Air-Purifying Plants: Myth vs. Evidence
What the research actually says about plants cleaning indoor air.
Houseplants do not meaningfully purify the air in a real home or office. The widely shared list of air-purifying plants comes from a 1989 NASA study that measured plants in small sealed chambers, and a 2019 review in the Journal of Exposure Science and Environmental Epidemiology concluded that normal air exchange in a building removes pollutants far faster than any practical number of potted plants. To improve indoor air, ventilate, reduce pollution sources and use an air purifier; keep plants because they make a room nicer.
- Plants that appear on popular 'air-purifying' lists, including the NASA study species
- Good, durable houseplants in their own right
Anthurium
Anthurium andraeanum hybrids- Bright indirect, 3–5 ft from an east or west window; no hot direct sun
- When the top 1–2 in. are dry; about every 7–10 days; less in winter
- ASPCA: toxic to dogs, cats and horses (insoluble calcium oxalates)
Areca palm
Dypsis lutescens (syn. Chrysalidocarpus lutescens)- Bright indirect: 2–5 ft from an east or west window, 4–8 ft back from a south window; brief morning sun is fine
- When the top 1 in is dry: about every 5–7 days in summer, 10–14 in winter; soft water
- Non-toxic to dogs and cats (ASPCA)
Boston fern
Nephrolepis exaltata 'Bostoniensis'- Medium-bright indirect; east window or filtered south/west light
- Keep evenly moist; water when the surface just begins to dry
- Non-toxic to cats and dogs (ASPCA)
Dracaena
Dracaena (D. marginata, D. fragrans, D. reflexa, D. deremensis)- Bright indirect; 3–6 ft from a south window or near an east/west one; green types tolerate medium light, variegated need more
- When the top 1.5–2 in are dry: every 5–7 days in summer, 12–18 days in winter; rain, distilled or RO water
- Toxic to cats and dogs: saponins (ASPCA)
Peace Lily
Spathiphyllum spp.- Bright indirect light for blooms; tolerates low light (no direct midday sun)
- When the top 1 inch is dry or leaves begin to sag; every 5–7 days in summer, 10–14 in winter
- Toxic to dogs and cats per ASPCA (insoluble calcium oxalates)
Philodendron
Philodendron spp. (heartleaf P. hederaceum and others)- Bright indirect; heartleaf tolerates low light
- When the top 1-2 inches are dry; about every 7-10 days in summer
- Toxic to cats, dogs and horses (ASPCA)
Snake plant
Dracaena trifasciata (syn. Sansevieria trifasciata)- Low to bright indirect; tolerates some direct sun
- When soil is fully dry: every 2–3 weeks summer, 4–8 weeks winter
- Toxic to cats and dogs (ASPCA): saponins
Spider plant
Chlorophytum comosum- Bright indirect; tolerates medium light
- When top 1 inch is dry: ~weekly summer, every 10–14 days winter
- Non-toxic to cats and dogs (ASPCA)
Comparison: which one fits your conditions
| Plant | Light | Water | Difficulty | Pets |
|---|---|---|---|---|
| Anthurium | Bright indirect, 3–5 ft from an east or west window; no hot direct sun | When the top 1–2 in. are dry; about every 7–10 days; less in winter | Moderate | ASPCA: toxic to dogs, cats and horses (insoluble calcium oxalates) |
| Areca palm | Bright indirect: 2–5 ft from an east or west window, 4–8 ft back from a south window; brief morning sun is fine | When the top 1 in is dry: about every 5–7 days in summer, 10–14 in winter; soft water | Moderate | Non-toxic to dogs and cats (ASPCA) |
| Boston fern | Medium-bright indirect; east window or filtered south/west light | Keep evenly moist; water when the surface just begins to dry | Moderate | Non-toxic to cats and dogs (ASPCA) |
| Dracaena | Bright indirect; 3–6 ft from a south window or near an east/west one; green types tolerate medium light, variegated need more | When the top 1.5–2 in are dry: every 5–7 days in summer, 12–18 days in winter; rain, distilled or RO water | Easy | Toxic to cats and dogs: saponins (ASPCA) |
| Peace Lily | Bright indirect light for blooms; tolerates low light (no direct midday sun) | When the top 1 inch is dry or leaves begin to sag; every 5–7 days in summer, 10–14 in winter | Easy | Toxic to dogs and cats per ASPCA (insoluble calcium oxalates) |
| Philodendron | Bright indirect; heartleaf tolerates low light | When the top 1-2 inches are dry; about every 7-10 days in summer | Easy | Toxic to cats, dogs and horses (ASPCA) |
| Snake plant | Low to bright indirect; tolerates some direct sun | When soil is fully dry: every 2–3 weeks summer, 4–8 weeks winter | Easy | Toxic to cats and dogs (ASPCA): saponins |
| Spider plant | Bright indirect; tolerates medium light | When top 1 inch is dry: ~weekly summer, every 10–14 days winter | Easy | Non-toxic to cats and dogs (ASPCA) |
Few houseplant claims are repeated as often as "this plant purifies the air." Plant tags, store displays and countless lists say so, almost always citing NASA. Here is what the research actually shows.
Where the claim comes from
In 1989, B. C. Wolverton and colleagues at NASA's Stennis Space Center published Interior Landscape Plants for Indoor Air Pollution Abatement. They placed common houseplants in sealed Plexiglas chambers of roughly 0.4 to 0.9 cubic meters (about 15 to 31 cubic feet), injected chemicals such as benzene, formaldehyde and trichloroethylene, and measured how fast the levels dropped. The plants and their potting soil did reduce the chemicals. The study was designed with sealed environments such as space habitats in mind.
From that, a list of plants, including peace lily, snake plant, spider plant, pothos, English ivy and dracaena, spread as "NASA-approved air purifiers."
Why sealed chambers don't translate to your living room
A real room is not sealed. Air leaks in and out through gaps and is replaced by heating and cooling systems, open windows and exhaust fans. Pollutants are also emitted continuously, not injected once.
In 2019, Bryan Cummings and Michael Waring of Drexel University reviewed 12 published chamber studies in Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal efficiencies, published online in 2019 in the Journal of Exposure Science and Environmental Epidemiology. The median single plant cleaned only about 0.023 cubic meters of air per hour. They converted the 196 experimental results from those studies into a clean air delivery rate, the metric used for air purifiers, and compared it with ordinary building air exchange. The plants' effect was orders of magnitude smaller: by their estimate it would take 10 to 1,000 plants per square meter of floor space to match the air cleaning a building's normal ventilation already provides.
| Typical living room | |
|---|---|
| Plants on a few shelves | Effect on air too small to measure |
| Plants needed to match normal air exchange | Hundreds to thousands |
| An open window or running exhaust fan | Replaces a large share of the air within hours |
What actually improves indoor air
The EPA's guide to air cleaners in the home puts the order of priorities as: reduce or remove pollution sources, ventilate with outdoor air, and then use an air cleaner as a supplement. In practice:
- Control sources: no smoking indoors, ventilate when cooking on a gas stove, choose low-VOC paints and finishes, and air out new furniture.
- Ventilate: open windows when outdoor air is good, run kitchen and bathroom exhaust fans.
- Filter: a portable air cleaner with a HEPA filter sized for the room, and a good HVAC filter.
Should you still grow these plants?
Absolutely, just for the right reasons. The plants on the classic lists happen to be some of the toughest houseplants available:
- Peace lily: blooms in modest light.
- Snake plant and ZZ plant: nearly care-free.
- Spider plant: fast, pet-safe.
- Pothos and philodendron: easy trailing plants.
- Dracaena and rubber plant: larger statement plants.
- Boston fern and areca palm: pet-safe greenery for brighter, humid rooms.
One caution: several of these are toxic to cats and dogs, per the ASPCA plant list, including peace lily, snake plant, pothos, philodendron and dracaena. See pet-safe plants if you have pets, and easy houseplants for more beginner-friendly picks.
Often mislabeled: plants that don't belong here
| Plant | Why it doesn't really fit |
|---|---|
| Any plant sold as a replacement for an air purifier | No houseplant, at any realistic number, matches the effect of ventilation or a HEPA filter. |
| Plants as a fix for mold or radon | Plants do nothing for these; moist potting mix can even add to mold spores and fungus gnats. |
Frequently asked questions
Do air-purifying plants really work?
What did the NASA clean air study actually find?
How many plants does it take to purify a room?
What actually improves indoor air quality?
Is there any benefit to having plants indoors?
Sources
Facts on this page were checked against these publications. Links open in a new tab.
- ASPCA Toxic and Non-Toxic Plant List www.aspca.org
- epa.gov www.epa.gov
- Nature Portfolio www.nature.com
- ntrs.nasa.gov ntrs.nasa.gov