Is A HEPA Filter Really Necessary?
Should you choose a HEPA filter over other alternatives?At
first glance there may seem to be added expense in your initial
purchase. You may feel that replacement filters will expensive and
cumbersome. With so many air cleaners promising to be “silent” or have
“no messy, expensive filters” you might feel that HEPA filter air
purifiers are a second rate option. Is the marketing of well-heeled
consumer product companies really doing justice to this mainstay of air
purification? I feel that many people are being misled by the
disinformation of irresponsible marketing campaigns. That is one of the
reasons for building this site. Multiple chemical sensitivity, allergy
and asthma are problems I am personally familiar with. So finding
effective air purification systems has been a priority in my life for
the last fourteen years. Ultimately I came to the conclusion
that a HEPA air filtration system is the best solution available. I
believe that you too will benefit from a HEPA air cleaner. To explain why let’s start with the most basic questions you should ask when deciding on an air purifier.
Questions you should ask of any air purifier
- What will the air cleaner remove from your home air? What will it not?
- What is the efficiency rating of the air cleaner? How effective is the technology it uses to clean the air?
- Will
the air purifier clean the air in a room as large as you need? How many
air changes per hour will it provide in that size room?
- How
easy or difficult is it to change or clean the filter? How often is
this maintenance necessary? How much do filters cost? Are they readily
available?
- How much noise does the filtration system make? Is it quiet enough to run while you sleep?
With these questions in mind, how effectively does HEPA air filtration give the results you’ll be most satisfied with?
Evaluating HEPA air filtration
What will a HEPA filter remove from your home air? What will it not?HEPA
filters trap allergy-causing particles like pollen, pet dander and dust
mites. They also capture irritant particles like tobacco smoke. Usually
some form of prefilter is used to trap larger dust particles that would
prematurely clog the higher efficiency HEPA filter placed after it. HEPA filters will not remove chemicals and odors. This is why they are often combined with activated carbon filters. Of
course, all filtering systems likewise claim to remove such particles.
They likewise need to be supplemented in some way to remove odors and
chemicals. The real advantage of HEPA air filtration is seen in its
overall effectiveness versus these other air cleaners. What is the efficiency rating of HEPA? How effective is the technology versus other air cleaning systems? Only
HEPA air filtration meets a standard recognized by government and
industry. To receive the HEPA designation it must remove 99.97% of all
particles as small as 0.3 micron in size. While other filter
media remove some particles at that size their efficiency varies and is
often no greater than 50%. Even much larger particles like pollen may
not be fully removed. The problem with non-HEPA filters is you have no
way of knowing how effective they are. Ion generators do not
remove particles at all. Their method is to fill the air with charged
particles that tend to attract other particles. These stick together
and presumably settle out of the air more quickly. Some charged
particles will stick to the walls and furnishings. This has been called
the “black wall effect”. The EPA has expressed concern that these
uncollected charged particles may even deposit within the lungs of
exposed persons. Ionic air cleaners that use collector plates
are called electrostatic precipitators. Their efficiency at particle
collection tends to be no greater than 80%, much less than HEPA air
filtration. Studies have shown that the collection efficiency can be
reduced to as little as 20% in as few as three days due to particle
loading of the collector plates. Some people claim that ozone
generators clean the air by destroying the contaminants. Scientific
studies have shown this to clearly not be the case. Ozone can react
with pollutants but the partial breakdown byproducts that result can be
more numerous and more dangerous than the original pollutants. Ozone
generators’ efficiency at removing contaminants is essentially zero. If you really want the most effective air cleaning available then HEPA air filtration is your best choice. Will
the air purifier clean the air in a room as large as you need? How many
air changes per hour will it provide in that size room? HEPA air filtration is the most effective means to clean large volumes of air rapidly. Of
course, these air purifiers come in a wide variety of sizes allowing
you to choose according to your needs. Some Allerair air cleaners
reportedly cover areas as large as 1800 sq. ft. However, that is at a
reduced number of air changes per hour. Even so, the total capacity of
these fan forced air cleaners is always far greater than other systems. In
ionic air cleaners that use no fan the speed of ionized air being
pulled through the unit is quite low. This means a very much-reduced
ability to clean large volumes of air. Where ionic air cleaners
have an added fan the air speed has to be kept low also. This is
because a fast moving air stream would not permit the charged particles
to be deflected onto the collector plates. Again, you don’t get the
ability to clean large volumes of air quickly. How easy or
difficult is it to change or clean the filter? How often is this
maintenance necessary? How much do filters cost? Are they readily
available? One of the greatest scams in the air purifier
market among non-HEPA air cleaners is to sell a cheap air purifier and
then bilk the customer later with pricey regular filter changes.
Sometimes the filters are hard to come by, either the store selling the
air cleaner doesn’t carry the filters or is chronically out of stock. The
actual cost of a replacement HEPA filter may seem high compared to a
non-HEPA filter. However, consider that replacement may be once every
two, five, even eight years in the case of the Allerair AirMedic. This
means the annual cost to have clean air is low by comparison. With
ionic air cleaners you avoid the cost of replacement filters but cannot
avoid the necessity of constant maintenance cleaning of the collection
system. Many owners have complained at how difficult it is to properly
clean closely spaced collector assemblies. A collector grid that isn’t
cleaned regularly doesn’t clean the air and can develop a residue on
the plates that will not come off. This permanently reduces its ability
to clean. HEPA air filters are very easy to change. Manufacturers
have made certain tools are never required and most can be completely
replaced in less than five minutes. All things considered, HEPA
air filtration is simple, easy, low maintenance and low in long term
cost while offering the best air cleaning possible. How much noise does the filtration system make? Is it quiet enough to run while you sleep? HEPA
air filtration tends to be the noisiest because of the fan forcing air
through the system. However, high quality HEPA air purifier
manufacturers recognize this and do their best to keep noise levels as
low as possible. All offer low speed settings that are quiet enough to
sleep without disturbance. If you choose the right size air
purifier it will be able to give sufficient air changes per hour at a
lower speed setting. This keeps noise low and gives you additional
cleaning capacity at a higher setting in the event it is needed, like
after a cooking mishap. Ionic air cleaners may have an edge in the “silence is golden” department, but this comes at the expense of performance. I encourage you to put greater value on air cleaning performance and choose HEPA air filtration. If
you would like to consider air purifiers from companies that keep your
needs in mind and offer truly effective and reliable air purification
IQAir, Allerair, Austin Air and BlueAir are among the best. Return to top of HEPA filter article.Return to Home Air Purifier Guide homepage.
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