Start With the Vacuum, Not the Air Purifier

Dust does not hang in the air for long. It settles onto floors, rugs, furniture and shelves, and gets kicked back up each time someone crosses the room. A purifier cleans only the air that passes through it. A good vacuum removes the dust before it is stirred up.

The catch is that an ordinary vacuum can make the air worse. It lifts the visible dirt, but the finest particles, which travel deepest into the lungs, slip through its filter and out the exhaust. Holding a laser particle counter at the exhaust, the inspector found ordinary machines putting out tens of thousands of particles per cubic foot of air, and some far more, while a well-sealed HEPA vacuum read close to zero.

Evidence: Inspector's practice (precautionary).

• A canister rather than an upright. Canisters are more often sealed, though a few sealed uprights exist.
• A bag rather than a dust cup. Emptying a cup puts you in the middle of the cloud. If you already own a bagless machine, empty it outdoors, standing upwind, wearing an N95 or P100 mask.
• A true HEPA filter inside a body that does not leak. Both parts matter.
• No electric power nozzle or beater bar in a sensitive home. The nozzle's own motor vents are unfiltered and throw dust into the room even on an excellent vacuum. An air-driven turbo nozzle handles low-pile carpet; shag and high-pile carpet need a power nozzle, one more reason to avoid them.
• No water-filter vacuums unless they also carry a HEPA filter. The murky water looks convincing, but the tiniest particles pass right through. A 1990 study in the American Review of Respiratory Disease found that a water-filter vacuum raised the level of cat allergen in the air, while a HEPA vacuum kept it contained.

Evidence: Mixed or limited evidence.

Current guidance: Allergy specialists, including the American Academy of Allergy, Asthma and Immunology, advise people with dust or pet allergies to vacuum with a HEPA-filtered machine.

Move slowly and gently, stirring the air as little as possible, so settled dust goes into the machine instead of into the room. Vacuum floors, upholstered furniture and the bed at least weekly, more often with furry pets. Wipe hard surfaces with a damp or microfiber cloth instead of a feather duster or broom. If you are stuck with an ordinary vacuum for now, wear a dust mask, run it just before you leave home for several hours, and keep children out of the room while you work.

A cleaning company's vacuum travels from house to house, carrying other people's dust. In one case, a woman on the highest level of asthma medication, living in a two-year-old house, was sure she had mold. A full inspection found none. Her cleaners had been using a non-HEPA vacuum that had just come from a home with dogs, and she was badly allergic to dogs. She bought a sealed HEPA vacuum of her own and required the cleaners to use it and nothing else. Within a week or two, by the inspector's account, she no longer needed her asthma medicine.

In another case, a woman with a stubborn cough blamed mold. The inspector found a little in the crawlspace, not enough to explain it, but the household vacuum tested badly. After she switched to a sealed HEPA model, she reported her cough about 80 to 90 percent better.

Evidence: Inspector's practice (precautionary). These are single cases, and any change to medication is a decision for your doctor.

A third case shows why the order matters. A girl's bedroom had a purifier humming day and night for two years, yet on inspection day its particle count matched every other room. Carpet and a dust-recycling vacuum were the real problem.

Ask any cleaning service what vacuum it uses. If it is not a sealed HEPA machine, supply your own.

This page is for education only. It is not medical, legal or engineering advice. The inspector whose work this builds on was an environmental consultant, not a physician. Talk with your doctor about health concerns, and use licensed professionals for electrical work and large mold jobs. Products, prices and labs mentioned reflect the years they were recorded and may have changed.

Source: the field work of environmental inspector May Dooley, MS, MA, CMC

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