Glossary of Terms
CADR
Although there is no universally accepted method for comparing air-cleaning
devices, several investigators of portable air-cleaning units have expressed
their results as a ”Clean Air Delivery Rate” or CADR. The CADR is the
product of the unit efficiency and the airflow rate, and is a measure of the
number of CFM of air it cleans of a specific material.
DOP
The DOP Military Standard is the standard set by the federal government to
rate particle reduction by HEPA filters. This test rates high-efficiency
filters by the percentage of 0.3 micron size particles of dioctylphthalate (DOP)
smoke they remove.
HEPA Filter
HEPA stands for High Efficiency Particulate Arrested Filter, and like the
name says, these filters are designed to remove 99.97% of all airborne
pollutants 0.3 microns or larger from the air that passes through the filter
(these include tobacco smoke, household dust and pollen).
CARBON
Carbon, the sixth most abundant element in the universe, has been known
since ancient times. Many natural substances of base materials are used to
make carbon. The most common of these are wood, coal, lignite, and coconut
shell. Amorphous carbon is formed when a material containing carbon is
burned without enough oxygen for it to burn completely.
ACTIVATED CARBON or AC
Activated carbon is the generic term used to describe a family of
carbonaceous adsorbents with a highly crystalline form and extensively
developed internal pore structure. Activation creates a fast internal pore
network and imparts certain surface chemistries (functional groups) inside
each particle. Thus activation gives carbon its unique filtering
characteristics.
PRE FILTER
A pre filter is the primary layer of filtration that collects large
particles before they reach the HEPA filter. Eliminating these larger
particles, dust and hair extends the life of your HEPA filter. Occasional
vacuuming of the exterior of the unit will help extend life of the filters.
Frequent pre filter changes will also prolong the HEPA filter life.
GAS ADSORPTION
When a gas or vapor is brought into contact with a solid, the solid takes up
part of it. The molecules that disappear from the gas either enter the
inside of the solid, or remain on the outside attached to the surface. The
former phenomenon is termed absorption (or dissolution) and the latter
adsorption.
PRECIPATATOR
There are many simple electronic devices that claim to clean the air in your
home by making negative ions and ozone. The claim is accurate–they do make
both ozone and negative ions, and they do clean the air in your home.
However, that’s not the whole story. First, ozone may have the “fresh”
smell that occurs after a thunderstorm (a potent producer of ozone), but
ozone is a powerful oxidizing agent and chemical irritant that’s
considered an environmental pollutant rather than a charming scent. The
manufacturers are taking a nuisance effect and touting it as a “valuable
feature.” Second, the negative charges emitted by these electronic devices
attach themselves to dust, ash, pollen, and smoke particles and cause those
particles to bind themselves to your walls and furniture. The air really
does become cleaner, but every surface in your home becomes dirtier as a
result.
OZONE
Ozone, a lung irritant, is produced indirectly by ion generators and some
other electronic air cleaners and directly by ozone generators. While
indirect ozone production is of concern, there is even greater concern with
the direct, and purposeful introduction of a lung irritant into indoor air.
There is no difference, despite some marketers’ claims, between ozone in
smog outdoors and ozone produced by these devices. Repeated exposure to
ozone pollution may cause permanent damage to the lungs. Even when ozone is
present in low levels, inhaling it triggers a variety of health problems
including chest pains, coughing, nausea, throat irritation, and congestion.
It also can worsen bronchitis, heart disease, emphysema, and asthma, and
reduce lung capacity.
MICRONS
A micron is a unit of length equal to 1 millionth of a meter or .000039th
(39 millionth) of an inch. Another name for micron is micrometer.
PM10
Particulate Matter Up to 10 Microns in Diameter (PM10)
The number 10 refers to the particle size measured in microns.
PM 10’s are widely considered the most dangerous to human health.
PARTICLE COUNT
A standard developed for measuring particulate matter in a pre defined area.
ELECTROSTATIC
Electrostatic units filter the air using static electricity have a static
charge on the filter to allow airborne particles to “stick” to the
filter, just like static-charged clothing sticks together.
IONISER
Ion generators act by charging the particles in a room so that they are
attracted to walls, floors, tabletops, draperies, occupants, etc. Abrasion
can result in these particles being re-suspended into the air. In some cases
these devices contain a collector to attract the charged particles back to
the unit. While ion generators may remove small particles (e.g., those in
tobacco smoke) from the indoor air, they do not remove gases or odors, and
may be relatively ineffective in removing large particles such as pollen and
house dust allergens. Although some have suggested that these devices
provide a benefit by rectifying a hypothesized ion imbalance, no controlled
studies have confirmed this effect.
MOULD SPORES
Moulds produce tiny spores to reproduce, just as plants produce seeds. Mould
spores waft through the indoor and outdoor air continually. When mould
spores land on a damp spot indoors, they may begin growing and digesting
whatever they are growing on in order to survive. There are moulds that can
grow on wood, paper, carpet, and foods. When excessive moisture or water
accumulates indoors, mould growth will often occur, particularly if the
moisture problem remains undiscovered or unaddressed. Moulds can trigger
asthma episodes in individuals with an allergic reaction to mould.
CLEANING CAPACITY
An air cleaner must constantly recirculate indoor air in order to
effectively reduce concentrations of airborne particulate contamination.
Cleaning the total volume of air contained within a room is the equivalent
of completely changing the air in that room. Air cleaner filtration capacity
is expressed as the number of air changes per hour (ACH). For air cleaners
of equivalent filter effectiveness, a higher ACH rating yields higher levels
of air quality improvement.