The NASA 1989 clean air study has been cited millions of times across the internet — and almost always oversimplified to "plants clean your air." The real story is more nuanced, more scientifically interesting, and ultimately more useful for making informed decisions about which plants to choose and how many to keep. Understanding what the study actually found changes the way you think about houseplants and air quality entirely.
The honest conclusion: plants do improve indoor air quality, but the effect in a typical home is smaller than popular articles suggest. The plants that perform best are well worth growing. And the real benefits of houseplants — which extend well beyond air filtration — are substantial and thoroughly documented. This guide covers it all: the science, the best plants, and why plants are worth having regardless of whether they transform your air quality overnight. See our complete best houseplants guide for additional recommendations across all categories.
The NASA Clean Air Study: What It Actually Found
The NASA clean air study, published in 1989 by B.C. Wolverton and colleagues, was conducted under very specific conditions: sealed chamber environments of approximately 17 cubic metres (smaller than most bedrooms), with high concentrations of specific volatile organic compounds (VOCs) pumped in. The study measured how effectively different plant species removed those VOCs from the sealed chamber air over a 24-hour period.
The study found that plants — and critically, the soil microbes living in their root zones — effectively removed benzene, formaldehyde, and trichloroethylene from the sealed chamber air. The soil microbes actually did much of the filtration work: when plants were tested without their soil (and therefore without their microbial communities), VOC removal rates dropped significantly. This is an important detail almost always omitted from popular summaries of the study.
The context that popular articles typically omit: the study was specifically designed for space station applications — small, sealed environments where air exchange with the outside is impossible. NASA needed to know whether plants could help maintain air quality in a sealed capsule. The 2019 follow-up research by Cummings and Waring at Drexel University calculated that in a typical home with normal air exchange (windows, doors, ventilation), you would need 100–1,000 plants per room to match the air purification effect of simply opening a window briefly. That's not a small caveat — it fundamentally changes the practical implications of the original study.
The honest scientific position: plants do remove VOCs from air. The effect in a real room with normal air exchange is measurable but modest — significantly smaller than the study implies when its sealed-chamber conditions are accounted for. A cluster of 10–20 plants in a room provides a real, if small, improvement in air quality. A single plant provides a very small improvement. Neither matches the dramatic air-purifying claims made in popular media.
How Many Plants Do You Actually Need?
The Cummings and Waring calculation gives us the uncomfortable truth about plant-based air purification: the number of plants needed to significantly clean a typical room's air is far beyond what any home plant collection would normally contain. Their estimate of 100–1,000 plants per room assumes a typical home with background air exchange rates — drafts, ventilation, doors opening and closing — that constantly dilute the effect any individual plant can have.
This doesn't mean plants are worthless for air quality — it means the claims need to be calibrated appropriately. A collection of 10–15 plants in a room provides a real, measurable benefit: a small but genuine reduction in VOC concentrations, some increase in oxygen production, and significant increases in humidity through transpiration. A single plant in a large room has a tiny effect, but it's not zero.
The practical implications: if you want plants primarily for air quality, you need many plants, not a few. A genuinely plant-dense room — every shelf, corner, and windowsill occupied — provides the most air quality benefit. For air quality improvement specifically, grow plants that are easy to propagate and multiply (spider plant, pothos) so you can build a large collection inexpensively. Any measurable air quality benefit from plants comes from quantity, not from any single specimen's superior performance.
The Top 10 Air-Purifying Plants
1. Peace Lily (Spathiphyllum)
The peace lily is the top overall performer in the NASA study, ranking among the highest for removal of benzene, formaldehyde, trichloroethylene, and additionally acetone and alcohol — a broader range of VOCs than any other plant tested. It combines this top-tier air-purifying performance with qualities that make it one of the most practically useful houseplants available: it thrives in low light (making it functional in rooms where most air-purifying plants would struggle), and it flowers reliably even without direct sunlight, producing elegant white spathes over a long season. See our complete peace lily care guide for all the details.
Peace lily also has one of the highest transpiration rates of common houseplants, contributing meaningfully to indoor humidity — particularly valuable in dry winter conditions when heating systems desiccate indoor air. Its large, dark green leaves provide substantial surface area for air filtration. For any room where you want to maximize the air-quality benefit from a small number of plants, peace lily is the single best choice.
2. Snake Plant (Sansevieria/Dracaena trifasciata)
Snake plant is one of the most frequently cited air-purifying plants — and for good reason. It performed strongly in NASA testing for formaldehyde removal, and its CAM (Crassulacean Acid Metabolism) photosynthesis pathway gives it a genuinely unusual property: unlike most plants, snake plant releases oxygen and absorbs carbon dioxide at night rather than during the day. This makes it one of the rare plants that genuinely improves bedroom air during sleeping hours. For the full story on snake plant's many benefits, see our snake plant benefits guide.
Beyond air purification, snake plant combines extreme drought tolerance with the ability to survive in very low light — making it the most genuinely low-maintenance option on this list. It can be neglected significantly without dying, making it the ideal plant for anyone who wants air quality benefits without committing to demanding plant care. It is also one of the most architecturally striking plants available — the upright, sword-shaped leaves in various shades of green, grey, and gold provide strong visual impact in any room position.
3. Golden Pothos (Epipremnum aureum)
Golden pothos demonstrated excellent formaldehyde removal in NASA testing, and its real-world value for air quality comes from a different angle: it's the easiest plant to grow in large quantities. Because pothos propagates so effortlessly — a stem cutting in water roots in 1–2 weeks — a single plant can become 10 plants within a season. This matters for air quality because, as established above, quantity of plants is the most important variable in achieving meaningful air quality improvement. For complete pothos care information, see our pothos care guide.
Pothos also tolerates the variable light conditions found throughout most homes, meaning you can place it in corners and positions where other air-purifying plants wouldn't survive. Fill those underused spots in a room with pothos, and you build toward a plant density that provides a real, cumulative air quality benefit. The trailing habit also allows single plants to cover large areas — a pothos trailing across a bookshelf occupies far more air-filtration surface area than a plant sitting in a single pot.
4. Spider Plant (Chlorophytum comosum)
Spider plant removes both formaldehyde and xylene from indoor air, and like pothos, it provides a practical air quality advantage through its extraordinary ease of propagation. A single healthy spider plant produces dozens of baby plantlets (spiderettes) each season, which root immediately when placed in moist soil. Within one growing season, a single spider plant can become 20 or 30 plants — all effective air purifiers. For spider plant care details, see our spider plant guide.
Spider plant is non-toxic to cats and dogs (unusual for an effective air-purifying plant — many NASA study performers are toxic), and it handles variable light conditions well. It is one of the very few plants that combines non-toxicity, easy propagation for building quantity, effective VOC removal, and genuinely easy care. For homes with pets, it becomes the top recommendation among air-purifying plants.
5. Dracaena marginata
Dracaena marginata tested positively for removing benzene, formaldehyde, trichloroethylene, and xylene — one of the broadest spectrums of VOC removal of any plant in the NASA study. Its tall, architectural form (narrow sword-like leaves on arching canes, reaching 1.5m+ in good conditions) also makes it one of the most visually impressive air-purifying plants. A large dracaena in a living room corner is both a statement plant and a genuine functional air-quality asset. For detailed care, see our dracaena care guide.
Dracaena marginata is also more tolerant of neglect and variable light than its dramatic appearance suggests. It prefers bright indirect light but handles medium light reasonably well. Water when the top half of the soil is dry, and it rewards minimal care with steady growth and good health. Avoid using fluoride-rich tap water (use filtered water or let tap water sit overnight) as dracaena is particularly sensitive to fluoride, which causes brown leaf tips.
6. Chinese Evergreen (Aglaonema)
Chinese evergreen removes benzene and formaldehyde from indoor air, and its practical advantage is exceptional tolerance for low light — arguably the most low-light-tolerant of all the plants on this list. It can survive in positions well away from windows where most other plants would fail. The wide variety of cultivars — ranging from deep green with silver markings to vivid red, pink, and orange varieties — also makes it one of the most decoratively versatile air-purifying plants. A collection of different-colored Aglaonema varieties in a dim corner provides both air quality benefit and striking visual interest.
Care for Chinese evergreen is straightforward: medium to low indirect light, water when the top half of the soil is dry, and avoid cold temperatures (below 15°C causes damage). Keep it away from cold drafts and heating vents. It grows slowly, meaning it stays in the same pot for extended periods without needing frequent repotting — a low-maintenance characteristic that makes it ideal for anyone who wants a set-and-forget air-purifying plant.
7. Bamboo Palm (Chamaedorea seifrizii)
Bamboo palm tested positively for benzene and formaldehyde removal in the NASA study, and it has an additional air quality benefit: one of the highest transpiration rates of any common houseplant. High transpiration means it releases significant amounts of water vapor into the air, naturally humidifying the room. In dry winter conditions when indoor humidity often drops below 30% (causing dry skin, irritated airways, and static electricity), a bamboo palm makes a measurable difference to indoor humidity levels.
Bamboo palm prefers bright indirect light and consistent moisture. It's more demanding than pothos or snake plant but rewards consistent care with lush, tropical fronds that create a dramatic, full canopy. Scale and spider mites are its most common pest problems — check the undersides of fronds regularly and treat promptly with neem oil or insecticidal soap if detected. A healthy bamboo palm growing in good conditions is a genuinely beautiful large-format houseplant as well as an effective air purifier.
8. Rubber Plant (Ficus elastica)
The rubber plant's large, glossy leaves — some varieties reaching 30–40cm per leaf — provide substantial surface area for VOC absorption, and it demonstrated effective formaldehyde removal in research studies. Its large leaf surfaces also make it one of the most effective transpiring plants by leaf area, contributing meaningfully to indoor humidity. In sizes from small table plants to large floor specimens, rubber plant provides scalable air quality benefit across different room sizes.
Rubber plant is more forgiving than its Ficus relative the fiddle leaf fig. It tolerates variable watering, handles medium light reasonably well, and doesn't drop leaves dramatically in response to being moved (as fiddle leaf fig notoriously does). Water when the top 3–4cm of soil is dry, provide bright indirect light for best growth, and wipe the large leaves occasionally with a damp cloth to remove dust that reduces photosynthetic efficiency — and also covers the leaf surface where VOC absorption occurs.
9. English Ivy (Hedera helix)
English ivy showed high effectiveness at removing benzene and formaldehyde in research studies, and some studies have also found it effective at reducing airborne mold spores — a different air quality benefit not related to VOCs. For anyone with mold sensitivity or living in a humid environment where mold is a concern, English ivy offers a genuinely distinct additional benefit compared to other plants on this list.
English ivy prefers cooler temperatures and good light — it thrives in bright indirect light or even some direct sun from an east-facing window. It struggles in hot, dry rooms (below 40% humidity causes significant leaf tip browning and increases spider mite vulnerability). For the best air quality results, grow it in a cool, bright position — a home office near a window, or a cooler bedroom — where it also happens to thrive naturally. As a trailing plant, it covers significant surface area relative to its pot size, maximizing its air-filtration impact.
10. Boston Fern (Nephrolepis exaltata)
Boston fern removes formaldehyde and xylene from indoor air, and alongside the bamboo palm, it is one of the most effective natural humidifiers among common houseplants. Its high transpiration rate significantly increases indoor humidity — valuable in dry winter conditions and for anyone with respiratory sensitivities to dry air. The lush, arching fronds also provide generous surface area for air filtration relative to the plant's footprint.
Boston fern is the most care-demanding plant on this list: it requires high humidity (above 50% ideally), consistent soil moisture (not drought, not waterlogged), and bright indirect light. A bathroom with a bright window is the ideal natural environment — the steam from showers provides exactly the humidity it needs. In drier rooms, a pebble tray filled with water beneath the pot or a humidifier nearby extends its happy range. For those willing to meet its needs, it is a spectacular, dramatically beautiful plant that also genuinely earns its air-purifying reputation.
VOCs: What Plants Actually Remove
Understanding which VOCs plants remove helps calibrate whether air-purifying plants address your actual indoor air quality concerns. The five VOCs most thoroughly studied in plant air purification research are: formaldehyde (emitted by furniture, flooring, adhesives, and many building materials — one of the most common indoor pollutants in modern homes), benzene (emitted by paints, plastics, synthetic fibers, and cigarette smoke), trichloroethylene (used in industrial solvents, dry cleaning fluids, and some adhesives), xylene (emitted by paints, lacquers, and adhesives), and ammonia (emitted by cleaning products and some fertilizers).
If your home is relatively new, just renovated, or has lots of new furniture (all of which off-gas formaldehyde for the first 1–3 years), the air-purifying benefits of plants are most relevant and actionable. If your home is older and well-ventilated, indoor VOC concentrations are typically lower to begin with, and the relative benefit of plants is smaller. Either way, the plants' other benefits — humidity contribution, psychological well-being, aesthetic value — remain constant regardless of your specific air quality baseline.
The Real Benefits of Indoor Plants (Beyond Air Quality)
The most thoroughly documented benefits of indoor plants have nothing to do with air filtration. Multiple well-controlled studies have found that the presence of plants in indoor environments reliably reduces cortisol levels (the primary stress hormone), improves mood and self-reported well-being, reduces anxiety, and improves focus and productivity in work environments. These psychological effects are robust — they appear across different study designs, different plant species, and different populations. They are not modest effects either: some studies show cortisol reductions of 15–20% in plant-rich environments compared to plant-free environments.
The mechanism is biophilia — the innate human affinity for natural environments and living things, shaped by hundreds of thousands of years of evolution in natural settings. Seeing plants triggers a relaxation response that staring at bare walls or screens does not. This is the reason hospitals with garden views have better patient outcomes, offices with plants have lower absenteeism, and homes with plants consistently rank higher in occupant satisfaction surveys. These benefits are real, substantial, and entirely separate from the air quality question.
The humidity contribution of plants is also a practical, measurable benefit. A collection of high-transpiring plants (Boston fern, bamboo palm, peace lily) in a room can increase relative humidity by several percentage points — enough to make a difference to dry skin, irritated airways, and comfort during dry winter months. This is a direct physical benefit that has nothing to do with the sealed-chamber VOC removal studies.
Frequently Asked Questions
The NASA clean air study is real science, and its findings are genuinely useful — as long as you understand what it actually measured and what its practical implications are for a real home. Plants improve indoor air quality: the effect is modest in typical rooms, real and cumulative with plant quantity, and most meaningful in new or recently renovated spaces with high off-gassing materials. The psychological and humidity benefits of plants are often more impactful in practice than the VOC removal. Grow plants you enjoy caring for, grow as many as your space allows, and trust that every plant contributes positively. Related guides: Snake Plant Guide, Peace Lily Care Guide, and our Best Houseplants Guide.