Clean
air is becoming more and more important in today’s world. People are concerned with cleaning outside
air and reducing pollution, cleaning inside air for the health and comfort of
individuals inside buildings, and finding energy efficient ways to clean
air. Having a basic understanding of air
filters and how they work can make the daunting task of purchasing a new air
filter a little easier.
To
learn more about air filters, click on the links below:
·
What is an air filter?
·
Why are air filters used?
·
What is a cleanroom?
·
Classifications of
cleanrooms
·
How air is filtered
·
Common particles
and their sizes
·
Choosing the right
filter
What is an air filter?
An
air filter is a device that cleans air.
It removes contaminants such as dust, mold, and bacteria from the
air. (See How air is filtered)
Air
filters are constructed of filter media, sealants, a frame, and sometimes a
faceguard and/or gasket.
o
Media is the filtering material. Common types of media include glass fiber,
synthetic fiber, non-woven fiber, and PTFE.
o
Sealant is the adhesive material that creates a
leak-proof seal between the filter media and the frame.
o
Frame is where the filter media
is inserted. It can be made from a
variety of materials including aluminum, stainless steel, plastic or wood.
o
Faceguard is a screen attached to the filter to protect
the filter media during handling and installation.
o
Gasket is a rubber or sponge like material used to
prevent air leaks between the filter and its housing by compressing the two
together.
Air
enters the filter through the upstream side. It flows through the filter, contaminants are
taken out of the air, and the ‘clean’ air exits through the downstream
side. How ‘clean’ the air is on the
downstream side depends on the efficiency of the filter
Efficiency is the filter’s
ability to remove particles from the air.
Different applications require different levels of efficiency. (See Common particles and their sizes
or Choosing the right filter).
How air is
filtered
There
are three types of air filters: mechanical, electrostically charged filter
media, and electronic air cleaners.
Mechanical filters remove dust and particles by capturing them on the
filter media. Fibers of electrostatically charged filter media are charged to increase
the filter efficiency. Electronic air
cleaners attract charged particles to oppositely charged collectors.
Cambridge
Filter manufactures mechanical filters. Air
is filtered using one of three methods: inertia,
interception, or diffusion.
Air filters in use
o
Public Buildings
§
Outside air is brought into the building, filtered, and
circulated throughout the building.
Smog, dust, pollen and other particles are filtered out to create a
comfortable and healthy environment for people inside. As public awareness increases, Indoor Air
Quality (IAQ) is becoming more important.
Poor IAQ can lead to sick building
syndrome (symptoms include headaches, eye irritation, and fatigue) which
can lead to discomfort and low productivity.
§
Government buildings are using more efficient filters not only
to improve IAQ, but also to help protect people from the threat of
bioterrorism, such as anthrax.
o
Medical Facilities
§
Hospitals and clinics use high efficient filters to prevent the
spread of infectious diseases. Clean air
is especially important in operating rooms, intensive care units, and other
critical care areas. Enzymic filters are
also used because of their ability to capture bacteria and actually destroy it.
o
Food Industry
§
Facilities require clean air to prevent contamination and to
ensure the food being processed and packaged is safe for consumers.
o
Critical Manufacturing
§
Industries such as pharmaceutical, microelectronics, and
research laboratories require super clean air for their manufacturing
processes. One use for high efficiency
filters is in pharmaceutical and research laboratories to prevent cross
contamination. Other industries
requiring highly filtered air are semiconductor, LCD manufacturing,
microelectronics, and nanotechnology.
Particles smaller than a single piece of dust can ruin an entire process
in these industries, so clean air is critical.
Industries requiring this level of cleanliness do their manufacturing in
cleanrooms.
·
What is a
cleanroom?
Cleanrooms have a controlled level of
contaminants specified by the number of particles per meter-cubed and by the
maximum particle size. They are
classified by their level of cleanliness.
The following tables are of the different cleanroom classifications:
Cleanroom
Classifications
US FED STD 209E* Cleanroom
standards
|
particle/ftł
|
|
Class
|
0.1 µm
|
0.2 µm
|
0.3 µm
|
0.5 µm
|
1 µm
|
5 µm
|
|
1
|
35
|
7
|
3
|
1
|
|
|
|
10
|
350
|
75
|
30
|
10
|
1
|
|
|
100
|
3500
|
750
|
300
|
100
|
10
|
1
|
|
1,000
|
|
|
|
1,000
|
100
|
10
|
|
10,000
|
|
|
|
10,000
|
1,000
|
100
|
|
100,000
|
|
|
|
100,000
|
10,000
|
1,000
|
*US FED STD 209E was canceled
November 29, 2001.
ISO 14644-1 Cleanroom
standards
|
particle/mł
|
|
Class
|
0.1 µm
|
0.2 µm
|
0.3 µm
|
0.5 µm
|
1 µm
|
5 µm
|
|
ISO 1
|
10
|
2
|
|
|
|
|
|
ISO 2
|
100
|
24
|
10
|
4
|
|
|
|
ISO 3
|
1,000
|
237
|
102
|
35
|
8
|
|
|
ISO 4
|
10,000
|
2,370
|
1,020
|
352
|
83
|
|
|
ISO 5
|
100,000
|
23,700
|
10,200
|
3,520
|
832
|
29
|
|
ISO 6
|
1,000,000
|
237,000
|
102,000
|
35,200
|
8,320
|
293
|
|
ISO 7
|
|
|
|
352,000
|
83,200
|
2,930
|
|
ISO 8
|
|
|
|
3,520,000
|
832,000
|
29,300
|
|
ISO 9
|
|
|
|
35,200,000
|
8,320,000
|
293,000
|
Cleanroom class
comparison
|
ISO 14644-1
|
FED STD 209E
|
|
ISO 3
|
1
|
|
ISO 4
|
10
|
|
ISO 5
|
100
|
|
ISO 6
|
1,000
|
|
ISO 7
|
10,000
|
|
ISO 8
|
100,000
|
Common particles and their sizes
(Sizes are in
microns (μm))
·
Human hair 70 –
100 μm
·
Human sneeze 10 -100
μm
·
Pollen 5 – 100 μm
·
Spores 6 –
100 μm
·
Mold 2
– 20 μm
·
Smoke 0.01
– 1 μm
·
Bacteria 0.35
– 10 μm
·
Anthrax 1x6
μm
Choosing
the right filter
First
you need to ask yourself “what am I trying to filter?” Are you trying to filter dust? Odors?
Sea salt? Chemicals? Next you need to know the filter’s
application. Will it be used for recirculation
units? Cleanrooms? Medical facilities? Tools?
What level efficiency do you require?
Answers
to these questions will vary as will the type of filter you should use. Below are our recommended uses for filters
based on specific applications.
|
APPLICATION
|
PERFORMANCE CLASSIFICATION
|
Cambridge Filter
PRODUCT SERIES
|
|
Air handling /
Ventilation / Recirculation Units / Ducts
|
Particulate / Medium
Efficiency
|
Aero-Answer Series;
Enzymic Filter Series
|
|
|
Chemical / Odor
Removal
|
ChemArrest
|
|
|
HEPA / ULPA
|
Absolute Filter;
Enzymic Filter Series
|
|
Cleanroom Air
Outlets / Cleanroom Equipment
|
Chemical
|
ChemArrest
|
|
|
HEPA / ULPA
|
GIGA Filter Series;
PTFE Filter; Absolute Filter Series; High Temperature Absolute Filter Series;
Enzymic Filter Series
|
|
Exhaust
|
Chemical / Odor
Removal
|
ChemArrest Series
|
|
Medical Facilities
|
Particulate /
Charcoal / HEPA
|
AU Series
|
|
General Air Handling
|
Particulate / Medium
Efficiency
|
CP Filter; Neo-Flo
Series; Neo-Cap Series; AeroFold Series; Hi-Pac Series
|
If
you are still uncertain about what filter you should be using in a particular application,
contact one of our sales representatives.
Filters
are used to clean air in a variety of applications. They work to protect people in public
buildings, patients in hospitals, and critical manufacturing processes. Filters are carefully engineered and designed
to operate at specified efficiencies. It
is important to know why a filter is being used and what requirements need to
be met (for example, efficiency, airflow, pressure drop, and dimensions) to
optimize the filter’s performance.
Cambridge Filter is committed to quality and service. Let us help you with your filtration needs.
