Air filters and purifiers

Air purifiers for allergies are a huge subject of interest and discussion for those with environmental and chemical allergies, partly because air cleaners and treatment systems are usually expensive and those with allergies need to give careful consideration before they purchase.

Considerations include noise levels, functionality, effectiveness, and energy efficiency. To some extent, these issues come down to personal circumstances and preference — for instance, how much you’re willing to spend, and the level of ‘intrusion’ (audio / spatial) you’re prepared to have in your room or home. 

However, my aim here is not to address these personal issues, but to instead look at which product you should choose for which allergy or allergies. 

 

Do you know your allergens?

This is key. Are you sure you know what you are — and are not — allergic to? 

We can take food out of the equation — not because food particles can’t be aerosolised (they can), but because you’re unlikely to have them in the home to start with.

That leaves two kinds — ‘living’ allergens, and chemical allergens.

Living or organic allergens include pet dander, mold spores, pollen grains and dust mite. These tend to be diagnosed through personal history, experience, blood tests and/or skin prick tests (SPTs), for instance.

IQAir MultiGas GC

Chemical allergens and irritants include cigarette smoke toxins, aldehydes such as formaldehyde, isothiazolinones such as methylisothiazolinone, and fragrance compounds such as limonene and linalool — often these are grouped together and described as VOCs (volatile organic compounds). Allergies to some irritant chemicals are diagnosable via patch testing, particularly if they are used as ingredients in cosmetics or household detergents.

 

Which filter?

The first thing to say about filters or purifiers is that their manufacturers don’t always make specific promises about effectiveness in tackling particular named chemicals. They are very good at quoting percentage success in removing particulates (typically high into the 99%+ range), plus the room size in which they can work optimally, as well as the minimum size of the particulates filtrable. ‘You get what you pay for’ does apply to some degree, but it’s important not to worry too much about such figures when they are very high — there’s very little difference between a machine operating at 99.9% and one at 99.7% capability, say, so this should not be a decision to distract you from the main goal of choosing appropriately to your allergies. 

 

1/ HEPA / HEPA-type filters

HEPA stands for high efficiency particulate absorber, but the ‘absorber’ has come to be replaced by ‘air’. Virtually all air purifiers and systems use HEPAs: they are made from extremely fine plastic or glass fibre threads, layered to trap particles such as pollen, mold, dust and pet dander. 

These can all be potent allergens, and if you suffer from hay fever, spore allergy or an animal allergy, for example, a HEPA-enabled purifier should help you. 

There have been reports from those with allergies to VOCs that HEPA-only purifiers help, but pure HEPAs cannot filter small chemical molecules to any meaningful degree. The benefits experienced in these cases could theoretically be placebo effects, but are more likely to be due to the reduction in allergenic material in the environment. Filtering pollens and dusts, for example, may ‘ease’ the pressure on your immune system, meaning reactions are generally less severe and some relief on usual symptoms is experienced.

There are also filters described as HEPA-type filters, which generally aren’t quite as powerful as ‘true’ HEPAs. 

There are few HEPA-only products now available. For example, in the UK, Homedics products are popular and affordable — both the AR-10 model and the AR-20 model are HEPA-only. The Vax Pure Air 300 Air Purifier has an accreditation from Asthma UK and approval from the British Allergy Foundation. 

 

2/ Carbon Air Filters

AustinAir Healthmate Plus

In order to trap gases, fragrances and chemicals, however, an activated carbon filter is required. Made from treating carbon with oxygen, which helps boost its surface area, activated carbon is superb at adsorbing chemicals on its huge surface. 

The activated carbon filters on the market are generally equipped with HEPA technology too — these might be described as a combination filter. HEPA filtering is usually performed first, and then the resulting particulate-free air is then filtered through the carbon.

This option is best for those with allergies to multiple materials — both organic matter and chemical compounds. 

That said, if of the ‘chemical’ allergies you know for certain that you are only sensitive to fragrances, you may not need a carbon filter if you apply other precautions. For instance, if you have a ‘no fragrance’ house rule, stick only to fragrance free household detergents and cosmetics, do not use air fresheners or perfumes, there may not be a need to get a carbon filter. 

However, they could come in handy, for instance when decorating, when it is extremely difficult to fully avoid VOCs. Perhaps chief among them are the isothiazolinone preservatives in paints, a huge problem for those allergic to them. Although there are some isothiazolinone-free paints available, they can be expensive and difficult to obtain. Activated carbon filters may reduce reactions to the ‘off-gasing’ which can persist from painted walls for many weeks, and therefore may be worth an extra investment for such periodic exposure.

It’s important to look for activated carbon (or activated charcoal — the same thing), as these are more effective, and for purifiers with much more than a few granules or a thin layer of it. Ordinary carbon or charcoal filters may be enough to help with odours, but aren’t going to be as good at removing chemicals to which you may be sensitive.

Among those considered the best for allergy, often popping up as a recommendation on allergy social media groups, are the IQAir HealthPro (US) or IQAir HealthPro Plus (UK / Can) models. They use a triple filtering system — a ‘pre’ filtering layer to tackle larger particles, a ‘gas and odour’ filter of activated carbon and impregnated activated alumina, and finally a ‘hyper-HEPA’ filter, which is more powerful than the minimum HEPA standard, and can can also filter out any carbon which loosens from the carbon layer. There is also the double-filter IQAir HealthPro Compact, which is smaller, more affordable, and incorporates its activated carbon filtering into the ‘pre’ layer. 

In the UK, their equivalents respectively appear to be the IQAir HealthPro 250 and the IQAir HealthPro 150

These may be out of the price range of some, and there is a range of lower (and indeed higher) price points. At the lower end of the scale, you may like to look at the Levoit LV-132 Model, for example, but which only has several ounces of activated carbon (as opposed to the several pounds in the IQAir models). Activated carbon — necessary for filtering VOCs — and the models which can incorporate substantial quantities of it, do not come cheap … 

 

2b/ ‘Carbon Plus’ Air Filters 

Dyson Pure Hot & Cool Link

Supplementary to activated carbon, you may come across some filters which further boost filtration capabilities with add-on technologies.

One is zeolite. This is a porous mineral made up of silicon compounds, aluminium and oxygen, and it is said to be better able to trap gases and pollutants consisting of very small molecules, such as carbon monoxide (which activated carbon isn’t very effective against), as well as ammonia and formaldehyde, which some may be sensitive to or wish to take steps to avoid for health reasons. One such purifier is the Austin Air HealthMate Plus (US) / Austin Air HealthMate Plus (Can / UK).

Another is tris, used by the very highly regarded Dyson Pure models — Cool Desk, Cool Tower and Hot & Cool Link. Tris is a chemical which can boost the adsorption of certain gases such as formaldehyde and nitrogen dioxide, and the Dyson charcoal in the filter is treated with it to further boost already excellent performance. This could be a better option if you are sensitive to formaldehyde-releasers or formaldehyde-releasing agents in the home. Formaldehyde can come from many sources — burning wood, tobacco, treated fabrics (which can release gases during ironing), building materials, paints, printers and many, many more, that it is extremely difficult to fully avoid in the home.

There’s another ‘boosted’ option from IQAir — the IQAir Multigas GC (US) / IQAir MultiGas GC (Can / UK), which comes with a ‘chemibsorber’ of aluminoxyde and potassium permanganate, which helps break down the likes of hydrogen sulphide and formaldehyde into carbon dioxide, and may be the best choice for those suffering from multiple chemical sensitivity (MCS). 

 

Other options

Many purifiers come with additional features, some of which are optional-use.

For instance, there are plasma / ioniser technologies in some air purifiers, which essentially ‘charge’ up atmospheric pollutants and chemicals so that they adhere to walls or can be more more easily filtered – either way, removing them from the air. There is some scepticism about this, however, as the process can produce ozone, which can worsen asthma, and there is not a lot of research on effectiveness for those with environmental allergies. On balance, it would seem wise to avoid if you do. 

Others use UV light technology, to help kill bacteria and viruses in the atmosphere. Again, some seem to produce ozone, however. 

 

Wearable air purifiers and filters …

By which I mean personal masks, of course! You may find this article — Allergy Face Masks — of interest for recommendations. 

2 Comments

  1. Sarah J

    I have lots of the allergies you mention so a few of the models would be good for me but I’m worried more about noise as the whirring / buzzing can annoy me on many purifiers or filters that i’ve tried or loaned before. Do you know which are best?

    Reply
    1. Alex G (Post author)

      I didn’t try any, sorry Sarah – I just compiled the article from an allergy perspective – who I thought particular models might be suited to depending on what manufacturers provided in terms of information. I think your best bet is to look at review sites if you’re concerned about noise issues. Remember some brands offer trial periods / money back guarantees etc. Look for ‘quite mode’ and other such claims.

      Reply

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