NASA’s 18 Air-Purifying Houseplants: Do Plants Really Clean Indoor Air?

A leafy plant can make a desk or living room feel more inviting. It can also give you the small pleasure of noticing a new leaf unfurl. Those are good reasons to enjoy houseplants without asking them to perform an air-cleaning job they cannot realistically deliver.

The popular claim that a few indoor plants will substantially purify a home’s air grew partly from controlled experiments. The missing step is whether those results translate to an ordinary occupied room.

The 2015 version of this article put the popular case well: houseplants do wonders for a house, it said, breathing new life into a room, adding a bright pop of colour and purifying the air; not all plants are equally effective at filtering harmful airborne toxins and pollutants; NASA conducted a Clean Air Study to identify the best air-filtering indoor plants, all commonly found at local flower shops; and Love The Garden turned it into an infographic of 18 NASA-recommended plants and the common toxins each one can treat. The first two claims are true; the purifying part is where the evidence below matters.

Variegated pothos houseplant growing in a terracotta pot — Epipremnum aureum “Marble Queen” grown as a houseplant. Photograph: Spnq, CC BY-SA 4.0. Decorative plant photograph, not evidence of room-scale air purification. Source. Image license. Resized and compressed; image content unchanged.

What the NASA work actually explored

A 1989 NASA-associated study of indoor plants investigated pollutant removal in controlled chambers. Led by B. C. Wolverton with the Associated Landscape Contractors of America, it tested how plants removed benzene, formaldehyde and trichloroethylene. Most studies of this kind used small sealed chambers, often one cubic metre or less. Such experiments can reveal biological processes, but a chamber gives researchers control over factors that change continually in buildings.

A real room has incoming and outgoing air, changing pollutant sources and a different relationship between plant size and air volume. Showing removal under experimental conditions does not by itself establish a useful room-scale effect.

Later research put the numbers in context

A review by Bryan Cummings and Michael Waring, published online in 2019, examined 12 studies and 196 experimental results. It translated plant-related removal into clean air delivery rates, a metric that allows comparison with other air-cleaning processes.

The authors concluded that ordinary numbers of potted plants provide too little removal of volatile organic compounds to compete with typical building air exchange. Their calculations required implausibly dense plant coverage to produce a comparable effect: roughly 10 to 1,000 plants per square metre of floor space to match a building’s air-handling system, or even a couple of open windows.

This finding concerns passive potted plants. It should not be stretched into a verdict on every engineered system that combines plants, growing media and actively circulated air.

What actually belongs in an indoor-air plan

The U.S. Environmental Protection Agency’s guidance centres on controlling pollution sources, improving ventilation when appropriate and using suitable air cleaning or filtration.

Start by identifying the problem rather than buying an object labelled “purifying.” Cooking particles, a persistent emission source and polluted outdoor air do not create the same practical situation. Ventilation and filters also need to suit the conditions and pollutant involved.

A plant label should not be treated as evidence that a room’s air is safe or that a source of contamination has been dealt with.

Give houseplants a role they can comfortably fill

Choose a plant that fits the available light, space and care you can provide. Enjoy its form and growth, keep the container draining properly and follow reliable care information for the species.

If the plant has lost its label, our guide to checking a Pl@ntNet identification can help you begin investigating what it is.

There is no need to retire your favourite fern or pothos after reading the research. Let it be a plant: an interesting living presence, with new growth to watch and no impossible promise attached.