaner for their application by comparing  the various air cleaners with a CADR value that is sufficient for their application. If a group of air cleaners then meets that requirement then the consumers choice is then a matter of features, aesthetics, and budget.  At Adremit (www.puravent.co.uk) we like the idea and are supportive to its its use in the UK market.

The Association of Home Appliance Manufacturers (AHAM), recommend that you should select an air cleaner that has a tobacco smoke CADR of at least 2/3 of the room's area, thus, a 10' x 12' room -120 square feet - would require an air cleaner with a tobacco smoke CADR of at least 80. If your room size is smaller, the unit will simply clean the air more often or faster. If you have ceilings higher than 8', you'll want an air cleaner rated for a larger room.

Thus far the only units that we sell that have a CADR value are the Filtrete air cleaners from 3M