We mentioned that standard vacuum cleaners use the bag as a filter medium. If you've ever noticed dust on your vacuum cleaner after using it, you've seen proof positive that this arrangement releases dust (mites and mold) back into the air after liberating them from the carpet. If someone in your household has allergies or asthma, vacuuming with a conventional vacuum cleaner has the potential to cause health problems. Enter onboard vacuum cleaner filtration. Although HEPA filtration is probably the best known filtering method for vacuums, it isn't the only method. Some vacuums use water as a filtering medium, for instance. Others use the principle of electrostatic precipitation. There are even new technologies that make use of UV light to kill microbes and control odor.
Let's take a closer look at HEPA filtration: HEPA is an acronym that stands for high-efficiency particulate air. A HEPA filter is designed to trap a minimum of 99.97 percent of particulates 0.3 microns or larger. That's the optimum or "A" standard, but HEPA filtration in vacuum cleaners may or may not filter that efficiently. Some vacuum filters claim they use HEPA filtration or comparable, but may just have filters that look similar. In some vacuum cleaner models, small amounts of particulate laden air can bypass the onboard filter completely. If you consider air filtration a critical feature in a vacuum cleaner, check out a number of independent testing lab reviews before you buy. A good filter isn't something you can detect from a quick demo on the showroom floor, so defer to the experts.