Small hazardous, and even non-hazardous, particles may cause big problems when inhaled. That’s why HEPA and ULPA filters (see sidebar, “Filter Terms and Definitions”) were created - to help stop that from happening.
These filters, in properly sealed vacuum cleaners, work very well at capturing fine particles, but there’s a catch—they only trap particles in air passing through the filter media.
The problem is: many fine particles never make it that far.
The questions are:
1) Where are the offending particles coming from and where are they going?
2) What’s the best way to remove those contaminants from the indoor environment, or prevent them from entering the room and breathing space to begin with?
3) How can vacuum cleaners help or hurt the removal / dust-minimization process, and when are vacuum cleaners, quite frankly, part of the problem?
What’s In the Air?
In non-cleanroom environments where the air is not strictly controlled through extensive engineering and air handling protocols, the indoor air is full of many types of particles. These particles originate from tracked-in dirt, drift in from the outside air, are sloughed off of skin or clothing, are released from other living things (e.g., mold, bacteria or indoor plants) or result from the breakdown of furnishings such as fabric upholstery or carpeting.
Chances are good that the air you are breathing right now contains a fair amount of ultra fine dust below the visible spectrum (basically everything smaller than about 10 microns), and there’s very little your vacuum cleaner can do about those already-floating particles—no matter how good its filters are.
How Do You Remove Those Particles?
Your vacuum cleaner, as a general rule, is really only efficient at trapping particles that have settled onto the floor or whatever surface you’re vacuuming.
Even many room air cleaners are of limited effectiveness in typical building environments, because every time someone walks across a room, opens a door or window, or flips on the central air handling unit, thousands if not millions of superfine particles are introduced into the breathing space as the room air is disturbed or exchanged. Since portable air cleaner airflow rates are often fairly low in relation to the rate of room contamination, many people with portable air cleaners may still end up breathing more dust than they realize.
How can you stop or prevent dust? Well, you can’t, at least not completely, since even humans produce their own organic dust and the surfaces within the building are also constantly “shedding” micro-particles.
Of course, you can make sure you have good entrance matting in place, so outdoor contaminants and dusts are not tracked in as much.
You can also try to cleanup or contain other sources of fine particles (e.g., paper dust from tissue boxes, dirty air ducts or HVAC filters, etc.)
Finally, you can make sure that the processes you use to clean your home, remove rather than redistribute dust as much as possible. This would include vacuuming surfaces with an efficiently filtered vacuum cleaner.
How Can Vacuum Cleaners Help or Hurt?
Generally, any movement across flooring - including the movement of a vacuum cleaner - launches microscopic dust particles into the air.
The impact of a vacuum’s beater brush can be especially problematic, and, in some cases, may make a vacuum’s high-end filter setup somewhat irrelevant.
Also, remember, there is an inverse relationship between great filters and great airflow. The more you slow down the air by filtering it with a dense filter, the less airflow makes it through the filter and the less soil you may be removing from the surface being vacuumed. It’s basic physics.
Thus, in some cases, the vacuum cleaner itself creates more problems than it solves, and, at times, a very high-efficiency filter prevents a vacuum cleaner with inadequate airflow and lift from cleaning well.
Do you need HEPA & ULPA Filters?
If you are directly vacuuming very hazardous materials or operating in a controlled cleanroom environment, it’s necessary to have this level of filtration. In many, perhaps most other environments, it’s just not necessary and sometimes not even helpful.
Consumer Reports, in its testing of many household vacuum cleaners, says you don’t necessarily need HEPA filters (not to mention the more stringent ULPA filters) to have good dust capture—but that it’s more important to consider the vacuum’s overall design, the quality of its micro or other standard filters, and how it all works together. We agree.
A Recent Study Shows: In Some Cases HEPA Doesn’t Help
I read with considerable interest the following item published online and picked up by Reuters:
‘High-efficiency’ vacuums no protection against dust mites
A team at the North West Lung Centre, run by the [UK] University [of Manchester] and based at Wythenshawe Hospital, has discovered that vacuum cleaners with ‘high-efficiency particulate air’ or HEPA filters are no more effective than standard models at reducing exposure to dust mites.
The team compared nasal air samples taken before and during vacuum cleaning using both HEPA and non-HEPA vacuum cleaners. They found a small increase in exposure to dust mites during vacuuming with either type of machine, which was increased when emptying the dust compartments of either.
Lead investigator Dr Robin Gore said: “These vacuum cleaners are marketed to allergy sufferers on the basis that they reduce a person’s exposure to airborne particles raised from carpeted floors. For allergy sufferers, such particles can trigger asthma attacks. However, we have already found that both HEPA- and non-HEPA vacuum cleaners can actually increase an individual’s exposure to particles containing cat allergens.
“These latest findings further suggest that there is no significant advantage to using a HEPA vacuum cleaner to reduce exposure to airborne particles like dust mites.
“In combination with our previous work, the study seems to confirm that high-efficiency vacuum cleaners confer no benefits and should not currently be specifically recommended to allergy sufferers as a means of reducing personal exposure to allergens, either by their manufacturers or health professionals.”
Professors Ashley Woodcock and Adnan Custovic were co-investigators in the study, which was published in the January 2006 issue of the European Journal of Allergy and Clinical Immunology.
The University of Manchester (http://www.manchester.ac.uk/) is the largest higher education institution in the UK, with 24 academic schools and over 36 000 students in 2005/6. Its Faculty of Medical & Human Sciences (http://www.mhs.manchester.ac.uk/) is one of the largest faculties of clinical and health sciences in Europe, and the School of Medicine (http://www.medicine.manchester.ac.uk/) is the largest of the its five Schools. It encompasses five teaching hospitals, and is closely linked to general hospitals and community practices across the North West of England.
Interesting, isn’t it?
The study is a bit misleading though since it implies that high-efficiency or HEPA filters do not control allergens. They do: when the air containing those particles passes through the filter media.
However, there’s another consideration: dust mites and their feces, microscopically speaking, are bowling balls and HEPA is overkill. Cat allergen is another matter.
According to Dr. Thad Godish, professor of Natural Resources and Environmental Management at Ball State University, Muncie, Indiana:
“Mite fecal pellets [feces] are large (10 to 35 microns). As a consequence, disturbance of floor and other surface dusts is necessary to disperse them in air. Because of their large size and mass, they settle out rapidly and do not form true aerosols in the fashion of cat dander and mold spores. Consequently, exposure is episodic and is typically associated with bed disturbances during sleep, bed-making, and house-cleaning activities. Only the smallest of particles in the fecal pellet range have the potential to enter and deposit in the upper respiratory system.”
The real problem is that "sweepers" (vacuums with beater brushes or bars) can stir allergens of all types into the air if airflow and lift are not sufficient at the tool orifice.
HEPA sweepers or uprights can make matters worse in some cases because of back pressure by the denser HEPA media.
Cat dander is a real problem (it's superfine) and many vacuums just stir much of it up.
For example, a study conducted at the University of Virginia Health Sciences Center* determined that, “Vacuum cleaners are essential for the removal of dust from the surface of carpets; however, they may also contribute to airborne dust both by leakage through the cleaner and disturbance of floor dust … In houses with cats, different models of vacuum cleaners could either reduce or increase total airborne allergen …These results suggest that cat allergen is a good model for studying the effectiveness of vacuum cleaners recommended to allergic patients.”
To summarize, it doesn't do any good for a vacuum to have great filters when it isn't picking soils up.
It’s unwise to think that super filters will solve IAQ problems that originate elsewhere.
The views expressed in this article are those of the author and do not necessarily reflect the position or perspective of Housekeeping Channel LLC.
Journal of Allergy and Clinical Immunology 1993 Apr;91(4):829-37.
The effect of vacuum cleaners on the concentration and particle size distribution of airborne cat allergen.
Woodfolk JA, Luczynska CM, de Blay F, Chapman MD, Platts-Mills TA.
Department of Medicine, University of Virginia Health Sciences Center, Charlottesville 22908.