Air Cleaners

Air Cleaners2024-02-13T13:13:03+00:00

Air Cleaners

On average, people spend up to 90% of their time indoors, and indoor air can be two and a half times as polluted as outdoor air.

Indoor Air Quality is of particular concern for those affected by asthma and allergies, but a healthier home is of broader benefit to all.

The asthma & allergy friendly® Certification Program seeks to assist people to identify products which will make a genuine difference to their indoor environment. It develops certification standards for relevant categories of products, and all certified products undergo testing to those standards. In this way, the consumer can then make an informed choice about materials like insulation, flooring products, etc. that they bring into their home.

In the case of air cleaners, we test the product in an environmentally-controlled chamber, using test dust that contains allergens. It is important that the air cleaner can remove allergens from the air, and that these are captured in the filter of the air cleaner. Different allergens act differently in the air, because they have different sizes and features. Our standard addresses these issues.

Our air cleaner standard is one of over 50 standards in the asthma & allergy friendly® Certification Program, covering appliances, bedding products, air filters, building products, and services that can have an impact on the indoor air environment. You can explore the air cleaner standard in more detail using the menu on the left, or use the links above to explore other standards.

Brand Promises for Healthier Home: An Interview with Ingersoll Rand

It’s no secret that consumers are demanding products that are safer and healthier for themselves and their families. But many brands are capitalizing on this by making health claims that are scientifically unfounded. What separates the companies that are delivering on their brand promise from the ones that are not, and how can companies tighten their messaging to cut across the noise?

Here, Allergy Standards’ Digital Marketing Manager, Léa Daulan, interviews leaders, brand managers, and marketers who are part of a global movement towards healthier products that are rooted in rigorous science. In this interview, meet Jay Ayers, IAQ Product Manager, HVAC Residential HVAC & Supply at Ingersoll Rand

Ingersoll-Rand-Trane-Clean-Effects-Allergy-Standards-2019Léa Daulan: The CleanEffects™ is the very first whole home air cleaner to earn the asthma & allergy friendly® Certification Mark, making Trane an innovator in its field. Why was it important for Ingersoll Rand to fill in this gap and to become CERTIFIED?

Jay Ayers: We felt like we had the best premium whole home filter product on the market, so we wanted to partner with an advocate as dedicated to clean indoor air as we were and who was promoting its importance, especially to those with asthma and allergies. The Asthma and Allergy Foundation of America (AAFA) offered the very best program in collaboration with a third-party standards body, Allergy Standards, so the validation was totally independent, and the standards to meet the program requirements were very stringent. Getting CERTIFIED by this program validated our hypothesis that the Trane CleanEffects™ whole home air cleaner is a very good product.


Léa: What type of scientific testing did the CleanEffects™ undertake to become asthma & allergy friendly® CERTIFIED?

Jay: To be included in the program, our product was tested by Allergy Standards via one of its partner labs, Airmid Healthgroup. The tests are very specific and unique because they test in a simulated home environment, whereas most filters are tested in air duct chambers and rated for efficiency at a distance only 4 inches away from the filter. By using the certification methodology, we can see not only the measured efficiency of the filter but the filter’s effectiveness over time. We call that the Clean Air Delivery Rate, or CADR for short.  It is one thing to say that your filter is efficient, but it is another thing to say that your filter is efficient and effective at removing particulates and pollens from the indoor air.

In order to become CERTIFIED, the CleanEffects™ was required to pass a specific percentage of removal of dust mites, cat allergens and grass pollen from the test room within a 30-minute period. These are three of the most common indoor allergens that trigger respiratory distress in allergy / asthma sensitive people.

It also was important to verify that Trane’s reusable collector cells (filter) are long lasting and deliver a lower maintenance cost than the competition’s air cleaners that require filter replacements at least annually. The Certification Program tested the recovery rate of our air cleaner and reported a 98% recovery rate of the original efficiency level before cleaning. This test was repeated over 10 use and clean cycles, which means that consumers can expect 5 years of efficient performance before purchasing new replacement cells.

The main takeaway from these rigid tests is that our filter can take a lot of dust and still maintain effectiveness without costing consumers the monthly filter replacements.

Separately, Trane wanted to carry the testing even further by testing for removal of common influenza virus, which makes people sick, by filling a test room with 3 times the amount of influenza virus that could be expected in a normal home. The results proved a 99% reduction of the influenza virus in the room within 30 minutes of turning on the CleanEffects Air Cleaner.

Léa: Was the data you received from the testing report with the high performance of your product against our scientific standards helpful to enable you to differentiate your product; and how have you translated the leading technological features of the CleanEffects™ in your marketing messaging?


Yes, it helps us differentiate our product tremendously because we are the only whole home air cleaner product that has passed these rigorous standards.

So, we really emphasize the effectiveness of CleanEffects™ for taking things out of the air. Not only does our product remove pet dander and allergy pollen from of the air – which are in the 2- to 5-micron size particle category (and many of less efficient media type filters do a good job at that level), but but the CleanEffects™ also takes out the sub-micron (less than 1) particles that go into people’s lungs such as mold and influenza virus. Those particles are the ones that most affect people suffering from asthma and allergies, and that’s our differentiating message.


Léa: In what ways do you utilize third party Certification Marks and testing programs to validate claims?

Jay: We added the asthma & allergy friendly® trademark on all our marketing literature and we have added the label on the product door as well as the outer packaging. We also have shared our story with consumer and trade media through paid and earned opportunities. Plus, we have featured the Certification Mark at all our national trade shows.

The mark is a true differentiator for our product.


Léa: Do you feel that consumers are becoming more concerned about air quality in their home?

Jay: Absolutely.

We recently participated in a survey of American homeowners and found almost to 60% of those surveyed ranked indoor air quality concerns as 8 or higher on a 10-point scale, with 10 representing most important and 1 representing the least. So, yes, it is quite important to consumers.

The highest rated concerns were mold, carbon monoxide, bacteria, viruses and pollen. With the CleanEffects™ efficiency and high CADR (Clean Air Delivery Rate)  we are able to filter out four of the five leading concerns, with carbon monoxide being the only exception. Of course, there are specific monitors available on the market specifically to address carbon monoxide concerns. We also targeted people with pets and with children who suffer from asthma and allergies. With 60 million people in the U.S. suffering from asthma and allergies, our survey discovered that a significant percentage of productivity is lost from employees missing work due to allergy and asthma distress. Making sure that the home environment is healthier is not only beneficial to business but is a necessity for those who are severely impacted by these health issues.


Ingersoll-Rand-Trane-Clean-Effects-Allergy-Standards-Léa: How does the CleanEffects™ help consumers to create healthier environments in their homes?

Jay: Connected to the home’s HVAC system, CleanEffects™ filters the air continuously, running every time the heating and cooling system turns on. In a typical home, that means the air is filtered about 5 to 7 times in a 24 hours period, during which 100% of the home’s air passes through CleanEffects™. Each time the air passes through the patented IFD™ technology filter, the system takes out more indoor pollutants. As people come and go from their homes, they also bring in additional pollutants, so it’s important that our filter works continuously to keep our customers’ home clean and healthy. The CleanEffects™ filter may be cleaned with a vacuum or a blower, usually twice a year, to keep the filter in peak condition.


Léa: What are Trane’s objectives in 2019 to best meet rising consumer demand for healthier products?

Jay: We are constantly developing and bringing to market new and better products to improve the health, well-being and comfort of consumers. One of our newest product categories is ventilation. Trane not only wants to clean the air, but also ensure that fresh air is introduced into the home. According to the EPA. indoor air has been found to be as much as 5 times more contaminated than outdoor air. We are also doing work around the accuracy and consumer interest of indoor air sensors that could detect and inform consumers about changing indoor air quality and conditions inside their home. It is an exciting time to be focusing on Indoor Air Quality as consumer awareness has increased exponentially around the topic.


Léa: For people looking to purchase this product the CleanEffects™, where can they find it?

Jay: We sell though company owned and independent distributors who sell to installing trained dealers and contractors. For more information, go to


Léa: Thank you. 

Standard Abstract 08-01: Air Cleaners

Air Cleaners that are Certified asthma & allergy friendly® are tested to the ASP:08-01 Air Cleaner Certification Standard. The Certification Standard utilizes an algorithm of proprietary and recognized scientific techniques to assess Air Cleaners for their ability to reduce allergenic and irritant materials. Submitted Air Cleaner models that pass certification testing are granted a certificate stating that the particular Air Cleaner meets the requirements for the asthma & allergy friendly® ASP:08-01 Certification Standard.

Allergy Standards Ltd (ASL) subjects the Air Cleaner to allergen measure based performance testing to ensure that the Air Cleaner reduces total allergen burden that remains airborne. Assessment for certification requires that the Air Cleaner be evaluated in terms of indoor allergen levels that are representative of those found in both air and surface samples of typical homes. The asthma & allergy friendly® Certification mark is awarded to those air cleaning products that have been scientifically demonstrated to contribute to the goals of allergen reduction.

Part 1: Effective airborne allergen removal

For each of the allergen test conditions, the reduction of allergen must be at least 90% lower than the natural decay under that condition.




Pass/Fail Criteria



Removal of airborne allergen


Demonstrable for one or more of the allergens tested


Part 2: Effective retention of allergen




Pass/Fail Criteria

Retention of removed allergen within the air cleaner (recovered from filter media)



Part 3: Types of air cleaners assessed

Media based air cleaners alone are considered in this protocol number, while other technologies are not eligible for certification under this standard.

Part 4: Ozone 

The Code of Federal Regulations (CFR) section 21:801.415 requiring ozone exposure at less than 0.1 mg/m3must be achieved.

All CERTIFIED asthma & allergy friendly® paints are associated with a unique Certification code.

Why and how we certify air cleaners – a Q&A

There is ever-increasing awareness of the chemicals and allergens we come into contact with every day, particularly if you or a member of your family has asthma or allergies. We created the asthma & allergy friendly® Certification Program to help you improve your indoor environment by identifying products and services that can help to reduce allergens and create a healthier home environment.

But what is it that makes some air cleaners better for the indoor environment than others, and where do we draw the line to decide to certify an air cleaner as asthma & allergy friendly® ? We hope that the questions below will clarify this. Let us know if you have more questions!

Why do we certify air cleaners?

Our goal in the asthma & allergy friendly® Certification Program is to create a healthier indoor environment for you and your family, as well as to reduce allergens in the home. So we look at all elements of the indoor air environment.

Effective air cleaners can help to remove airborne allergen from a room. Different allergen particles have different sizes and they behave differently in the air. For example, while pollen particles can be relatively large (up to 100 micrometers), cat allergen particles can be as small as 1 micrometer wide. A micrometer is one thousandth of a millimetre. By comparison, the width of a human hair ranges from 20 micrometers to 180 micrometers.

Allergen particles in the air sometimes remain suspended in this zone where they can be breathed in, or they can settle on surfaces like chairs and the floor. If they have settled on a surface, activity or motion can move them back into the breathing zone.

When we test air cleaners, we look to recreate what happens in the home, so that we are testing the appliance in a way that is relevant to users. We make sure that the air cleaner is removing allergen from the air, but we also make sure that the allergen is being captured by the air cleaner, instead of just settling in surfaces in the room.

How do we test air cleaners?

  • We use a controlled environmental chamber to test air cleaners.
  • We set this up to mimic a room and use carpet as the flooring.
  • We add some items of furniture to the chamber, like a table and chair, so that there are surfaces where allergen can settle, like in household rooms.
  • We then introduce test dust that contains allergen into the room through a vent.
  • We run the air cleaner and monitor the particle level in the room.
  • We also do a test with no air cleaner so that we can compare the two scenarios.

1. Removal of Allergen

Once the test is finished, we suck all the air out of the room through a filter, so that any allergen that remains in the air is captured. We compare this to the amount of allergen in the air when there is no air cleaner in the room. Our requirement is that there must be at least 90% less allergen in the air when the air cleaner is operating.

2. Capture of Allergen

Just because there is less allergen in the air when the air cleaner is operating doesn’t mean that the air cleaner is capturing the allergen. It could be that the allergen is settling on the surfaces and the flooring, or even on the walls. This takes it out of the breathing zone, but it could be reintroduced to the breathing zone if somebody walks on the floor or rubs against the wall.

We test the filter of the air cleaner, to make sure that at least half of the allergen removed from the air is captured in the filter.

3. Ozone

Some appliances can produce ozone as a side-effect of their operation. We make sure that if certified air cleaners do produce ozone, that it is at an extremely low level so it is unlikely to have an impact on the indoor air environment. Our certification requires that certified air cleaners must achieve < 0.1 mg/m3 ozone exposure. We apply the same guidelines as the US Code of Federal Regulations.

What do we look for in electrostatic/ionizing air cleaners?

Ionizers release charged particles (ions) into the environment – these have either a positive or negative charge, and when they transfer this charge to an allergen particle it causes the allergen particle to stick to a surface, removing it from the breathing zone. Because there is some research that supports the safety of negative ions, we require that the majority of ions produced by this type of air cleaner are negatively charged. These air cleaners must still meet all of the criteria listed above, to make sure they remove allergen from the air, capture it in the appliance’s filter, and do not release ozone.

Do we certify in-duct air cleaners?

Yes, we have a certification standard for in-duct electrostatic air cleaners. To test this type of air cleaner, we install the air cleaner in a duct connected to an environmentally controlled chamber. We introduce allergen-containing test dust to the chamber, and monitor the allergen levels and the general particulate levels in the chamber over a 24-hour period. We require that the allergen levels are reduced by 70% at multiple times over the 24-hour period, and that general particulate levels are reduced by 75% multiple times over the 24-hour period. We require the same low ozone emission as we require for all air cleaners. Finally, we require that the performance of the in-duct cleaner after cleaning is within 2% of the initial performance, to make sure that its performance does not drop over time.

What else do we certify?

We have over 50 different asthma & allergy friendly® certification standards for products and services, addressing all areas of the indoor air environment. Some of these relate to products which remove allergens and dust from the indoor environment, like vacuum cleaners, air cleaners, dehumidifiers, and washing machines. Some of them relate to products where it is important not to provide an easy home for allergens and that it is possible to remove allergen from them – like bedding, toys, and flooring. And some of them relate to household products that should make as little an impact on the indoor environment as possible – like flooring and paint.

You can find out which products are certified asthma & allergy friendly® and read more here:

How To Take Care Of Our Indoor Air?

Maybe you live in the city, maybe you have a family member with asthma or other respiratory issue, maybe you have just realised how polluted our indoor air is and want to live in a healthier home. Whatever the reason, you have come to the conclusion that you need an air purifier. Or, wait, is it an air cleaner you need? What about an air filter?

It’s a minefield out there when it comes to the terminology, technology, effectiveness and variety of models that you can choose from. How do you know what’s right for you? Let me try to simplify a few things for you.

What’s in a Name?

Most manufacturers use the terms air cleaners and air purifiers interchangeably. Some refer to air cleaners as the products with a HEPA filter and purifiers as those that use Ultra Violet light, negative ions or ozone to clean the air. Often the devices use a combination of these with the ultimate goal of removing pollution- particles and gases – from the air.

So, the technologies available are:

1. HEPA Air Filter

Simply put, this is a fine mesh with flaps folded bit like an accordion, that traps particles as air is pushed through it by a fan. It can trap 99.97% of particles 0.03microns or larger. That includes pollen spores, pet dander, dust mites and some bacteria. This is a great option if you have an allergy sufferer in the house.

There is a bit of maintenance involved in that the filter has to be changed every two to three months or its effectiveness deteriorates. Some devices have a helpful indicator to remind you that the filter needs changing. Most HEPA filters also have a prefilter that removes larger particles and prolongs the life of the HEPA filter.

On the down side, a HEPA filter will not remove odours, chemicals or gases. For that you will need an activated carbon filter.

2. Activated Carbon filter

Interestingly, one of the first applications of activated carbon was to clean dirty water in the early 1900s. Subsequently it was used in gas masks to protect soldiers from poisonous gas in World War 1. 

When carbon is activated it becomes porous like a sponge, creating tiny holes within the carbon where pollutants get stuck, never to be released. All sorts of problematic pollutants can be trapped by carbon – bad odours, chemicals, smoke – so they are particularly useful for people sensitive to poor air quality. For instance, those nasty VOCs that are released by new furniture, cleaning products or paints are eliminated nicely by activated carbon.

Maintenance is necessary and depends on the thickness of the filter as well as the nature of the pollutants. If cigarette smoke is the main pollutant, for example, the filter gets saturated faster and will need more regular changing.

Because a carbon filter isn’t especially effective at trapping particulate matter, they are often combined with a HEPA filter.

3. Ultraviolet Sterilisation

A UV sterilizer uses the same UVA and UVB rays emitted by the sun to kill moulds, bacteria and even some viruses. A UV purifier can work well in the kitchen or bathroom, where the heaviest bacterial load is.

4. Ionic or Electrostatic

These technologies have become a bit controversial as some may generate ozone. Ozone is harmless in small amounts but it’s crucial that you check how much a device produces as, if inhaled in large amounts it can be damaging, especially to the very young, the very old or those with respiratory illness. Avoid anything that creates more than 50-60 parts per billion. Look for certification marks for reassurance that your device is safe. 

These purifiers work by producing negatively charged oxygen atoms which combine with dust, pollen or any positively charged ion and bonds with them. The resulting heavier particle then falls to the ground or, depending on the type of device, is trapped on a special collection plate. An ioniser therefore doesn’t eliminate or absorb the contaminants and so there is the potential problem of the particles becoming loose and re-entering the circulation.

An advantage of this type of purifier is that there is no filter and therefore no maintenance cost. If there is an ioniser plate, then this can simply be wiped clean and reused. This should generally done about once a week. These devices work against the smallest of particles including dust, pollen, bacteria and pet dander. They also tend to be low cost.


Size and Positioning Matters

Sick building syndrome Indoor Air Quality Allergy StandardsWhile it may be tempting to invest in the less expensive devices, think first of your problem and your goal. A single activated carbon purifier may be the best solution for a smelly utility room but if your aim is to reduce allergy triggers for your family, then you must factor in your whole house. My kids typically throw their worn clothes on their bed (bedrobe!) or the floor (floordrobe!) so any pollen tracked in from outside is disseminated throughout the house. When we walk around, we stir up dust which then travels just about anywhere.

A single purifier will only clean adjacent rooms not connected by a door or wall. We spend most of our time in the kitchen, living room, bedroom, office and basement, so consider each individual room’s problems and its occupants before choosing the right device. Positioning can improve the function too- if its cigarette smoke, position your purifier where the ashtrays are. A purifier by the door can help filter air as it comes into the room. In general, keep the device in a place with high air flow to maximise efficiency.

Finally, in a living area where people are continuously coming and going a purifier must be keptrunning 24/7. In a room like a bedroom or office where the door can be kept closed, then it’s only necessary to run the machine when the room is occupied.

Medical & Lifestyle Author Dr Anna O'Donovan

Medical & Lifestyle Author Dr Anna O’Donovan

About Dr. Anna O’Donovan – Medical & Lifestyle Author

Anna is a mum of three children, one with allergies, and she suffers from allergies and asthma herself. She is a qualified doctor and worked as a General Practitioner and as a dentist for a number of years. She is also an award-winning author.


air care, indoor air, asthma, asthma triggers, allergy, allergy triggers, healthier home, HEPA, air cleaner, air purifier, air filter

Further Reading 

Air Purifier Maintenance, Sylvane, Click Here

Air Purifiers: The Good, The Bad, and the Ugly. Click here

8 Best Air Purifiers For Your Home, Forbes, Click here

Related Internal Links


What is an appropriate and effective filtration technology for a healthy indoor environment?

Taking care of the air we breathe is the most fundamental part of taking a proactive approach to a healthy environment. For many people the health risks posed by the indoor air environment can often be significantly higher than outdoor air. Particles released by cooking and burning fuel, volatile chemicals emitting from paint and cleaning products as well as allergenic particles such as animal dander, pollen, mold and dust mite particles, can all impact negatively on a healthy indoor air environment. Poor indoor air quality can be particularly harmful to vulnerable groups such as the very young and old, and those suffering from chronic respiratory diseases. 

Fortunately there are a number of approaches that can be taken to improve and maintain the quality of your indoor air. A number of these focus on the removal of particulates from the air by passing them through some kind of filter, and can be called air filters or air purifiers. In general these terms are used interchangeably, however air purifiers generally have more than one mode of filtration.

Indoor Air Quality in the Home by Dr. Anna O'Donovan, Allergy Standards

Modes of Filtration

Air cleaners or air purifiers are designed to remove particulates and sometimes odors from the air we breathe. There are a number of different ways that they can do this.

  1. Media based filter: Filters are generally ranked according to the particle size that they will trap. In line with this, the smaller the particle size, the more power that is required to draw air through the filter. Over time filters will need to be replaced as they become clogged and, in a similar way to vacuum cleaners, the exposure of a sensitive individual needs to be considered when establishing a removal and replacement protocol. The efficacy of a filter is dependent upon the integrity of the seals into which it is placed and you should ensure that replacement of filters does not result in compromising the filter system. Dependent upon how effective a filter is, it may be described as a HEPA filter (high energy particulate air).
  2. Electrostatic filters: electrostatic filters work on the basis of electric charge. As the particles in the air pass through the electrostatic filter, they receive a charge, this allows them to be stuck to metal plates in the air filter, preventing them from being released out of the air purifier. The principle of electrostatic filtration can also be applied to media based filters, giving them an added advantage for filtration.
  3. Activated carbon filters: these filters are made of porous carbon. As odors and gases pass through the carbon filter, they become trapped in the pores, unable to pass through. The pores may become clogged over time and will then need to be replaced.
  4. UV light: UV light is capable of killing micro-organisms, UV light sources can sometimes be present in room air cleaners, and also in HVAC systems. UV light requires time to kill micro-organisms, it doesn’t happen immediately. As such, where a UV system is in place, you should make sure that it actually is effective, rather than just being a sales pitch!

In addition to the type of filtration system selected, you should ensure that the air cleaner that you select is powerful enough for the size of room in which it is to be operated. A useful way to determine this is by an air cleaner’s CADR rating. CADR, or Clean Air Delivery Rate is the performance metric to indicate the effectiveness of an air cleaner. If you purchase an air cleaner with a CADR rating too low for your room, you will find it ineffective.

While CADR is a key measurement for selecting an air cleaner, MERV (minimum efficiency reporting value) is important for selecting the right filter. The MERV rating is a measure of the size of particle that the filter will remove; HEPA filters are normally rated MERV 13. The below chart is a useful guide:


Air-Cleaners-Allergy-Standards-Healthy-Indoor-EnvironmentWhile CADR and MERV are useful tools to assist in selecting an appropriate air cleaner, you should also consider the environment in which it is to operate. Your indoor air is very much a function of your outdoor air and so if you live in an area with high environmental particulate load, this will transfer to your indoor environment. This will impact how often you need to change your filter, and how long you need to leave your air cleaner on for. An example of this is the recent tragedy of the wildfires in California, smoke from these fires can contain a wide range of particles at very small size, down as low as 0.4 micron. Carbon monoxide, a dangerous gas, can also be produced during fires and so precautions that could be followed in the home would be the use of an air cleaner with a media based HEPA filter (to capture particles as low as 0.3 micron) and some type of carbon or zeolite filter to capture any gases that may enter the indoor environment. Due to the high load in the air following these fires, filters would need to be changed more regularly and air intake should be set to re-circulate rather than using fresh air intake.

PM2.5 Vs PM10

When discussing air pollution, the terms ‘PM2.5’ and ‘PM10’ are often used. PM stands for particulate matter and the number that follows it refers to the size of the particulate matter in microns. A micron is one thousandth of a millimetre, for comparison, the period at the end of this sentence is about 400 microns! Although both these types of particles are very small, PM2.5 are referred to as ‘fine particles’ and PM10 as ‘coarse particles’ (as they are larger). The primary sources of these particles are cooking, automobile emissions, dust and incomplete combustion (fires). When particles are inhaled, larger particles are normally captured by the hairs in the nose, however particles of size less than PM10 can bypass this defence. The smaller the particle, the deeper it can make its way into the respiratory system, and potentially the more damage it can cause. Particles that are defined as PM10 include dust, pollen and sea salt, particles defined as PM2.5 are generally particles emitted from fossil fuel burning such as coal, wood, rubber and other materials.

Certain parts of the population are more susceptible to particle pollution:

  • Children
    • Lungs still developing
  • Senior Citizens
    • May have undiagnosed heart or lung conditions
  • People with existing heart or lung diseases
    • Particle pollution exacerbates these conditions
  • People who exercise or breathe outdoors
    • Breathe faster and deeper than sedentary adults

While these particles are very small, their impact on the economy can be large – air pollution in the US on average costs between $40-50 billion and 50,000-120,000 premature deaths are associated with exposure to air pollution.

Other methods of air purification:

Ionizers and Ozone generators: while these produce different types of molecules, they work in a similar way. They produce ions or ozone which is released from the air cleaner/purifier to be distributed around the room. Allergenic particles normally floating around a room have a neutral or no charge, when they come into contact with ions or ozone, they become charged and can stick to surfaces around the home, removing them from the air. They can then be removed from these surfaces by normal day to day cleaning.


Ozone (O3) is a gas that is highly reactive, it can be formed naturally or as a result of human activity. The ozone layer in the atmosphere is formed naturally through the interaction of solar ultraviolet light with oxygen (O2). In the ozone layer, ozone has a highly protective role – it absorbs UV light and prevents excessive exposure of humans to harmful UV rays. If ozone is inhaled however, it can have a number of harmful effects. It can be transported all the way to the lower respiratory tract where it can interact with biological molecules in the lung to cause:

  • Cough
  • Throat Irritation
  • Pain or discomfort in the chest when breathing
  • Chest tightness or wheezing

For the general population this is not very comfortable, for those already suffering from lung problems, such as asthma, it can have a significantly harmful effect.

Many electrical implements (including air cleaners) produce ozone as a by-product of functioning, and this cannot be avoided. All electrical implements are tested for the ozone levels that they produce to ensure that they aren’t produced at harmful levels (greater than 0.05 parts per million). As such, an air cleaner that relies on ozone as an air purification function could not be recommended.


Ionizers release ions into the environment. Ions can be positively or negatively charged and their main function in air cleaning is to pass their charge onto neutral air particles. By passing on this charge, it causes the particles in the air to stick to surfaces, thereby removing them from the breathing zone. Research in the area of negative ions supports the safety of these ions, however there is not as much research performed on positive ions. Anecdotal, unsupported research indicates that positive ions may have a detrimental impact on health. Air cleaners with an ionising function must therefore produce predominantly negative ions to comply with certification. 

Certification of Air Cleaners and Purifiers

Selection of the right air cleaner or purifier can be difficult, and there are a number of Certification Marks that can help you make the right selection.

clean-air-delivery-air-aham-sealCADR – The Association of Home Appliance Manufacturers (AHAM), established more than 50 years ago, represents the appliance manufacturing industry by through leadership, education and advocacy. Part of this role involves setting standards for the performance of these appliances, including air cleaners and filters. The standard for determining this is the Clean Air Delivery Rate (CADR). This measure defines the amount of clean air that an air cleaner delivers, based on scores for smoke, pollen and dust. The higher the CADR, the faster the rate of air cleaning. This CADR number, as mentioned above can be used to determine the size of room that the air cleaner is suitable for; the CADR of your air filter should be equal to at least two-thirds of the room’s area.


European Centre for Allergy Research Foundation allergy test

European Centre for Allergy Research Foundation allergy test

ECARF – The European Centre for Allergy Research Foundation (ECARF) is a not for profit foundation that certifies products based on specific testing standards. ECARF certifies a range of consumer products, including air cleaners/purifiers. These are tested based on removal of both fine and coarse indicator particulates that would represent the size of bacteria, pollen, spores as well as much smaller particulates. The standard also allows for testing of ozone and noise emission.


asthma & allergy friendly® Certification program USA

asthma & allergy friendly® Certification program

asthma & allergy friendly®– The asthma and allergy friendly® Certification Program is operated by Allergy Standards in collaboration with the Asthma and Allergy Foundation of America (AAFA), Asthma Canada (AC) and is also operated internationally through a global certification mark. Air Cleaner/Purifier certification is based on the impact on the indoor environment for those suffering from asthma and allergies. The standard measures for the performance of air cleaners/purifiers against real dust and allergens (cat, dust mite and pollen) and the air cleaner is measured in a room sized chamber in order to ensure that the air cleaner actually removes the allergen, rather than just re-distributing it. In addition to the use of real allergen, the asthma & allergy friendly® testing also includes room disturbance as part of its test protocol, to simulate testing of the air cleaner under real life conditions. Validation of ozone emissions is also part of this testing standard. While media based air filtration forms the main part of certification, other types of air cleaning are also considered, including ionizers.


Sick building syndrome Indoor Air Quality Allergy StandardsAir cleaners or purifiers play an essential role in maintaining a healthy indoor air environment. However selection of the right air cleaner, with the appropriate effective filtration technology is essential. Filter efficiency, size of room, outdoor environment and alternative technologies are all things that need to be considered. It is important that prior to purchase of an air cleaner or air purifier for your home, that you educate yourself as much as possible in order to make the right choice!







Dr. Tim Yeomans photo

Dr. Tim Yeomans

About the author 

Thanks to Dr. Tim Yeomans for this insightful article.

Dr. Tim Yeomans is the Centre Manager for Shannon Applied Biotechnology Centre, a collaboration between two third level colleges in Ireland. Tim holds a PhD in Microbiology and postgraduate qualifications in Technology Commercialisation and Innovation Management. Tim has worked in research and development for 20 years, both in industry and academia. In his role in Shannon ABC, Tim is responsible for the scientific direction of the Centre, intellectual property management and business and technology development.


air care, air purifier, air cleaner, ioniser, ozone, HEPA, indoor environment, allergy, asthma, certification, allergy insights, healthier home, indoor air quality.

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