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Few cleaning processes are as important to IAQ as vacuuming,
and few internal steps are as important to the process as vacuum
filtration. Without proper
filters to catch dust, fine particulate is blown through the
filter media and into the ambient environment. A vital factor to
assess in choosing a vacuum filter is both the size of dust
particles-measured in microns--and the quantity of dust particles
removed from the vacuum's airflow.
A micron is one millionth of a meter, 1/70th the
thickness of a human hair. Single dust particles smaller than 10
microns are so tiny they are virtually invisible. When the main
interest was in removing visible dirt, traditional cloth or paper bags
filtering down to 10 microns were widely used. Vacuums that could
effectively remove particles smaller than that were considered
specialty items-valued only for stringent applications like computer
data centers. Now homes and buildings are "tighter"-with less air
exchange to dilute airborne dust-and people are reacting to the
respirable particles (mostly ranging between .3 -10 microns) they are
breathing in energy efficient dwellings.
Statistics indicate 50 million Americans suffer from
allergen-related diseases. Many allergic reactions are caused by
airborne carpet and upholstery fibers, pet dander, molds, spores,
bacteria, and dust mite feces, dispersed by inefficient vacuuming.
While newer filters remove fine dust, the critical question is, how
much fine dust is captured? Less desirable filter arrangements may
capture only 30% of one micron particles, while better filter
configurations enable removing 99% or more of those particles. That
brings us to the issue of filter efficiency.
EFFICIENCY
"Filter efficiency"--expressed as a percentage-denotes how much
dust of a particular size a filter captures. For example, a filter
that is 95% efficient at one micron, catches 95% of all particles that
size. By contrast, an advertised "1 micron filter" (capable of
removing particles as small as 1 micron) may be retaining only 30
percent of all 1 micron particles, while the remaining 70 percent pass
through the filter and escape. That filter would have a 30 percent
efficiency rating at one micron. Conversely, if the filter arrangement
removed 99 percent of all 1 micron particles, it would have an
efficiency rating of 99 percent. Typically, old-style cloth bags have
an efficiency rating of only about 30 percent at one micron.
AIRFLOW ISSUES
Airflow and lift create suction, traits relating closely to
effective filtration, since dust must be adequately pulled into the
filter's mesh without being pulled through the media by too much
pressure. An integral part of the vacuum's operating system, filters
are only effective when they are carefully proportioned to the airflow
and lift created by the vacuum motor's fan. The filter media is also
critical since material that catches fine dust must "breathe"--letting
air pass through-to create sustained suction and cleaning ability. As
you can imagine, developing materials that trap the finest dust while
sustaining airflow is the goal of vacuuming engineers. Fortunately,
there are several successful filter options that meet this need,
depending on the intended application.
THE RIGHT FILTERS
In the past, when the main concern was the removal and capture
of "large" visible debris and dust, old-style cloth or paper bags were
considered adequate. However, with the current emphasis on IAQ and
wellness, a higher degree of filtration, usually in the form of
layered micro filter media (this media is now used by a number of
manufacturers of vacuum cleaners)-high-efficiency filters of several
layers-is necessary to effectively remove and retain contaminants down
to 1 micron and smaller. Micro filters greatly increase vacuum
efficiency.
One study showed that a micro filter in a four-stage
configuration removed 95% of one micron debris. Newer micro filters
are even more efficient.
More sensitive vacuuming applications require high-efficiency
particulate air (HEPA) or ultra-low penetration air (ULPA)
filters.
More costly than standard or micro filter bags, both HEPA and
ULPA filters are designed to remove more than 99 percent of superfine
particles. HEPA filters remove 99.97 percent of particles .3 micron
and larger in size. ULPA filters are even more efficient, removing
99.999 percent of .12 micron and larger particles. Both-typically
installed as secondary filters "behind" primary filters that catch
larger "gross" dust--rely on numerous brain-like folds or corrugations
of filter media creating tremendous surface area in a relatively small
package to trap fine contaminants without substantially restricting
airflow.
Watch out for ads for HEPA filtration, however, since many
manufacturers' claims are nothing more than marketing hype. True HEPA
filtration requires balancing sufficient filter media with vacuum
airflow, along with a proper seal so that dust isn't leaking from
other places in the vacuum. |
