The NASA Clean Air Study: What It Really Found
In 1989, NASA scientists led by Dr. B.C. Wolverton published a study that would change how millions of people think about houseplants. The study, conducted in sealed test chambers, found that certain houseplants could remove significant quantities of volatile organic compounds (VOCs) — including formaldehyde, benzene, and trichloroethylene — from the air.
The study sparked a houseplant revolution. But what does the research actually say about plants as air purifiers in real homes? And which plants are most effective?
The honest answer is nuanced. The NASA study was conducted in small, sealed chambers — very different from a typical home with its air exchanges, ventilation systems, and much larger volumes. A 2019 meta-analysis published in the Journal of Exposure Science & Environmental Epidemiology found that you would need between 10 and 1,000 plants per square metre to match the air-cleaning effect of simply opening a window.
However, this doesn't mean air-purifying plants are useless. In poorly ventilated spaces — sealed offices, rooms with limited air exchange, or spaces with specific VOC sources — plants can make a meaningful contribution to air quality. And the biophilic benefits of plants — stress reduction, mood improvement, and increased wellbeing — are well-established regardless of their air-cleaning capacity.
The Best Air-Purifying Plants
Based on the NASA study and subsequent research, these plants have the strongest evidence for VOC removal:
Peace Lily (Spathiphyllum)
Consistently ranked as one of the most effective air purifiers, removing formaldehyde, benzene, trichloroethylene, xylene, and ammonia. It also increases room humidity, which can reduce the concentration of airborne dust and allergens. Thrives in low to medium light. Note: toxic to cats and dogs.
Spider Plant (Chlorophytum comosum)
One of the safest air-purifying plants for homes with pets and children. Effectively removes formaldehyde and xylene. Produces "spiderettes" that can be propagated easily. Thrives in a wide range of light conditions.
Snake Plant (Sansevieria trifasciata)
Removes formaldehyde, benzene, trichloroethylene, xylene, and toluene. Uniquely, it converts CO2 to oxygen at night (most plants do this during the day), making it particularly valuable in bedrooms. Extremely drought-tolerant.
Boston Fern (Nephrolepis exaltata)
One of the most effective plants for removing formaldehyde and xylene. Also acts as a natural humidifier, releasing moisture into the air. Requires more care than most air-purifying plants — it needs consistent moisture and humidity.
Bamboo Palm (Chamaedorea seifrizii)
One of the highest-rated plants in the NASA study for overall air purification. Removes formaldehyde, benzene, and trichloroethylene. Adds a tropical, biophilic quality to any space. Tolerates low light.
Rubber Plant (Ficus elastica)
Particularly effective at removing formaldehyde. Its large, glossy leaves are visually striking and make a strong biophilic statement. Prefers bright indirect light.
Aloe Vera
Removes formaldehyde and benzene (often found in paint and cleaning products). Also provides a practical benefit — the gel inside its leaves soothes burns and skin irritation. Needs bright light and infrequent watering.
English Ivy (Hedera helix)
Research has shown that English ivy can reduce airborne mould particles by up to 60% in 12 hours — making it particularly valuable for people with allergies or asthma. Effective at removing formaldehyde. Can be grown as a trailing plant or trained up a trellis.
How Many Plants Do You Need?
For meaningful air quality improvement in a typical room (approximately 15–20 square metres), research suggests a minimum of 15–20 medium-to-large plants. This is more than most people have, but it's achievable with a combination of floor plants, shelf plants, and a small living wall.
A more practical approach is to focus on the rooms where air quality matters most — bedrooms (where you spend 7–9 hours breathing the same air), home offices (where you spend long periods), and any rooms with specific VOC sources (new furniture, fresh paint, or synthetic carpets).
Use our Air Quality Plant Selector to find the best plants for your specific air quality concerns and room conditions.
Maximising Air-Purifying Effectiveness
To get the most from your air-purifying plants:
Keep leaves clean: Dusty leaves are less effective at both photosynthesis and VOC absorption. Wipe large leaves monthly with a damp cloth.
Ensure healthy root systems: The majority of VOC absorption actually occurs in the soil and root zone, not the leaves. Healthy, active root systems are essential for effective air purification.
Avoid overwatering: Waterlogged soil can harbour mould, which may worsen air quality. Allow soil to dry appropriately between waterings.
Combine with ventilation: Plants work best as a complement to good ventilation, not a replacement for it. Open windows when possible, and use plants to maintain air quality in between.
Frequently Asked Questions
Do air-purifying plants actually work? Yes, but with caveats. In sealed or poorly ventilated spaces, plants can meaningfully reduce VOC concentrations. In well-ventilated homes, their air-cleaning effect is more modest. Their biophilic benefits — stress reduction, mood improvement — are well-established regardless.
Which plant removes the most toxins? The peace lily (Spathiphyllum) and bamboo palm (Chamaedorea seifrizii) consistently rank highest in studies for overall VOC removal across the widest range of compounds.
Are air-purifying plants safe for pets? Many are not. Peace lily, pothos, snake plant, and rubber plant are all toxic to cats and dogs. Safe alternatives include spider plants, Boston ferns, bamboo palms, and areca palms. Always verify before bringing a new plant into a home with pets.
Can plants help with allergies? Some plants, particularly English ivy, have been shown to reduce airborne mould particles. However, some people are allergic to plant pollen or mould in potting soil. If you have allergies, choose low-pollen plants and use well-draining, mould-resistant potting mixes.
