WellisAir Is Not a HEPA Replacement — and That’s the Point

What a HEPA filter is for

A HEPA filter is very good at what it does. It captures 99.97% of particles at 0.3 micrometers — the hardest size to catch, which is why the standard uses it — to a definition set by the U.S. Department of Energy. If your problem is dust, pollen or dander, that is the right purchase, and WellisAir will not do that job.

What WellisAir does is the other half. The half a filter was never built for, and the half almost nothing in a typical home addresses.

Half the problem has a product. The other half mostly does not.

The EPA puts the division plainly: “most filters are designed to filter either particles or gases” — and the CADR rating that comes with a purifier is, in its words, “for particles only.” That is not a criticism of filters. It is the regulator describing what a filter is (EPA, Guide to Air Cleaners in the Home).

So a home with a good HEPA unit has solved the particle half. The question is whether the gas half matters enough to solve too.

It matters more than most people assume

Researchers at Lawrence Berkeley National Laboratory screened 267 indoor air pollutants and modeled the chronic health burden of the 70 with enough data behind them, in disability-adjusted life years.

Three pollutants accounted for the vast majority of it: PM2.5, acrolein and formaldehyde. Two of those three are gases. Acrolein alone drove about 16% of the modeled burden and formaldehyde about 4% — roughly a fifth of the total, from two compounds no filter captures.

For scale, the same analysis put the total indoor burden on par with or greater than secondhand tobacco smoke and radon: 1,100 disability-adjusted life years per 100,000 people a year, against 51 for secondhand smoke and 13 to 79 for radon.

Those are hazards people act on. They test for radon and they stopped smoking indoors. The gas half of indoor air carries a comparable burden, and in most homes nothing is working on it at all.

Logue, J. M., Price, P. N., Sherman, M. H. & Singer, B. C. (2012). A method to estimate the chronic health impact of air pollutants in U.S. residences. Environmental Health Perspectives, 120(2), 216–222.

Why almost nobody addresses it

Gases need either activated carbon or chemistry. Carbon works — the EPA says so, “provided that there is a large amount of material used in the filter.” The quantity is the catch. A 2022 study in Chemosphere estimated that a filter needs 7 to 13 ounces of carbon to last 30 days in clean indoor air, up to about 2½ pounds in a typical home, and 7 to 33 pounds or more during a wildfire (Maximoff et al., 2022; three of its four authors were employed by Molekule, which sells a competing non-carbon technology).

For scale, seven pounds of carbon on its own weighs nearly twice an entire WellisAir unit, which is 3.7 pounds including its cartridge. A carbon bed that size is not something a portable purifier is built to carry — and most manufacturers do not publish the weight of carbon in their units at all, which is why asking for it is one of the more useful questions you can put to one.

What WellisAir does about it

  • Toluene, ammonia, formaldehyde

    99.5% of toluene in 2 hours. 80% of ammonia and 65% of formaldehyde in 4 hours.

    Korea Conformity Laboratories, report 026961. Toluene comes off paint, adhesives and solvents; formaldehyde off pressed wood and new furnishings; ammonia off cleaning products.

    Reports and citations 

  • Acetic acid

    72% in 2 hours, measured at 30, 60, 90 and 120 minutes.

    Korea Conformity Laboratories, report CT23-092814E.

  • Total VOCs, against a control

    94.3% of total VOCs and 93.4% of formaldehyde at 30 minutes, measured against a room running at the same time with no device in it.

    CRESCA, Polytechnic University of Catalonia, report 20190930. Formaldehyde is one of the three pollutants the Berkeley analysis ranked highest.

  • And it reaches the surfaces too

    Hydroxyls travel with the air rather than waiting for it to be drawn through an intake. In CRESCA’s oxidation test, potassium iodide strips placed 12 meters from the unit oxidized after eight hours of running, while the control strip did not.

Both, not either

Most homes have both problems. A filter solves one of them well. The other one is usually running unaddressed — and on the Berkeley numbers it is not the smaller of the two concerns.

If you already own a HEPA unit, keep it. WellisAir is what goes next to it.

Shop the unit — $549.99What to look for when buying

HEPA and hydroxyl questions, answered

Is WellisAir a replacement for a HEPA filter?

No, and it is not sold as one. A HEPA filter captures particles — dust, pollen, dander, smoke particulate — and WellisAir does not do that. It has no filter and no CADR rating, because CADR measures how fast a device clears particles from a chamber and a hydroxyl radical does not capture particles.

What it does is the gas side: VOCs, off-gassing, cooking and pet odors, musty smells. Those are different molecules needing a different mechanism, which is why the EPA says most filters are built for one or the other.

Can I run both?

Yes, and plenty of customers do. They are not competing for the same job — one is pulling particles out of the air passing through it, the other is breaking down gas-phase compounds in the room and on its surfaces. Running both is the complete answer to indoor air; running one is half of it.

Which should I buy first?

Whichever matches the problem you actually have. If someone in the home reacts to pollen, dust or dander, buy the filter first — that is a particle problem and a filter is the correct tool.

If what bothers you is smells, off-gassing from new furnishings, cooking odors, smoke that gets indoors or a musty room, that is the gas half, and a filter will not resolve it however good it is.

Does a HEPA filter remove VOCs or odors?

Not meaningfully on its own. A HEPA filter is a particle filter; gas molecules pass straight through the fibers. Some units add a carbon layer for gases, which does work — the EPA says so “provided that there is a large amount of material used in the filter.”

The published estimates put that amount at 7 to 13 ounces of carbon for 30 days in clean air and up to 33 pounds or more during a wildfire, which is well beyond what a thin carbon-coated mesh holds.

What does WellisAir do that a filter cannot?

Two things. It works on gases rather than particles — breaking the molecules apart instead of trying to trap them — and it works away from the unit, because hydroxyls travel with the air rather than waiting for air to be drawn through an intake. CRESCA measured oxidizing activity on test strips 12 meters from the device after eight hours.