Pollen allergy, commonly called hay fever, is one of the most common chronic diseases. Worldwide, airborne allergens cause the most problems for people with allergies. The respiratory symptoms of asthma, which affect approximately one in twelve people, are often provoked by airborne allergens.
Although the number of people suffering with an allergy has increased in the last few decades, there is more education and a greater understanding of the immense impact that allergies have on our lives, from allergy symptoms to causes to treatments.
There is no clear explanation for the increase in allergies; however there are two main theories. The first theory is that awareness and diagnosis have improved in recent years and the second is that the increase in general air pollution and indoor air pollution have made allergens more common.
An allergy is characterised by an overreaction of the human immune system to a foreign protein substance (“allergen”) that is eaten, breathed into the lungs, injected or touched and which otherwise does not bother most people.
This immune overreaction can results in symptoms such as coughing, sneezing, itchy eyes, runny nose and scratchy throat. In severe cases it can also result in rashes, hives, lower blood pressure, difficulty breathing, asthma attacks, and even death.
People who have allergies often are sensitive to more than one substance. Types of natural allergens that cause allergic reactions include:
Allergy is not necessarily the same as sensitivity or intolerance to a substance. This is particularly so in the area of food where, for example, lactose intolerance is not classed as a food allergy because the symptoms do not arise from the immune system.
Scientists think that some people inherit a tendency to be allergic from one or both parents. This means they are more likely to have allergies. They probably, however, do not inherit a tendency to be allergic to any specific allergen. Children are more likely to develop allergies if one or both parents have allergies. In addition, exposure to allergens at times when the body’s defences are lowered or weakened, such as after a viral infection or during pregnancy, seems to contribute to developing allergies.
Each IgE antibody is specific to one particular substance. In the case of pollen allergy, each antibody is specific for one type of pollen.
IgE is special because it is the only type of antibody that attaches tightly to the body’s mast cells, which are tissue cells, and to basophils, which are blood cells. When the allergen next encounters its specific IgE, it attaches to the antibody like a key fitting into a lock. This action signals the cell to which the IgE is attached to release powerful chemicals, including histamine, which cause the symptoms of allergy.
The symptoms of airborne allergies are familiar to most people:
In people who are not allergic, the mucus in the nasal passages simply moves foreign particles to the throat, where they are swallowed or coughed out. But something different happens in a person who is sensitive to an airborne allergen.
In sensitive people, as soon as the allergen lands on the lining inside the nose, a chain reaction occurs that leads the mast cells in these tissues to release powerful chemicals, including histamine. These powerful chemicals contract certain cells that line some small blood vessels in the nose, causing fluids to escape and the nasal passages to swell—resulting in nasal congestion. Histamine can also cause sneezing, itching, irritation, and excess mucus production, which can result in allergic rhinitis.
The shortness of breath is due to a narrowing of the airways in the lungs and to excess mucus production and inflammation. Asthma can be disabling and potentially fatal.
Genetics: The risk of having an allergy amongst the general population is around 10-20%. However, If one parent is allergic, a child’s risk rises to 50% and if both parents are allergic, to 75%.
Age, sex, and siblings: On average, children are more likely to suffer from allergy than adults (children can sometimes ‘grow out of’ allergic disease) and the onset can occur at any age. More boys than girls have atopic asthma and hay fever, although this difference reduces in adult life. Children from large families and those with older siblings are less likely to develop allergies, probably because they are more exposed to childhood infection, which makes the developing immune system less likely to over-react to an allergen.
Early-life, or extreme/sudden, allergen exposure: It has been suggested that exposure to allergens like cigarette smoke, traffic pollution, dust, pollen, mould and pet dander in early life may increase a child's risk of developing an allergy. For example breast feeding for six months or more has been shown to decrease the risk of asthma and other allergies in babies. Premature babies are also more at risk of developing allergies than full-term babies.
The most common allergic diseases
Asthma is a disease of the lungs that causes airways to become blocked or narrowed making it difficult for you to breathe. It harder to breathe in than breathe out. Asthma attacks are caused by triggers which are either allergens (like house dust mite, mould, pet dander) or irritants like cigarette smoke, traffic pollution or cold air.
Asthma attacks are usually temporary, but if an asthma episode is severe, a person may need emergency treatment to restore normal breathing. Despite the far reaching effects of asthma, much remains to be understood as to what causes it and how to prevent it.
Asthma is potentially the most serious of the allergic diseases. In the UK, for example, during 2008-9, there were nearly 80,000 hospital admissions for asthma of which nearly half were of children aged 14 and under.
Although asthma can cause severe health problems, in most cases prevention and treatment can control it and allow a person to live a normal and active life.
Hay fever (seasonal rhinitis) is characterised by itchy nose and eyes, sneezing and runny nose. In the UK it is mainly caused by exposure to grass pollen (perennial rye and timothy grass).
Perennial rhinitis persists all year round. Sometimes people with perennial rhinitis do experience worse symptoms in the pollen season. Around 50% of those with perennial rhinitis have an allergy while the rest have some other problem with their nose or sinuses.
The most common airborne allergens
The ‘Allergy Season’
If you are allergic to pollen, you will need to be aware of seasonal variations. Other allergens like house dust mite, traffic and other indoor pollution, tend to be present year-round.
The pollen season varies for different plants and, in the UK, it lasts from early Spring to late Autumn.
Then along came Airora 4-in-1 ...
The levels of allergens and lung irritants are much higher in your home than outside. Traditional air purifiers can do little to help because of their limited ability to clear the air, and keep the air clear, of all of the types of allergen and pollution which might cause you problems. Only Airora 4-in-1 treats ALL types of pollution, in a WHOLE ROOM, in seconds (no filter required!).
In the open air, 'Hydroxyl Radical Cascades' are continuously created by the complex chemical interactions that occur naturally in the atmosphere. Hydroxyls are the powerful but entirely safe and natural air cleaning agent, often referred to by scientists as 'Natures Detergent', which continuously decontaminate the air and gives 'fresh air' that clean and refreshing feel that we all love.
Indoors, the natural atmospheric ingredients that continuously create hydroxyl radicals don't exist and allergens remaining active, smells remain smelly and bacteria and viruses constantly build up in the air and on surfaces. Consequently, indoor air is generally much more polluted than outdoor air, yet until recently it has received far less public attention.
We often spend up to 90% of our time indoors (at home, work or at school), so exposure to indoor air pollution is potentially much more damaging to our health. That is why the World Health Organisation considers indoor air pollution as one of the main health threats today, and states that around 3% of the global burden of disease is directly attributable to it.
Indoor air pollution
Indoor air pollution is a complex mixture of microbes and substances in the air that are potentially harmful to health. The composition of this indoor air pollution can vary greatly depending, for example, where you live and on the contents of your home.
In a home in a non-urban setting for example, house dust mite, pollen and mould spores can be a major cause of indoor air pollution and related health problems. In a new-build home or office, fumes from paints and insulation, new carpet and furniture can significantly contribute to the pollution. Especially in industrial or built up areas, traffic and industry pollution also play an increasing part in indoor air pollution.
In our homes the build up of both bacteria and viruses in the air is much greater than outside.
Sources of pollution
Damp dusting, not just dry dusting, is needed to reliably remove dust rather than just spreading it around. Most carpets are a major reservoir for dust and for every six rooms in a house around 40 pounds of dust is generated in a single year, much of which is human skin as we regularly shed our outer layer of skin as part of a continuous renewal process.
The main components of dust which can affect your health indoors are:
Prevention of indoor air pollution
It is always better to try to prevent indoor air pollution occurring before attempting to reduce or remove it:
Where the main source of pollution is internal rather than external, it is helpful to open windows after bathing, showering or cooking so that damp and mould don't build up.
An effective air purifier can play an essential part in reducing indoor air pollution in your home or place of work. But the key word here is ‘effective’ and the unfortunate truth is that most traditional air purifiers are not very effective!
Various types of traditional air purifier focus on different pollutants, typically pollens, spores and other particles or on gaseous pollutants. Some combine technologies to address more than one type of pollutant.
But all have the same drawback, they only clean the air passing through the device and rely, to only limited effect, on a high throughput of air to draw in pollution from the ever changing air in the room. However good the filter mechanism, they will only ever clean a modest proportion of pollutants from the air in a room because constant air changes, re-contamination, re-circulation and eddy formation means that there are always significant airborne pollutants in a room which have not been drawn into the device.
Then along came Airora ...
There is now however a new generation of air purifiers of which the Airora 4-in-1 is the first (and currently only) one. These air purifiers use the naturally occurring ‘hydroxyl radical cascade’ process found in the outside atmosphere to clean internal air (and exposed surfaces) of the full range of pollutants; allergens and irritants, pollutant gasses, bacteria and viruses and smells.
House dust mites are one of the most potent and common domestic and workplace triggers of allergic reactions.
Dust mites are microscopic eight-legged creatures called arachnids and they are closely related to the spider and the tick. They are found in every home and their presence is not an indication of poor cleaning!
It is not the dust mite itself which is the allergen but enzymes (proteins) found in its droppings and decaying body. The whole droppings themselves are particles between 4 and 20 microns in size but may crumble into particles as small as 0.5 microns across.
House dust mites feed upon the skin scales naturally shed by humans and other animals which are found in house dust. Although their presence is harmful to people who become allergic to them, dust mites do not bite or spread diseases.
While usual household insecticides have no effect on dust mites, fortunately there are multiple ways to reduce exposure to dust mite allergens in your home.
Dust mite allergy
As with other allergens, dust mite allergens cause an ‘over-reaction’ of the immune system in an allergic person. In allergy sufferers Immunoglobulin E (IgE) antibodies present on the surface of mast cells trigger the release of histamine when allergens stick to these IgE antibodies. It is histamine that produces the characteristic symptoms of an allergic reaction.
Dust mites love homes
Dust mites love humidity
To survive, house dust mites absorb water from the air. When humidity is less than 50% they tend to dry out and die. They also prefer temperatures around 21°C (70°F).
It is thus crucial to get rid of damp in your home. Ventilate by opening windows, and check for condensation in the kitchen and bathrooms. If you live in a humid area, consider buying a dehumidifier but remember that very dry air can be uncomfortable especially if you suffer with sinus or respiratory conditions.
Getting rid of dust mites in your home
The fight is never ending - dust mites are everywhere and even if you can get rid of all of them in your home, new ones would still appear (they are carried into your home on people’s clothing, for instance). So, look for long-term solutions which will reduce your house dust mite burden.
These measures will create an environment that could seriously reduce the house dust mite burden in your home.
Anti-mite spray and powder
Regular use of an anti-mite dust spray or powder can be of help. An anti-mite spray can penetrate mite reservoirs in carpets, soft furnishings and mattresses and anti-mite dry powder carpet cleaner can help get rid of mites where they nest.
When choosing allergy cleaning products, be careful to use cleaning products with natural ingredients. Spraying a chemical, especially on a regular basis, can be a severe trigger for people suffering with allergies.
Dust mites are not the only allergen in house dust
Cockroaches are commonly found in crowded cities and in, for example, the southern United States. Certain proteins in cockroach feces and saliva also can be found in house dust. These proteins can cause allergic reactions or trigger asthma symptoms in some people, especially children. Cockroach allergens likely play a significant role in causing asthma in many inner-city populations.
Can an air cleaner help?
While numerous manufacturers of ‘air cleaners’ / ‘air filters’ claim to be able to clear dust mite allergens from the air, they can only reduce, not eliminate, the problem, because:
You can learn more about why traditional air cleaners don’t work well here and why Airora’s unique technology does work here.
Rhinitis, including hay fever, is the most common of all the allergic diseases. The typical symptoms such as blocked nose, watery eyes, & running nose may persist all year round (perennial rhinitis) or may be seasonal. Even though it’s often undiagnosed and its symptoms often thought of as harmless, the impact perennial rhinitis can have on a person’s overall quality of life can be significant.
What is rhinitis?
Rhinitis is inflammation of the nose. It may, or may not, be caused by an allergy.
Another symptom of perennial allergic rhinitis is post-nasal drip, where mucous runs down the back of the nose and then into the throat and the airways, producing a persistent phlegm cough.
Causes of allergic rhinitis
Allergic rhinitis is caused by exposure to an airborne allergen. Common allergens include:
What happens when the allergen is breathed in
In allergic rhinitis, blood flow is increased, the mucous membranes swell and there is increased mucous production, all occurring in response to histamine production on exposure to the allergen. The result is nasal congestion, nasal blockage, and/or a runny nose.
Allergic rhinitis diagnosis
A simple description of your symptoms and their seasonality may be all that is required to diagnose rhinitis.
If confirmation and/or identification of an allergic cause is needed, then a skin prick test can be used. A tiny drop of allergen extract is placed on the skin at either the arm or the back. If you are allergic to the substance, a small red weal will appear within a short period.
Allergic rhinitis can be reduced by avoiding exposure to allergic triggers, for example:
House dust mite
Medical treatments for allergic rhinitis
If your symptoms are mild, you can use a long-acting non-sedating antihistamine such as Claritin (loratadine), NeoClaritin (desloratadine), Zyrtec (cetirizine), Xyzal (levocetirizine) or Allegra (fexofenadine). These are available without a prescription, but you should always consult your pharmacist before use.
The older antihistamines like chlorpheniramine (Piriton) and hydroxyzine (Atarax) have a significant sedating effect and should not be used if you are driving, operating machinery, or studying. These older drugs also interact with alcohol so having even a small amount to drink may significantly affect performance.
If rhinitis mainly affects your eyes, antihistamine eye drops, such as Otrivine (antazoline) may help.
In addition to an antihistamine, a nasal decongestant (drops or a spray) may also be helpful in clearing a blocked nose. Some of these decongestants are corticosteroids, which act by reducing inflammation including Beconase (beclomethasone) and Flixonase (fluticasone). Non-corticosteroid nasal decongestants include Otrivine/Sudafed (xylometazoline). All of these can be bought without a prescription. However, only use a decongestant for as short a time as possible, as the nose tends to stop responding to these medications over time.
In general, antihistamines and topical nasal steroids are most effective against seasonal allergic rhinitis/hay fever but may still help with perennial allergic rhinitis.
Can an air cleaner help?
While numerous manufacturers of ‘air cleaners’ / ‘air filters’ claim to be able to clear those allergens leading to rhinitis from the air, they can only reduce, not eliminate, the problem, because:
However, evidence has been increasing for some time that all of these products contain industrial chemicals which can, among other things, damage lungs, aggravate asthma and cause tumours.
Sprays, plug-ins and gels
Chemical sprays, plug-ins and gels for home perfuming are hugely popular but they can include an array of hazardous substances which may cause lung damage and tumours, interfere with our hormones and aggravate conditions such as asthma.
Many air fresheners employ carcinogens, volatile organic compounds (which are characterised by their low boiling point which mean they form a gas at room temperature) which are known to increase the risk of asthma in children and known toxins such as phthalate esters in their formulas.
The evidence of harm is mounting:
But manufacturers refute such concerns
Manufacturers of air fresheners, however, maintain that their products are safe. In June 2015, SC Johnson, which makes Glade air fresheners, published specific information on most of the ingredients in its products for the first time.
Company chairman Fisk Johnson says: 'We take great care in making ingredient choices to offer products that are both safe and effective.'
However, not all of the ingredients used in the actual perfumes are fully listed and could well be made up of many different chemicals.
However, SC Johnson maintains that all its fragrance ingredients, even those not listed, are safe: 'While they are not disclosed, the remaining ingredients also must meet our strict standards.'
Incense are no better
Millions of us burn them every day to send spiritually inspiring wafts of spiciness around our homes. Research shows that ingredients such as frankincense can cause chemical changes in our brains, lifting our moods.
However, incense's mystic allure has been clouded by new findings warning that its fumes may be more dangerous than cigarette smoke, causing cancerous mutations in our DNA.
Burning incense releases tiny chemical particles which can become trapped in our lungs, causing potentially dangerous inflammatory reactions.
The research also found that incense particles from commonly used ingredients agarwood and sandalwood are more toxic to our cells' DNA than tobacco smoke.
Nor are scented candles
Scented candles bring another dimension, adding that subtle hint of aromatic bliss. Scientists remain unmoved however, voicing extreme concerns about the pollution that they are bringing to our lives.
In March 2015, a team of experts tested six scented candles, with such aromas as clean cotton, strawberry and kiwi fruit.
Behind their labels, however, lay a host of potentially dangerous industrial chemicals, including formaldehyde at levels which, with long-term exposure, are known to raise the risk of respiratory problems and cancer.
The candles also gave off significant levels of VOCs. Furthermore, the study warned that you don't even need to light such candles because simple evaporation will enable them to pollute your home.
Most scented candles are made with paraffin, which brings other problems. The oil by-product gives off ultra-fine soot particles containing acetone, benzene and toluene, usually seen in diesel emissions, and known carcinogens.
Then along came Airora 4-in-1 ...
Why try to 'cover up' smells such as wet dog, cigarette smoke, damp, toilets and cooking? Airora 4-in-1 simply removes such smells and creates a wonderfully fresh, clear and clean atmosphere. Don't just take our word for it, our independent test panel says Airora makes them feel:
Noise pollution adversely affects the lives of millions of people. Multiple studies have shown the direct links between noise and health.
According to one study, around 50,000 people in just the European Union die prematurely each year from heart attacks caused by traffic noise. Another study showed that people living in streets with average noise levels above 65-70dB, the average risk of heart disease is 20% higher than for people living in quieter streets.
Other problems that have been proven to be related to noise include stress related illnesses, high blood pressure, speech interference, hearing loss, sleep disruption, and lost productivity.
Traditional filter-based air purifiers
Most air purifiers on the market use HEPA or Electrostatic filters, and these air purifiers typically create a noise of over 70dB at their most effective (highest) fan speed. Indeed, manufacturers tacitly recognise that this noise level is unbearably high in the home, so most have a ‘sleep’ / ‘quiet’ mode which makes them a little quieter but effectively cripples their effectiveness!
In other words, to use a traditional air purifier at its most effective fan speed, exposes people to a noise level similar to street traffic inside their home.
In fact, according to the World Health Organisation’s Night Noise Guidelines, above 40db (rainfall, a refrigerator or an air conditioner at 100 feet, a quiet suburb) of noise can have adverse health effects and noise at this level may well affect most people’s sleep.
So-called ‘silent’ air purifiers
You may have come across ‘silent’ air purifiers, these are air purifiers without a fan.
There are basically two types of ‘silent’ air purifier:
And then there is Airora …
This means that hydroxyls can reach every nook and cranny of a room within seconds, acting on all of the air and all exposed surfaces.
Mould spores are a potent allergen that can trigger severe asthma and rhinitis symptoms and cause a broad range of respiratory conditions. It occurs both indoors and outdoors and the density of mould spores is normally much higher than that of Pollen.
Mould spores, sometimes also called fungal spores, are light and are therefore readily carried through the air of your home or office. This is because their diameter is between one and 100 microns, depending on species, with most being between 2 and 10 microns. Moulds come in a variety of colours: white, grey, orange, green, pink and black.
Your first step in keeping the mould count under control is to ensure that you tackle any damp areas. Another important step is to neutralise mould spores in the air and on surfaces, to prevent the mould from spreading.
Types of mould
When inhaled, tiny fungal spores, or sometimes pieces of fungi, may cause allergic rhinitis or trigger an asthma attack. Because they are so small, mould spores also can reach the lungs.
In a small number of people, symptoms of mould allergy may be brought on or worsened by eating certain foods such as cheeses processed with fungi. Occasionally, mushrooms, dried fruits, and foods containing yeast, soy sauce, or vinegar will produce allergy symptoms.
Mould spores can also cause Allergic Bronchopulmonary Aspergillosis (ABPA) which is an allergy to the spores of Aspergillus fumigatus. Around 5% of adults with asthma develop ABPA at some time during their lives.
Where do moulds grow?
Mould loves damp conditions, so you will tend to find it in places such as:
What is the best way of preventing indoor mould?
Keep your home or office well-ventilated and dry, and discourage the dispersal of mould spores:
A mixture of bleach and water, a mixture of white spirit and surgical spirit, or a specialised anti-fungal spray can be used to get rid of mould patches. Mould tends to reoccur, so you may well have to repeat your cleaning operations.
Can an air purifier help?
While numerous manufacturers of ‘air cleaners’ / ‘air filters’ claim to be able to clear mould spores from the air, they can only reduce, not eliminate, the problem, because:
A study on Household Cleaning Sprays and Asthma by Professor Zock of the Municipal Institute of Medical Research in Spain, was published in the American Journal of Respiratory and Critical Care Medicine in 2007.
Professor Zock undertook the research as ‘Cleaning work and professional use of certain cleaning products have been associated with asthma, but respiratory effects of nonprofessional home cleaning have rarely been studied’.
According to the study, the exposure to certain cleaning products during professional cleaning work has been associated with MCS and other asthma symptoms for some time. This study, however, focused on the respiratory effects of non-professional home cleaning.
The study identified 3,503 persons, in 10 countries, doing the cleaning in their homes and who were free of asthma at baseline. Frequency of use of 15 types of cleaning products was obtained in a face-to-face interview. The researchers studied the incidence of asthma defined as physician diagnosis and as symptoms or medication usage at follow-up. Associations between asthma and the use of cleaning products were statistically analysed.
Participants were assessed for asthma, wheeze, physician diagnosed asthma and allergies during follow-up. They were also asked to report the number of times per week they used cleaning products.
Two thirds of the study population who reported doing most of the cleaning were women. 6% of them had asthma at the time of follow-up. Fewer than 10% of them were full-time homemakers.
Risks were predominantly found for the commonly used glass-cleaning, furniture, and air-refreshing sprays. Cleaning products not applied in spray form were not associated with asthma.
The report's conclusions
American Journal of Respiratory and Critical Care Medicine Vol. 176. pp. 735-741, (2007); The Use of Household Cleaning Sprays and Adult Asthma, An International Longitudinal Study.
Asthma has become one of the most common chronic disorders in the developed world. Asthma is difficult to describe, but the International Consensus Report on the Diagnosis and Management of Asthma defines it the following way: “Asthma is a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role".
Throughout the developed world, typically 5% of adults and 10% of children have clinically significant asthma. Its prevalence has increased significantly over the last 25 years and is now thought to affect around 300 million people worldwide.
Asthma can be a serious condition, which occasionally proves fatal, accounting for 1,131 deaths in the UK in 2009. However, most deaths and hospital admissions for asthma are preventable. Asthma is a condition that can be managed successfully and part of that management should include a strategy for allergen avoidance.
For example, in the UK, around 5.4 million people suffer from asthma, which includes 1.1 million children. The condition costs health services around £1 billion a year and accounts for an annual 1.1 million lost working days and around 80,000 hospital admissions.
Asthma comes in several forms
There are two primary types of asthma – childhood onset and adult onset. Most asthma does begin in childhood and is often associated with other related conditions like eczema and rhinitis.
Childhood onset asthma often has clearly identifiable triggers which will bring on an attack.
Adult onset asthma may be a continuation of childhood onset asthma, or it may be a new onset of the condition. Asthma can occur at any age, and should be considered in anyone who has a chronic cough. In adult onset asthma, there is often no obvious trigger, except for a chest infection.
There are also several sub-categories of asthma, including:
It can run in families
Asthma tends to run in families. However, asthma is not a single-gene disorder, with a clear line of inheritance. There are several ‘susceptibility’ genes involved in asthma, each contributing to the risk of developing the disease.
Diagnosis depends upon the doctor taking a careful medical history from the patient and noting whether the hallmark symptoms of wheeze, chest tightness, breathlessness, and cough are present. There are no laboratory or other tests which can definitely diagnose asthma and distinguish it from other lung conditions. However, if your doctor suspects asthma you may be subject to breathing tests to help confirm the diagnosis. Such tests include:
Spirometry: Spirometry is breathing into a machine which measures how much air you can exhale, which shows whether the airways are obstructed or not.
Peak expiratory flow rate test: A small hand-held device, called a peak flow meter, is used to measure how fast you can blow air out of your lungs in one breath. The peak flow meter can be a useful tool to use yourself at home to monitor your asthma.
Skin prick, or blood tests, are often carried out to find out which allergens might be triggering your asthma.
Thorough diagnosis by a doctor is a must, as asthma can easily be mistaken for other conditions, including:
Asthma tends to be a chronic disease (that is once you have asthma it will remain with you for the rest of your life). However, around a half of children do ‘grow out of’ asthma by the time they become teenagers, sometimes to re-emerge in adulthood. Like other chronic diseases, such as diabetes, asthma is not curable in the same way that, say, an infection can be cured. However, asthma can be controlled successfully so you can still live a full life.
Why all the focus on air filter efficiency?
Designers of traditional air purifiers have a tough job. There are lots of different air purifiers, so how to stand out from the crowd? Well, a little like high end music systems, ‘measures of performance’ are created which appear important to potential buyers but which are pretty meaningless in practice, and then competing products can be compared, and superiority claimed, based on that same measure.
One such misleading measure is ‘filter efficiency’ where you often see a focus on the percentage of particulates (pollens, mould spores, pet dander and house dust mite excretions) captured by the filter in the air purifier. For example “my filter captures 99.7% of all particles and yours only captures 99.2%”, or “my filter captures smaller particles than yours does” and so on.
And it isn't just the %, some manufacturers stoop to terms such as 'True HEPA' to muddy the waters, when in fact there is no such thing, a filter either meets the standard for HEPA filters or it doesn't!
Sadly, the fact is that such measures are pretty much meaningless in the real world. But, you say, surely it matters how much of the particulates in the air, which may well be allergens, irritants and other pollution, the device filters out?
My reply is that there are at least two major problems with using this measure of air purifier effectiveness, both of which make the number, be it 90%, 95% or 99.97% ( or even in fact 100%! ), pretty much meaningless!
The filter % measures the wrong thing
Measuring the percentage of particulates that are captured from the air passing through the filter measures only that, the percentage of particulates captured from the air passing through the filter. It doesn’t measure the percentage reduction of particulates in the air in the room, and the relationship between the two is tenuous at best!
The unfortunate truth is that the air in the room is constantly changing (typically it is replaced hourly with contaminated air from outside and elsewhere in the home), the air passing through the device is immediately remixed with unclean air in the room and some of the air in the room never goes through the device at all. Some air never goes through the device because of insufficient air flow, temperature stratification and the formation of eddies (where the air in parts of the room rotates in a circular motion without ever moving through the air purifier).
Furthermore, as pointed out by the US Environmental Protection Agency;
"for typical room sizes, most portable air cleaners currently on the market do not have high enough air flows to effectively remove large particles such as pollen, dust mite and cockroach allergens"
The reason being that the larger (and heavier) particles, such as pollen, simply sink to the floor or onto other surfaces, ready to be re-distributed into the air when they are next disturbed!
If you model how air cleaners work and include the constant infiltration of polluted air from elsewhere, they can take hours to reach a stable minimum of pollution and that minimum is related to many factors, but only marginally to the efficiency of the filter itself.
Think of it this way, imagine that an air filter, which captures 99.7% of particulates, effectively reduces the amount of particulates in the air of a room, after several hours, by say 50%. Changing the filter to one which captures only 90% will only have a marginal effect, perhaps limiting the reduction to, say, only 46%.
Be it either 50% or 46%, it doesn’t matter – neither are nearly enough!
What about gasses?
Well, a HEPA filter only ‘traps’ particles down to a particular size, below that size they are not captured at all. And all of the basic technologies, HEPA, electrostatic and ionic completely fail to capture or neutralise polluting gasses which can themselves be breathing irritants and cause asthma attacks.
Then along came Airora ...
The problems outlined above have earned traditional air purifiers a poor reputation, to the point where physicians will generally only say “well try one, it might help”.
Dr Wyatt blogs on his lifetime's experience of Indoor Air Quality Issues.