Things to consider before selecting an air cleaner?
How do I know which air cleaners are really effective?
Why is air cleaner efficiency measured at 0.3 micron?
Particles captured by various types of air filters and cleaners
What is a true HEPA filter?
Electronic precipitation
HEPA vs Electronic
How is air cleaner performance measured?
Why Honeywell recommends 6 air changes per hour
What is ozone?
How can you measure sound?
clean air delivery rate
what is the difference between 95%, 99% and 99.97% efficiency?
what about ionizers?

Things to consider before selecting an air cleaner?

   1.      What is the efficiency of the air cleaner vs particle size?
   2.      How many air changes per hour are necessary?
   3.      What is the effectiveness of the air cleaner?  Does the air cleaner improve the air distribution pattern in the space?
   4.      What service and maintenance options are available?
   5.      What is the life expectancy of the product?

How do I know which air cleaners are really effective?

The Clean Air Delivery Rate (CADR) is the standard by which portable room air cleaners are evaluated.  You will generally see CADRs expressed for the three most common types of pollutants: TOBACCO SMOKE, DUST and POLLEN.  CADR refers to the amount of clean air provided by an air cleaner each minute of operation - measured in cubic feet.

Why measure efficiency at 0.3 micron?

Media air cleaners are rated accordingly to their ability to capture particles 0.3 microns in size.  Why?  Because these particles are the most difficult to remove from the air.


In standard tests using dioctyl phthalate (D.O.P.) which generates 0.3 micron particles when tested, Honeywell® hospital grade filters were rated at 95% efficiency³ and HEPA filters at 99.97% efficiency.

But these are minimum ratings.  The laws of physics make Honeywell® air filters actually more efficient on particles smaller or larger than 0.3 microns.  And these high efficiencies are maintained over the life of the filter.

How small is 0.3 microns?

Very small!  For comparison, household dust is 10 microns, a tobacco smoke particle is about 1 micron, and cat dander 5 microns.  Pollen and mould spores are 30 microns in size, with a human hair at 40 microns.  Remember, particles less than 10 microns in size are not visible to the human eye, but they are present in the air and can cause irritation.  Honeywell True HEPA models help filter these pollutants from the air passing through the filter returning cleaner, fresher air to you.







(1 micron = 1/25,000 inch)

Atmospheric Dust


Cooking Grease


Pet Dander


Tobacco Smoke

Particles captured by various types of air filters and cleaners


Particles captured by

a standard disposable

furnace filter

particles captured

by a Honeywell

media air filter

particles captured

by a Honeywell

electronic air cleaner

or portable HEPA

room air cleaner
Gases* (molecules)

that can't be

captured by

air filters

human hair
large and medium-

sized bacteria
very small bacteria

dust mites
larger dust mite

debris (e.g.

carcass parts)
fine dust mite debris

whole pollen
broken pollen grains
nitrous oxide

human skin flakes
carbon particles

larger animal dander
fine animal dander
medium to fine

tobacco smoke


larger household

dust and lint
medium household

dust particles
medium to fine

cooking grease and

smoke particles

larger soil

dust particles
fine soil

dust particles
fine household dust
general odours

(all odours

are gases)


dust particles
medium to fine

wood smoke

carbon monoxide

larger tobacco

smoke particles
carbon dioxide

larger wood

smoke particles

larger cooking

grease and

smoke particles

* no air cleaner can remove gases.  Options for reducing gas levels are: 1) eliminating or reducing the source; 2) absorption, such as a filter made of activated carbon or alumina; and 3) diluting the indoor air with ventilation.

What is a True HEPA filter?

HEPA, an acronym for High Efficiency Particulate Air, is an air cleaning technology first developed during the early days of atomic research to clean the air of radioactive particles that might escape and create a health hazard for researchers.


Today, True HEPA filters are commonly used in medical laboratories and commercial applications where totally clean air environments are needed for human health and safety.  enviracaire® Portable Air Cleaners bring this technology to the home and office.


True HEPA air filtration is featured in all enviracaire® Portable Air Cleaners.  True HEPA filtration is recognized as the most efficient media, capable of removing sub-micron sized particles from the air (at least 99.97% at 0.3 micron size).*


HEPA filters are recognized as one of the most efficient ways known to remove airborne particles. They are used in medical, laboratory, and commercial applications where clean room environments are required.

Honeywell® air cleaners utilize true HEPA filters. Plus Honeywell's SurroundSeal® HEPA filter technology helps assure that virtually all of the air drawn into the air cleaner passes through the HEPA filter.

* Overall particle reduction depends on many factors including the amount of air processed, the pollutant type and the pollutants' introduction rate into the environment.


What is a HEPA filter made with?

The filtering material or media is made of very thin glass fibres.  The glass fibres are made into paper, much the same way as cellulose or wood fibres are used to make paper.  In thickness and texture, the HEPA media is similar to blotting paper.  Air cannot easily get through the dense paper, so a very large area of paper must be used to permit filtering of a significant volume of air.  To get a large area of the media into the filter, it is pleated, creating an "extended surface".


For example, an enviracaire® True HEPA filter measuring 60 cm can contain as much as 12 square metres of filter media for maximum cleaning efficiency.

How does a HEPA filter work?

Basically, as particles pass through the densely packed glass fibres of the paper media, they literally run into one of the fibres and stick to it by mutual attraction.  On a large scale, it would be like trying to blow a grain of sand through a stack of hay.

What are "HEPA-type" filters?

"Hepa-type" filters may look like True HEPA filters and be made the same way.  Even the paper media is made of the same glass fibres.  But, the number and density of the fibres is less, so that allergens and pollutant particles get through.  "HEPA-type" filters are available in many different efficiencies, the best being only about 95 percent effective.  This is below the minimum efficiency required to be a True HEPA filter.  All enviracaire® Portable Air Cleaners feature True HEPA filtration.


What is the purpose of the prefilter in the Portable Air Cleaners?

The prefilter is a polyester-based activated carbon mixture and absorbs odours.  It should be replaced every 60 to 90 days, or whenever the unit emits a persistent unpleasant odour.  This odour indicates that the absorptive capacity of the carbon has been used up.  Washing will not restore its ability to absorb or remove odours.

Electronic precipitation

The scientific name for the air cleaning process used by electronic air cleaners is two-stage "electronic precipitation".

· most particles caught by the prefilter screen.

· smaller particles flow through the screen to the first section of the cell.  As they pass through a series of high-voltage ionizing wires - more than 7,000 volts - and become electrically charged.

· charged particles continue through the cell to the collecting screen.

· these particles stick like magnets to a series of plates with opposite electrical charges.

· the electronically cleaned air is drawn into the system to be heated or cooled before being circulated around your home.


Independent testing shows that Honeywell® Electronic Air Cleaners capture a very high percentage of mould spores, bacteria, dust mite antigen, cat dander and ragweed pollen from the air that passes through the filter. The Honeywell® Electronic Air Cleaner captured more than 90% of mould spores and ragweed pollen from the air passing through the air cleaner, more than 70% of bacteria and cat dander, and nearly 60% of dust mite antigen.


The testing found that the Honeywell® Electronic Air Cleaner is more efficient at capturing all five types of particles than a standard 1-inch furnace filter.

  An air cleaner may provide some relief to individuals suffering from allergies or other respiratory problems, and should be part of an overall allergy treatment program. However, there is no guarantee that a reduction in symptoms will occur through the use of any type of air cleaner.

HEPA vs Electronic

There have certainly been many misconceptions regarding the efficiency's of Hepa and Electronic filtration. Here are the FACTS!!!!!!!!!!!!


Filtration systems are typically measured at how effective they are at removing airborne contaminants of a certain size. The size of a particle, whether it is a mould spore, a dust mite or just a particle of dust is measured as a micron. A micron is one millionth of a meter, 0.00004 inches. As an example, a human hair is 100 microns in size. The majority of airborne contaminants that affect us the most are not visible by the human eye. That's why you purchased an Air Cleaner!



A true Hepa filter is rated at 99.97% efficient at a particle size of 0.3 microns. This is extremely efficient, however how effective is a Hepa air cleaner at removing particles that are smaller than 0.3 microns? A Hepa filter is actually more efficient at removing particles that are smaller than 0.3 micron. The reasoning behind this is that of all the independent studies showed that a particle measured at 0.3 microns was the most difficult size to capture.



Electronic air cleaners or Electrostatic Precipitators are 72% efficient at removing particles that are 0.3 microns in size. This form of filtration is still very effective at eliminating airborne contaminants. In many cases you will see an Electronic Air Cleaner with a rating of 95% efficient at a particle size of 0.01 micron.


An electronic air cleaner's effectiveness at removing airborne contaminants is very close to any True Hepa air cleaner. Both are highly effective at improving your air quality at home or at work.


So...if you have purchased an Electronic or a Hepa Air Cleaner, you can certainly breathe a sigh of relief!

How is air cleaner performance measured?

No single test is used industry-wide to rate cleaner efficiency.  Manufacturers choose from five tests, each measuring efficiency in a  different way.  That's part of the reason why it's difficult to compare manufacturer's efficiency ratings.  It's a little like the familiar comparison of apples to oranges.  Unless the same test was applied to both units, you'll be able to tell that both are fruits but that's about it.


That last statement is worth emphasizing for the record - you simply can't make a meaningful comparison of air cleaning efficiency unless both units were subjected to the same test.  Period.


A brief description of the top three tests used to measure air cleaner efficiency:



An air cleaner is mounted in a clean test duct with highly efficient filters mounted upstream and downstream from it.  Outdoor air is then introduced into the duct.  The upstream filter catches a sample of airborne particles before they reach the air cleaner, providing a benchmark for later comparison with the downstream filter and establish an efficiency rating.  This test measures initial efficiency - efficiency when the air cleaner is new or just cleaned.


Test procedures are identical to the Initial Atmospheric Dust Spot Test except that the same air cleaner is used for several test runs (and is not cleaned between runs).  An average of all test runs is computed to arrive at average efficiency.


Test procedures are similar to the above, but this test measures an air cleaner's ability to remove particles of a uniform size.  Usually the particles tested against are 1 micron or larger in diameter.  These uniform-sized particles represent only a fraction of those normally present in the air, thus the name "fractional efficiency."

Why Honeywell® recommends 6 air changes per hour?

The degree to which air quality is improved is strongly influenced by the number of air changes per hour (ACH) achieved by the unit.  Air is cleaned by constant circulation through the air cleaner, and the ACH is: volume of air to be treated in the room divided by the volume of air passing through the air filter.  Therefore, in choosing the right system for your needs, the size of the room as well as the capacity of the air cleaner must be considered.


The enviracaire® series of True HEPA air cleaners provides a choice of units which will deliver the air-cleaner efficiency for your needs:


· 4 to 5 ACH

Research has demonstrated that recirculating or changing the air in the room four to five times per hour with a high efficiency True HEPA filter will cut airborne contaminants in half (50 percent), resulting in good air quality improvement.  This is the minimum recommended air circulation for allergy sufferers.


· 6 to 7 ACH

Changing the air in the room six to seven times per hour will yield a 70 percent reduction in contaminant levels, and result in noticeable relief from many allergy symptoms and seasonal respiratory problems.  Expect excellent air quality improvement.


· 8-Plus ACH

Changing the air in a room eight or more times per hour yields a dramatic 85 percent reduction in contaminant levels, resulting in noticeable symptom relief from severe allergies asthma and other chronic respiratory problems.  Expect superior air quality improvement.

What is Ozone?

Ozone is a colorless gas that occurs naturally in the atmosphere. It is particularly reactive and relatively unstable. The ozone molecule contains three oxygen atoms whereas the oxygen molecule contains only two. Ozone is normally made from oxygen, either from oxygen in the air or from high purity oxygen gas or mixtures thereof, and it reverts to oxygen upon decomposition.


Formation: The formation of ozone from oxygen requires an input of energy into the oxygen molecule by some method. This process is achieved by an electric discharge field as in the corona discharge (CD type) ozone generators or by ultraviolet (UV) radiation as in UV type ozone generators or as occurs in nature in the upper atmosphere by natural UV radiation. Ozone also may be made through electrolytic and chemical reactions.


Ozone in nature: The ozone layer of the upper atmosphere at the altitude of 20,000 - 30,000 meters forms a natural barrier to protect all living species on earth from the harmful and powerful ultraviolet radiation of the sun. The beneficial effect of the ozone layer is considered to be so important that the manufacture and use of certain chemicals, such as chlorofluorocarbon spray can propellants, are prohibited in some countries. When discharged into the air, these chemicals find their way to the upper atmosphere and destroy or diminish the ozone layer. For this reason, an international effort is underway to limit the production of chlorofluorocarbon propellants worldwide.


In the atmosphere at ground level ozone is formed by the reaction of hydrocarbon pollutants in the air and atmospheric oxygen under the influence of sunlight. The amount of ozone so produced serves to indicate the extent of hydrocarbon pollution or smog in the air.


Common Applications: Ozone is a very powerful chemical oxidizing agent and a very powerful disinfectant. It has the unique feature of decomposing to a harmless, non-toxic, environmentally safe material being oxygen. These characteristics make ozone exceptionally suitable for the treatment of drinking water, wastewater and for the disinfections of high purity de-ionized water used in the pharmaceutical industry and in the manufacturing of integrated circuits in the electronics industry.

How can you measure sound?

Sound can be measured in Sones.  Sones take into account a sound's loudness (measured in decibels) and its frequency (how high or low it sounds) as perceived by the human ear.  This is important because the human ear hears sound differently than do sound measuring devices, as certain frequencies of sound are more pleasant for us to hear than others.  Using Sones, it is easy to compare how loud an appliance is against another - a Sone of 10 is half as loud as a Sone of 20.  The American National Standards Institute standard, ANSI-S12.31-1990 is most suitable for measuring the sound of small appliances.

Clean Air Delivery Rate

The Clean Air Delivery Rate (CADR) is the standard by which portable room air cleaners are evaluated.  You will generally see CADRs expressed for the three most common type of pollutants: TOBACCO SMOKE, DUST and POLLEN.  CADR refers to the amount of clean air provided by an air cleaner each minute of operation - measured in cubic feet.

From air cleaner to air cleaner, compare the CADR numbers.  First, look at suggested room size, then refer to the Clean Air Delivery Rate numbers.  The higher the numbers, the faster the unit filters the air.
485AI     240     50     80     100
585AI     320     60     60     130
790AI     644     150     200     260
985AI     840     150     250     350
13520     287     275     287     251
17000     130     130     130     130
17200     170     170     170     170
17400     220     200     220     180
18150     150     150     150     135
50250     250     250     250     250
60001     230     150     120     120
C90A     465     300     325     365

Room size ratings conform to the Association of Home Appliance Manufacturers Certification Program criteria of 80% smoke reduction.  Higher Clean Air Delivery Rates provide improved performance in all room sizes.  Portable air cleaners will be much more effective in rooms where all doors and windows are closed.

What is the difference between 95%, 99% or 99.97% efficiency?

The Honeywell TRUE Hepa filter minimum efficiency is 99.97% at 0.3 microns (from the air that passes through the filter).  Particles that are larger or smaller than 0.3 microns are captured at that efficiency or higher.  99.97% of all particles that go through the filter are captured at a minimum.

A filter that is 95% or 99% efficient will not filter as many airborne particles that are 0.3 microns.  This may not seem much, but if the air containing 1,000 particles at 0.3 microns in size enters the Honeywell® True HEPA filter, only three particles will pass through while a 95% filter will allow over 50 particles to pass through.

What about ionizers?

Ionizing models do collect some airborne particles and help freshen the air, but for improved removal of airborne allergens and particles, a True HEPA filter with 99.97% helps clean the air that passes through it at a higher rate.  Most allergists do not recommend using indoor ionizers in treatments for their patients.

Glossary of terms
CPZ Sorbent Media
Material that captures up to 50% of its weight in gases, odours, vapours and volatile organic compounds (VOCs).
D.O.P. (Dioctyl Phthalate)
A compound used to test air cleaner efficiency.  When heated, it consistently generates particles about 0.3 microns in size.
A unit of measurement equal to one millionth of a meter, or about 0.00003937 inches.  (By comparison, a human hair is 100 microns in diameter).
HEPA (High Efficiency Particulate Air)
A filter rated at a minimum 99.97% D.O.P. efficiency¹ on 0.3 micron particle.
95% D.O.P. Hospital-grade Filter
A filter rated at a minimum 95% D.O.P. efficiency³ on 0.3 micron particles.  Primarily used in combination with sorbent media.
VOCs (Volatile Organic Compounds)
Gases created by the use of chemical solvents and other carbon compounds used in enclosed spaces.  Associated with unpleasant odours, and frequently with "sick building syndrome".
Coanda Airflow
An air circulation pattern using multiple air intake and air discharge vents.


¹,³ 99.97% efficiency ratings for HEPA (High Efficiency Particulate Air) filters and 95% efficiency rating for hospital-grade media filters are based on results from industry  standard tests using dioctyl phthalate (D.O.P.), which generates 0.3 micron particles when heated.

The amount of air moved through the air cleaner depends on the fan speed setting, room layout, and the placement of objects in the room that may affect air circulation.  Only air actually passing through the unit is filtered.  The rate of particle removal may be affected by the pollutant type, and the rate at which new pollutants are introduced into the air.  Odours are reduced only when using optional CPZ™ cartridge.


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