What Your Housekeeping Staff Need to Know about Vacuum Filtration?

The use of efficient vacuum cleaners and filters can significantly improve indoor air quality (IAQ), according to an Environmental Protection Agency (EPA) study.

The one-year study, conducted at the Frank Porter Graham Child Development Center in Chapel Hill, North Carolina, found that efficient vacuum cleaners, along with an organized cleaning program, can greatly reduce the level of dust, bacteria, and fungi found in carpet and
ambient air.

The study is important, EPA Research Analyst Jeff Bishop said, ‘‘because it provides authentic baseline information on how specifically to improve indoor air quality with relatively simple maintenance.’’ Interestingly, the study found that surface and carpet levels of dust and bacteria correlate with airborne levels, showing that dust distributes itself evenly within a facility, and that the proverbial ‘‘white glove test’’ has validity in determining not only cleaning quality but overall IAQ levels. Important among methods of reducing whole building dust levels was the use of high-efficiency vacuum bags or filters.

Filter Factors

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.

Microns Matter

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 buildings are ‘‘tighter’’—with less air exchange to dilute airborne dust—and people are reacting to the respirable particles (mostly ranging between 1 and 10 microns) they are breathing in many energy efficient facilities. Statistics indicate 50 million Americans, one of every five people, suffer from allergen-related diseases. Many allergic reactions are caused by airborne carpetand upholstery fibers, pet dander, molds, spores, dust, dirt, bacteria, and the feces and body parts of dustmites, dispersed by inefficient vacuuming. While many filters remove dust down to one micron, the critical question is, how much one micron dust is captured? Less desirable filter arrangements may capture only 30% of one micron particles, while better filter configurations allow removing 99% or more of those particles. That brings us to the issue of filter 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. Bycontrast, 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 1micron 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 air volume 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 volume 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 noticeable debris and dust, old-style cloth or paper bags were considered adequate. However, with the current emphasis on IAQa nd building 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]—highefficiency filters of several layers—is necessary to effectively remove and retain contaminants smaller than 10 microns. Micro filters greatly increase vacuum efficiency.

One study showed that a standard paper filter bag removed only 39.9 percent of debris 10 microns in size, while a micro filter bag removed over 99% of these particles. Likewise, a standard paper filter bag removed only 16.3% of 1 micron particles, whereas micro filters in two to four-stage configurations removed 95–96% of one micron debris. For this reason, micro filters are now increasingly used in commercial vacuuming applications. Even greater filtration can be achieved with high filtration disc media.

Tests show this filter medium captures 99.79% of .3-micron particles (near HEPA efficiency) at a fraction of the cost of HEPA filters. The medium also removes 99.98% of 2-micron and 99.96% of 1-micron particles. 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 or high filtration discs, 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.

Ensuring Sustained Suction

Old-style. cloth and paper vacuum bags catch pollens, plant spores, and visible dust. Yet, particles quickly clog the pores of these filters, restricting airflow and significantly reducing suction. As a result, vacuuming is less effective. More debris is left in the carpet or on the floor or—agitated by a beater brush—it is broken up and dispersed into the surrounding environment. The use of micro filter technology has alleviated this problem to a large extent. Note the chart showing suction loss using a standard paper filter bag versus a bag composed of micro filter material when vacuuming 20–120 grams of fine road dust.

       Suction Loss

Standard Dust Bag vs. Micro Liner

Grams of Road DustStandardMicro-Linear

Despite the advances in vacuuming technology and filtration, one element of vacuuming is potentially more critical to maintaining good filtration than any other.

The Critical Vacuuming Part (People)

Having selected an appropriate filter combination for your application, the key to maintaining adequate suction and filtration is filter maintenance. Today’s filters—as opposed to the old style. disposable single-layer paper bags—can be cleaned and reused several times, and vacuum technicians should be encouraged to do this on a regular basis, perhaps as often as every 30 minutes to two hours of vacuum time, depending on the soil conditions.

Regular cleaning maintains suction and prolongs the life of the filter and the vacuum cleaner, resulting in more effective vacuuming and ensuring a healthier, more comfortable environment. Regular inspection of filters also allows detecting punctures that allow fine dust to pass through and contaminate the room. Clearly, beyond equipment, ensuring effective vacuuming and filtration means training and educating the people using the tools.