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Questions and answers on the electrostatic filter
1) What is
dust?
Atmospheric dust usually contains soot and smoke, silica, clay, decayed
animal, insecticide dust and vegetable matter, organic materials in the
form of lint and plant fibers.
2) What does
electrostatic really mean?
Breath electrostatically charged media contains both positive-charge and
negative-charge fibers. The particulates in the air passing through the
filter will be either positively or negatively charged. Therefore, the
charged particles will then stick to the filter
3) Does the
filter remove odours?
No, but in the case of tobacco and wood smoke, removing the smoke can
help reduce the odour
4) Is the
electrostatic filter anti-microbial?
The filtering material will not support the growth of bacteria, mould,
mildew or fungi in normal use. No unnecessary chemicals have been added
to the filter.
5) How often do
I need to change electrostatic filter?
The recommended change interval is 3 months. However, the effectiveness
and life of the filter can vary and will depend on the individual
conditions in your room. Unusually dirty duct work, construction work,
furniture or drywall sanding, pets, the presence of smokers and running
the fan continuously are some of the things that can shorten the life of
your filter. In these cases, change the filter more frequently
6) Do I have to
worry about restricted airflow with the electrostatic filter?
The electrostatic filter is designed to operate in most industrial
furnaces. If a electrostatic filter remains in use longer than 3 to 4
months, it may begin to restrict airflow or cause the Breath system to
foul or even malfunction.
7) Will the
electrostatic filter eliminate the need for cleaning?
No, electrostatic filters will reduce the need for cleaning but it won't
eliminate it. Atmospheric dust consists of a wide variety of particulate
ranging in size from .001 micron to a relatively large 100 microns.
Because of the density of the large particles, they will settle out on
your furniture long before they reach your filter
8) What makes
the electrostatic filter so different?
The media in our filter is a blend of blown micro fibers (BMF) and
patented fibers (a patented fiber type, which gives our media a
permanent electrostatic charge). Many competitive filters are blends of
cotton and polyester without the electrostatic features.
9) What does an
electrostatic filter do?
Electro statically charged fibers act like tiny magnets to attract and
capture particles that can pass right through Fiberglas filters.
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Figure
1: Filter differences
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10)
How does a filter clean the air in my room?
The air in our rooms contains millions of tiny particles. A filter
removes particles from the air when a particle collides with the
filter media and sticks. The more times air passes through the
filter, the more opportunity the filter has to capture particles.
In time, the air contains fewer and fewer particles, thus becoming
cleaner and cleaner.
11) What
is a HEPA filter, this competing technology that my customer is
currently using?
HEPA stands for High Efficiency Particulate Arrestance filter.
These filters historically have been used in clean rooms and
nuclear applications, and some are beginning to show up in
tabletop room air cleaners. The HEPA filter is a dry media filter
that captures 99.97% of particles sized 0.3 microns and larger.
HEPA filters are typically not found in whole house furnaces.
12) What
should I consider when advising a Breath air treatment filter to
my client?
Filter efficiency - the type, size and number of particles
the filter is able to trap. See table 1 below were the
electrostatic filter (pleated, permanently charged electrostatic)
is compared to different filters
Performance - overall filter performance depends on a
number of factors:
Is it pleated? A pleated filter provides additional surface
area on which particles can be trapped.
Is it electro statically charged? Filters with electrostatic
charging can attract and capture particles that other filters can
miss.
What type of particulates does it capture?
What is the filter's efficiency?
13) How
big are certain particles and what is the differences between
normal filters and electrostatic filters?
Table 1
and table 2 listed below should speak for itself.
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Table
1: Particles sizes
14) What
is a micron?
One
micron equals one millionth of a meter. 10.000 microns equal one
cm. To give you an idea how small that is, consider that a human
hair is about 70 microns in diameter
Table
2: Filters efficiency
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Breath,
ultraviolet disinfection treatment
D)
Benefits of using UV disinfection technology.
Although
seemingly new to the average end user, the use of UV light as
means of disinfection has been a proven process for many years.
The UV method of disinfection is now widely recognised by federal
and state regulatory agencies. In addition, as the concern of
chemical contamination increases, many companies have accepted UV
as a viable disinfection treatment option for air or water
treatment.
Used by
leading companies around the world, UV disinfection is trusted to
provide microbiologically pure mediums such as air without the
unwanted effects of alternative treatment. Similarly, health
authorities are becoming increasingly aware of the benefits of UV
disinfection without the use of chemicals.
How does
Ultraviolet work?
Strong sunlight disinfects air by permanently de-activating
bacteria, spores, moulds and viruses. Over a century ago,
scientists identified the part of the electromagnetic spectrum
responsible for this well-known effect; wavelengths between 200nm
and 315nm, often called UV-C. The most effective single wavelength
is typically UV at 253.7nm, however recent research has shown that
271nm light and 263nm light are the most effective UV wavelengths
for the deactivation of particular target organisms.
The
mechanism of kill is well documented and unlike chemical
disinfectants the organism is unable to develop any immune
mechanisms. The mechanism of kill involves the absorption of
photons of UV energy by the DNA, which fuses the DNA and prevents
replication. DNA (Deoxyribonucleic acid) consists of a linear
chain of nitrogen bases known as purines (adenine and guanine) and
pyrimidines (thymine and cytosine). These compounds are linked
along the chain by sugar-phosphate components. The DNA of most
forms of life is double stranded and complimentary; the adenine in
one strand is always opposite thymine in the other, and linked by
a hydrogen bond, and guanine is always paired with cytosine by a
hydrogen bond. The purine and pyrimidine combinations are called
base pairs. When UV light of a germicidal wavelength is absorbed
by the pyrimidine bases (usually thymine) the hydrogen bond is
ruptured. The dimer that is formed links the two bases together,
and this disruption in the DNA chain means that when the cell
undergoes mitosis (cell division) the DNA is not able to
replicate. The most effective wavelength to achieve this effect is
at 253.7nm
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Figure
2: DNA inactivation by UV light |
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How is UV light
generated?
Ultraviolet
light is most typically generated from a low pressure UV lamp. Low
pressure UV lamps are the most common lamp type and are the oldest and
most reliable source of ultraviolet light. They consist of a quartz
envelope that separates two tungsten filaments. The lamp is evacuated to
<10torr and approximately 60mg of mercury is introduced into the
quartz envelope. The spectral output of this lamp type is monochromatic,
a single line output at 253.7nm. A fluorescent lamp is a low-pressure
lamp that has the inner surface of the lamp coated with phosphors to
absorb all of the 253.7nm light, and only emit the longer wave visible
light. This lamp has an output that is temperature dependent and can
take up to 60 seconds to get to full output in cool or hot air.
The optimal
operating temperature is 15oC, and the lamp output will fall
off slightly as the lamp temperature migrates from this condition.
Frequent switching of these lamps will have a detrimental effect on lamp
life, and the most probable failure mode will be failure of the
filaments, which become brittle. For each lamp on-off switching one
running hour has to be deducted from the effective hours. Typically
these lamps have an efficiency of 25-30% on UV efficiency, which is
temperature dependent. The lamp life is typically 8000 hours, and the
lamps have the advantage of being mass produced and easily second
sourced.
Disinfection
means the deactivation of microorganisms. This is achieved by UV light
with wavelengths between 200 and 315 nanometers. The choice of applying
UV technology for air treatment depends mainly on:
-
amount of air to be treated (flow)
-
transmission (quality) of the air (penetration factor of UV
light)
-
amount of UV energy to obtain the required deactivation of
specified micro-organisms (dose in mJ/cmē)
-
temperature of the air
-
UV light
provides the most efficient, economic, safe and reliable method of
disinfection currently available. Moreover, this quick and
environmentally friendly method has been used worldwide for several
decades.
However,
despite its obvious advantages, traditional UV technology has certain
limitations:
- A) UV
tubes fouled by air particles have reduced output resulting in
lesser performance.
- B) UV
tubes age and need to be replaced after a certain amount of
running hours.
Effect of
particles on UV disinfection
Shading limits
the exposure of individual and particle associated bacteria to UV light
Scattering and
absorption of UV radiation limits the exposure of particle-associated
bacteria to UV light
Incomplete
penetration of UV light limits the exposure of bacteria embedded in
large particles.
In a
well-designed UV disinfection air chamber, particle shading has not been
a problem. The scattering of UV light has not been considered to be a
significant factor, as the scattered light can still inactivate other
individual and particle-associated bacteria. However because of
increased travel distance between the light source and the targeted
organism, scattering does decrease the average UV intensity within the
chamber. In addition, some UV energy is lost at the point of scattering.
The absorption of UV light by materials can be a significant factor.
Clearly, if very large particles are present, the UV tubes will not
inactivate embedded microorganisms. In other words without a
(electrostatic) filter in front of the UV tubes the effect of these UV
tubes would be reduced dramatically resulting in a poor disinfection.
The performance
of the UV tubes
In the breath
air treatment unit two 15-watt UV tubes are placed behind the
electrostatic filter. Possible particles will be caught by this high
efficiency filter, which ensures that fouling is kept to an absolute
minimum.
·
The chamber volume in the Breath module combined with the
speed of the ventilator ensures a minimum staying time
(seconds)
·
The lamp strength and positioning combined with the high
purity air ensures a minimum intensity, which all
microorganisms will receive.
The outcome of
this staying time times the intensity guarantees a dose of 10-12mj/cm2
at the end of lamp life. (The formula commonly applied for UV dose
calculation is: retention time (seconds) * intensity (mW/cm2)
= dose (mJ/cm2)
A dose of 10
-12mj/cm2 guaranteed in a re-circulation system guarantees a
log reduction on average count on microorganisms of 90 - 99% also
referred to as a log 1 to log 2 reduction per pass. With a
re-circulation speed of 4 times per hour higher reductions will be
achieved.
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E)
Conclusion.
The Breath air
treatment module guarantees a full and reliable treatment of air(*)
Treatment
includes high reductions on particles, organics and microorganisms.
1) A coarse
filter, which protects the electrostatic filter from rapid fouling,
eliminates large particles.
2) An
electrostatic filter, which protects the UV tubes from fouling,
takes out more than 58% of all particles and organics up to a size
of 0.3 micron.
3) UV tubes
eliminate 90 to 99% of all microorganisms passing through.
Knowing that
the air is treated continuously and up to 4 times per hour the air
purification will even improve per every pass.
The breath
offers two solutions within one unique concept:
· A
high performance electrostatic filter eliminating smoke,
pollen, fungi, yeast and other organics.
· A
highly effective disinfection unit guaranteeing 90 to 99%
reduction in a single pass.
Because of this
the Breath can be used in environment were smoke, pollen or simply a
high concentration of particles needs to be reduced. Applications are
offices, homes, canteens, restaurants, bars, hotel rooms etc.
Alternatively
the Breath can be offered in rooms were microbial control is needed such
as laboratories, clean rooms, hospitals, waiting rooms or practices from
doctors and dentists etc.
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