If you are reading this page the chances are you have been considering the purchase of something to purify the air in your bird room, maybe an Ioniser? The term Ioniser has become synonymous with air purification due to the technology having been around for so long, yet believe it or not Ioniser air filters are actually one of the lowest forms of air purification available today.
What is an Ioniser & What Does an Ioniser Do?
Ionisers or negative ion generators, work by creating a static charge around the airborne contaminants that are floating around your room. Once charged with static, these particles (dust, allergens, pet dander etc,) simply stick to the nearest surface they find. Your air feels fresh because the contaminants are no longer floating around in mid air, but the fact is those contaminants are now firmly stuck to many of the surfaces of the room such as the walls, furniture, carpets and table tops. This is why you often see a ring of black around the base of an ioniser when it has been moved.
Some Ionisers have ‘collection’ plates inside them. These are supposed to collect the charged particles for you to wash off when the plates get full. But in reality most of the particles have already stuck to the nearest surface in the room and very few actually make it all the way back to the Ioniser.
Is an Ioniser an effective form of air purification then?
In a word, no. Ultimately an Ioniser air filter does not remove any of the offending particles from the room, it simply deposits them onto a nearby surface. If you are seriously looking to improve the air quality in your home then you should be looking to remove the offending allergens and dust particles as opposed to just moving them around. The logical choice would be either a good quality Hepa Filter or possibly even an Air Steriliser.
If not an Ioniser, then what should I be looking for?
Well, depending upon what you want to remove from the air, your first thought should probably be a good quality HEPA Air Purifier. A decent HEPA Air Purifier will actually gather and remove over 99% of all airborne contaminants right down to 0.3 microns in diameter. In fact the best HEPA air purifiers like the ones manufactured by the Swedish company Blueair actually trap particles all the way down to 0.1 microns. That is quite remarkable when you consider that a human hair is about 100 microns in diameter!
What micron sizes are Airborne Allergens and Dust then?
Most common allergens like pollen, mould spores, pet dander and dust mite feces range from about 100 microns down to around 0.3 Microns and so are easily filtered out by a good HEPA air purifier. Some household dust, insecticide dust, fungi and bacteria can be as small as 0.01 and then right at the smallest end of the scale you have viruses and bacteria which can be as small as 0.001 micron. If you are concerned about micro-organisms like mould spores and also want to destroy all viruses and bacteria then you should consider an Air sterilizer like the Airfree models. These are totally silent and never need any maintenance or replacement air filters. They are not so good for large ‘visible’ dust particles, but are unbeatable for destroying the really nasty or even hazardous contaminants.
What is a HEPA air purifier ?
HEPA stands for High-Efficiency Particulate Air and is a part of most types of high-performance mechanical air purifiers. HEPA filtration may be combined with other filtration, such as gas absorbing filters or microorganism destruction systems. A HEPA filter actually consists of a web of glass fibres capable of trapping close to all sizes of particle pollution. HEPA filters are found in both fitted installations that combine ventilation, heating and air conditioning, and in portable air purifiers. But of course, HEPA air purifiers are not the only type of air purifier – there are also electrostatic systems and ionisers as well, which work in a different way.
A true HEPA filter is defined by meeting the specifications of the United States Department of Energy for DOE regulated applications. A true HEPA filter has to be able to remove 99.97% of airborne particles of size 0.3 micrometres diameter passing through it. A HEPA filter can, of course, remove particles bigger as well as smaller than this, but it is the 0.3-micrometre particles that are hardest to trap in the filter, so that is why these are the particles used to judge performance. Air purifiers labelled ‘HEPA-type’, ‘HEPA-like’, ‘HEPASilent’ or even ‘99%-HEPA’ will most likely not meet the same performance standards as a proper HEPA air purifier, but are most of the time just misleading terms of art that marketing departments come up with to increase sales.
How long have HEPA air purifiers been around?
During the late 1940s, the United States Army Chemical Corps and the United States Atomic Energy Commission developed the first HEPA filters. The main purpose was to protect against the spread of radioactive dust during the development of the atom bomb. These early HEPA air cleaners were rigid and unwieldy machines, quite unlike their modern counterparts. They actually contained asbestos imported from Africa or Bolivia. Concern over the health impact of asbestos led to the development of alternative materials. There were also concerns about leaks and defects in the filter, so again research was needed into a better HEPA filter material.
During the development of the atom bomb, HEPA technology was considered ‘top secret’ but, after the war, the government declassified the technology so it could be used in commercial and residential settings, as it is today.
How does a HEPA air purifier work?
The HEPA filter media is a specialised filter consisting of a folded mat of microscopic borosilicate glass fibres. It has three different modes of action, each of which acts best upon a different size of a particle. Interception deals with particles above 0.4 microns in size and involves the particle sticking to a fibre in the HEPA filter when it comes close to it. In impaction, which also mainly affects particles above 0.4 microns, the particle is blown towards the fibres by the airstream in which it is travelling. It then collides with the fibres and sticks fast to them. Finally, there is diffusion, which mainly affects smaller particles, of size below 0.1 microns. The particle collides with air molecules that throw it off course. Diffusion keeps the particle within the filter until it is captured by impaction or interception.
What about particles at around 0.3 microns? They are captured, but not as efficiently. The 0.3-micron ‘window’ is known as the most penetrating particle size (MPPS), because particles in this size range penetrate further into the mesh before being trapped than smaller and larger particles do. In fact, the ability of HEPA filters to capture particles of size 0.3 microns is actually used as a measure of its effectiveness. The DOP penetration test involves sending a test stream of particles of this size through the filter and using a particle counter to measure the particles in the ongoing stream and outgoing stream to see what proportion is removed by the filter.
Why is HEPA filtration considered the most reliable?
A HEPA air purifier basically uses the same principle as a spaghetti strainer – it holds back everything that is too big to fit through. The benefit of this kind of filtration is that it does not lose its filtration efficiency over time; a true HEPA filter becomes more efficient in filtering air pollution. The airflow delivery rate of an air purifier using mechanical filtration might decrease, but the filtration efficiency will increase. This makes mechanical HEPA filtration the most reliable filtration technology because you know that the air that goes through the filter is always cleaned at the same high rate, whereas technologies such as ionisation generally suffer from a significant loss in filtration efficiency over time.
As mentioned before, the term “HEPA” filtration is unfortunately not properly regulated. Every air purifier manufacturer can use the term “HEPA filtration” as they please. So look for test results and product reviews from an independent air purification expert before purchasing it.
What does a HEPA air purifier take out of the air?
A HEPA air purifier will remove airborne particles over a wide size range. Examples include:
- Mould spores – 100 – 2 microns
- Pollen grains – 100 – 0.25 microns
- House dust mite allergen – 25 – 0.1 microns
- Bacteria – 25 – 0.25 microns
- Pet dander – 10 – 0.1 microns
- Toner dust – 10 – 0.1 microns
- PM10 – 10 microns or less (PM = Particulate Matter)
- Second-hand smoke – 4 – 0.01 microns
- PM2.5 – 2.5 microns or less
- Viruses – 0.05 – 0.003 microns
- Ultrafine particles – 0.1 – 0.001 microns
How is HEPA performance judged?
First, be aware that efficiency and effectiveness, although they sound similar, are not the same thing when it comes to choosing a HEPA air purifier. Efficiency is usually given as a percentage and it is a measure of the ability of the air purifier to remove particles from the air passing through it. The effectiveness is a measure of the air purifier’s ability to reduce airborne particles in an occupied room.
Efficiency depends on both airflow rate through the purifier and on the particulate load.
Effectiveness depends upon efficiency, the amount of air being filtered, and the path the clean air follows after leaving the filter.
So a highly efficient filter could actually be quite ineffective if the amount of air it has to filter is large and the airflow rate low.
A number of methods have been developed to determine the efficiency of HEPA filters installed in heating, ventilation, and air conditioning (HVAC) but these are not necessarily applicable to HEPA filters in portable air cleaners. Tests can also be done using a particle counter, which is a laser-based device that can detect the density of particles in a room. Such tests are a very accurate way of measuring the impact that an air purifier has on a room’s air quality.
There is also a measure that has been developed by the Association of Home Appliance Manufacturers called the Clean Air Delivery Rate (CADR). Important to note here is that this is the Association of Manufacturers that have come together to develop a standard to test their own products – so by far not an as independent standard as we would like to see. Nevertheless, CADR is used by the Environmental Protection Agency and the Consumers Union to compare air purifiers. It gives measures only for dust, tobacco smoke, and pollen removal. CADR does not give you any information about the long-term performance of the air purifier (units are only tested for 120 seconds – yes, seconds. Not days or weeks as it should be). That means that some technologies – such as ionisation – can have a great CADR rating, even if the ioniser’s filtration efficiency would decreases by 80% within a couple of days or hours for example.
An air purifier fitted with a HEPA filter will primarily remove airborne particle pollution. It will only remove some of the gaseous pollutions, like Volatile Organic Compounds. To effectively remove gaseous pollution you will need a system that also incorporates high quality activated carbon which will absorb gases.
A drawback of true HEPA filtration is that the air purifiers tend to be larger than other air cleaners. The larger size of a true HEPA air cleaner is required in order to be able to provide the desired airflow rate. You should be sceptical of an air purifier that is very small because it is doubtful that a small unit will move enough air to make a significant difference in air quality – even in a very small room. We recommend that a unit should clean the given room at least twice an hour. If the air purifier’s filtration efficiency is low, several more air exchanges will be needed.
No air purifier removes settled particles or dust unless they become airborne again. That is why they are called ‘air purifiers’ and not ‘dust collectors’. So while an air purifier can effectively take contamination out of the air, it might not necessarily create a dust free environment (depending on the particle size that the dust consists off).
Is there evidence that a HEPA filter improves health?
Some of the most recent clinical studies are:
- Part of the Cincinnati Asthma Prevention Study showed that kids with asthma who were exposed to second-hand smoke benefited from the presence of a HEPA air purifier in their bedroom. Having a real HEPA filter installed led to nearly a 20% reduction in unscheduled asthma visits to the hospital.
- A recent study from researchers at Simon Fraser University, Burnaby, Canada, reveals how a HEPA filter both cuts PM-based indoor pollution and improves two significant markers for heart health. Forty-five healthy adults took part and their homes were monitored for two consecutive seven-day periods. During this time, one HEPA air purifier was placed in the main room and another HEPA filter in the participant’s bedroom. During one seven day period, the HEPA filters were operated normally and during the other, they were operated without the filters. Levels of C-reactive protein (CRP), a marker for inflammation and heart disease, went down 33% with the use of a HEPA filter.
- A study from Singapore General Hospital showed that installation of HEPA filters (an IQAir HealthPro) reduced the number of cases of invasive Aspergillosis, a potentially fatal fungal infection, by over 50%.
What are the main applications of a HEPA air purifier?
Modern HEPA air purifiers can be found in any industry or sector where airborne contamination can be an issue, such as healthcare, hospitality, office environments and manufacturing. In the home, portable air purifiers and vacuum cleaners fitted with HEPA filters can be used to remove dust containing house dust mite allergens, pet dander, pollen, mould, and traffic pollution which might otherwise provoke asthma or allergy symptoms.
What is the difference between a HEPA and a HyperHEPA air purifier?
The IQAir HyperHEPA filter can remove particles down to 0.003 microns in size with a guaranteed efficiency of more than 99.5%. This is 100 times smaller than the lower limit of other HEPA air purifiers and 10 times smaller than a virus. The significance is that the HyperHEPA filter operates on the nanoscale, dealing with the ultrafine particles which other air purifiers cannot remove. The smaller the particle, the further it can penetrate into the body and therefore the greater the potential health risk. The performance of the HyperHEPA can also help create the ultra-clean environments required in certain industry sectors.
Reference: Article taken from Internet Saturday, 27 February 2021 at 10:01