Q: How does a HEPA filter work on a vacuum, and what should I look for to make the best purchase?

 

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A: A vacuum cleaner draws air in through the cleaning tool. That air carries dust with it. Most vacuum cleaners have a bag that allows the air to pass through the paper walls of the bag but traps the dust, just the way a coffee filter keeps the grounds but lets the water through.

Unfortunately, some of the dust particles, particularly those carrying allergens, can pass through the microscopic pores in the paper bag. After the air carrying allergen particles passes through the bag, it passes through the blower and is emitted into the room.

A HEPA vacuum has another highly efficient filter after the blower. This filter allows the air from the blower to pass through but traps the microscopic allergen particles that escaped the bag.

The most important features in a HEPA vacuum are the HEPA filter itself and how it is held in place. The filter itself should be made of a pleated, semi-rigid material held in a frame. The frame must be held tightly in place by an airtight gasket. The gasket prevents allergy-laden air from bypassing the filter.

Some vacuum cleaners have flimsy, pleated paper filters that look like the material in legitimate HEPA filters; other vacuums have efficient filters in a rigid frame but the filter frame is not held tightly in place, so allergens pass around the filter instead of through it, and escape from the vacuum cleaner. A foam filter is not a HEPA filter.

 

About Jeffrey C. May

Jeffrey C. May is a building consultant, Certified Indoor Air Quality Professional (CIAQP), and author of My House is Killing Me! The Home Guide for Families with Allergies and Asthma(2001) and My Office is Killing Me! The Sick Building Survival Guide (2006), as well as co-author of The Mold Survival Guide: For Your Home and for Your Health (2004), and Healthy Home Tips: A Workbook for Detecting, Diagnosing, and Eliminating Pesky Pests, Stinky Stenches, Musty Mold, and Other Aggravating Home Problems (2008), all published by Johns Hopkins University Press. A former educator and organic chemist (M.A. Harvard University), Jeff is principal scientist of May Indoor Air Investigations LLC in Cambridge, Massachusetts.