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Plants do not meaningfully purify the air in your home at densities you'd actually keep them. This guide explains why, cites the research, and then covers the ten plants commonly linked to the NASA study that are still worth growing — for reasons that have nothing to do with air filtration.

The NASA Clean Air Study: what it actually showed

In 1989, NASA scientist B.C. Wolverton and colleagues published research testing whether plants could remove volatile organic compounds (VOCs) from sealed growth chambers. The results: yes, certain plants reduced levels of benzene, trichloroethylene, and formaldehyde in small sealed test chambers (roughly 0.4 to 0.9 cubic meters) over 24 hours, per the NASA report.

That's the whole study. Small sealed chambers. Highly concentrated initial VOC levels. Lab conditions unrelated to a lived-in home.

The internet took that finding and produced thirty years of articles claiming that keeping two or three houseplants would clean the air in your apartment. It does not work that way.

Why the 2020 Cummings & Waring research matters

In 2020, Bryan Cummings and Michael Waring published a systematic review in the Journal of Exposure Science and Environmental Epidemiology titled "Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal rates." Here's their core finding:

They modeled the VOC removal rates from 196 experiments in 12 published chamber studies against real indoor spaces with typical air exchange rates. Their conclusion: to achieve the same VOC removal that normal ventilation provides in a typical room, you would need between 10 and 1,000 plants per square meter of floor space. That is not a typo. That's roughly 1 to 93 plants per square foot.

The reason is simple: the air in your home is constantly exchanging with the outside. Your windows, gaps in the building envelope, and ventilation system move air in and out at rates that dwarf what a few potted plants can process. Cummings and Waring put it in terms of plant density: matching the VOC removal that "outdoor-to-indoor air exchange already provides in typical buildings" would take "10–1000 plants/m2 of a building's floor space."

This doesn't mean plants are useless. It means you should buy them for their actual benefits: aesthetics, psychological wellbeing, humidity contribution in dry climates, and — for some people — the demonstrated mood and attention-restoration effects of having live green things in a workspace. The air filtration claim is simply not supported at household plant densities.

What the NASA plants do genuinely well

The plants in Wolverton's 1989 study were selected for their ability to absorb VOCs in sealed lab conditions. They're also, not coincidentally, excellent houseplants. Here are the ten most commonly referenced, along with what actually makes each worth keeping. Most were in Wolverton's 1989 study; rubber plant and Boston fern were not, but they appear on nearly every "NASA plants" list.

1. Peace Lily (Spathiphyllum)

Light: Low to medium, indirect | Pet safe: No | Difficulty: Easy

The peace lily was one of Wolverton's top performers for benzene and formaldehyde removal in lab conditions. In a home, that research doesn't translate to measurable air quality improvement — but the peace lily is still one of the best flowering plants for low-light apartments, period. It blooms under fluorescent lighting, recovers visibly from drought (the dramatic wilt is a feature, not a bug), and it tells you exactly when it needs water.

It's also one of very few plants with genuinely multi-seasonal appeal: white spathes appear in spring and sometimes again in fall, and the dark glossy foliage looks good year-round.

Full guide: peace lily care.

2. Spider Plant (Chlorophytum comosum)

Light: Medium | Pet safe: Yes | Difficulty: Very easy

Spider plants appeared in the NASA study as effective formaldehyde removers in chamber conditions. What they're actually useful for in a home: they're the most forgiving propagation platform in the plant world. Each mature spider plant sends out runners with "spiderettes" — baby plants that root in water or soil; NC State Extension notes the plant "propagates easily by plantlets or division."

They're also non-toxic to cats and dogs, which is relatively rare among the plants in this category. If you have a pet-safe home and want something that thrives in a north-facing window and practically grows itself, spider plants are the correct choice.

See also: spider plant care.

3. Snake Plant (Sansevieria trifasciata)

Light: Low to high | Pet safe: No | Difficulty: Very easy

Snake plants made the NASA list and have since been cited in approximately every "best houseplants" article on the internet because of a claim that never came from the NASA study: that they produce oxygen at night via CAM photosynthesis, making them ideal bedroom plants. The bedroom plants guide covers this myth more fully, but the short version: snake plants take in CO₂ at night but make their oxygen during the day, and the amounts are negligible in any human-occupied space.

What snake plants genuinely do: tolerate more neglect than any other common houseplant, maintain architectural form in low-light corners, and look genuinely good in modern and minimalist interiors. That's enough reason to own one. See snake plant care.

4. Golden Pothos (Epipremnum aureum)

Light: Low to high | Pet safe: No | Difficulty: Very easy

Golden pothos (tested as Scindapsus aureus) was part of the 1989 NASA study and removed benzene well in the chamber tests. It's a strong first plant for people who are new to houseplants — not because it purifies air, but because it is genuinely impossible to kill through neglect, it looks good in both hanging baskets and on shelves, and it communicates clearly when it needs water (leaves get slightly limp and lose their gloss). See pothos care.

5. Chinese Evergreen (Aglaonema modestum)

Light: Low to medium | Pet safe: No | Difficulty: Easy

Chinese evergreen was one of the weaker benzene removers in NASA's initial chamber tests, though its removal rose sharply after several weeks of repeated exposure. In a house: it's one of the most underrated low-light foliage plants available, with cultivar options ranging from forest green to bright red-and-pink. The dark green solid varieties handle the lowest light; the brighter variegated ones need medium indirect light to hold their color.

6. Rubber Plant (Ficus elastica)

Light: Bright indirect | Pet safe: No | Difficulty: Moderate

The NASA work tested a different ficus (weeping fig, Ficus benjamina), and it removed little benzene or trichloroethylene in the chambers. In real homes, the rubber plant's value is architectural: it grows into a proper tree (NC State says it is usually kept to 2 to 10 feet indoors), has large glossy leaves that reflect light and make rooms feel livelier, and holds its form well.

One thing to know about rubber plants: NC State says they prefer to remain in one location. Find the spot with bright indirect light, put the plant there, and leave it alone. See rubber plant care.

7. Dracaena (Dracaena spp.)

Light: Low to medium | Pet safe: No | Difficulty: Easy

Multiple Dracaena species appeared in the NASA tests, with Dracaena marginata and D. fragrans being the most studied. In real use, dracaenas are excellent structural plants: they grow upright to several feet, tolerate low-medium light and sporadic watering, and have a wide range of leaf colors and forms. They're popular in offices precisely because they can tolerate the indifferent treatment most office plants receive.

One real chemical caution: dracaenas are sensitive to fluoride in tap water, which causes brown leaf tips. If you water with tap water in a fluoride-heavy area, the tips will discolor. Filtered or distilled water prevents this.

8. Heartleaf Philodendron (Philodendron hederaceum)

Light: Medium, indirect | Pet safe: No | Difficulty: Easy

Heartleaf philodendron was studied for its ability to remove formaldehyde from sealed chambers. In homes: it's one of the best easy-care trailing plants, grows faster than pothos in most conditions, and has a lighter, more papery leaf texture that looks different from the waxy shine of pothos. It's a reliable choice for shelves and hanging baskets, especially in medium indirect light.

See heartleaf philodendron care.

9. Boston Fern (Nephrolepis exaltata)

Light: Medium | Pet safe: Yes | Difficulty: Moderate

Boston fern wasn't part of the 1989 NASA report, but it's a fixture of air-purifying lists and is often cited for its ability to add moisture to indoor air (transpiration). The transpiration effect is real — large ferns genuinely release water vapor and can measurably raise humidity in smaller rooms — though this is trivially small compared to a humidifier.

The care challenge: they need consistently moist soil and high humidity. Brown fronds are almost always a dryness problem. In humid climates or humid rooms, they thrive with minimal intervention. In dry climates, they need a pebble tray or regular misting. See Boston fern care.

10. Aloe Vera (Aloe vera)

Light: High | Pet safe: No | Difficulty: Easy

Aloe appeared in the NASA study only in the formaldehyde tests, where it removed the least of any plant. At home, it's most useful as a first-aid plant: the gel inside fresh leaves has well-documented topical applications for minor burns and skin irritation. It's also one of the most drought-tolerant plants in this category — a succulent that stores water in thick leaves and wants bright indirect light and almost no watering attention in winter.

One important note: despite aloe's reputation as a wellness plant, NC State's Plant Toolbox classifies Aloe vera as problematic for cats and dogs with low severity if ingested.

Plants marketed as "air purifiers" that aren't on the NASA list

Tillandsia (Air Plants) — There's only a little VOC research on air plants (small chamber studies of formaldehyde uptake by their leaves), and they don't have soil, which eliminates the soil microorganism contribution that actually does some of the work in the NASA studies. They're beautiful objects that don't need pots, but "air purifier" is not a legitimate claim for them.

English Ivy (Hedera helix) — English ivy was the top benzene remover in one of the 1989 NASA chamber tests. (The often-repeated mold claim comes from a 2005 study by a teenager, presented at an allergy conference, not from NASA.) The practical problem: English ivy is toxic to cats and dogs per the ASPCA, and in natural areas it "smothers the ground, preventing native wildflower, shrub and tree seedlings from sprouting," per NC State Extension. The sealed-chamber results don't justify the household risks.

Snake Plant at night — This specific claim (that snake plants release oxygen at night and improve sleep quality) is a distortion of the CAM photosynthesis process. CAM plants do fix CO₂ at night, but they release oxygen during the day, and the amount from a household plant is not measurable in a human bedroom. It's genuinely not a factor in sleep quality.

Quick comparison table

PlantLightPet safeSkill level
Peace LilyLow–mediumNoEasy
Spider PlantMediumYesVery easy
Snake PlantLow–highNoVery easy
PothosLow–highNoVery easy
Chinese EvergreenLow–mediumNoEasy
Boston FernMediumYesModerate
Aloe VeraHighNoEasy

How to choose between these picks

If pet safety is your primary concern and you still want something from this list, spider plant and Boston fern are the only options classified non-toxic by the ASPCA. Peace lily, pothos, and snake plant are all toxic.

If low light is the constraint, peace lily and pothos are the most capable performers in genuinely dim conditions. Snake plant works even lower but grows slower.

If ease of care is the priority, snake plant and pothos win without competition. Neither is likely to die from a missed watering.

If you genuinely care about indoor air quality, the most evidence-based intervention is ventilation: open windows when possible, run a HEPA air purifier in sleeping areas, and choose low-VOC paints and finishes when renovating. A few potted plants are a pleasant addition to any of that, but they're not a substitute.

FAQ

Does the NASA study mean plants are useless for air quality?

Not entirely, but close enough for practical purposes. Cummings and Waring (2020) found that plants can remove VOCs, just not at the scale needed to matter in a normal ventilated room. You'd need 10 to 1,000 plants per square meter (about 1 to 93 per square foot) to match what normal ventilation already does. Normal ventilation almost always wins. Buy plants for aesthetics and wellbeing, not air filtration.

What does actually improve indoor air quality?

The most evidence-backed interventions: increase ventilation (open windows when outdoor air quality permits), use a HEPA air purifier in high-occupancy rooms, eliminate VOC sources (switch to low-VOC paints, clean with non-aerosol products), and control moisture to prevent mold. These interventions are documented to work at real-world scales. Plants are not.

Are there any plants that actually do anything measurable for air quality?

Large plants release water vapor through transpiration, which can add some moisture to the air in small sealed or low-ventilation spaces. That's about the limit of what plants do measurably for indoor air quality at normal densities.

Sources