Plants do not meaningfully purify the air in your home at densities you'd actually keep them. I'm going to explain why, cite the research, and then tell you about the ten plants from the original NASA study that are still worth growing — for reasons that have nothing to do with air filtration.

Disclosure: I buy what I recommend and test it personally. Amazon links may earn a commission at no extra cost to you — it does not affect picks. See the full affiliate disclosure.

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 sealed 0.73 cubic meter test chambers over 24 hours.

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 all published plant 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 93 and 1,000 plants per square meter of floor space. That is not a typo. Roughly 10 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. "The air exchange rate of a typical building is orders of magnitude faster than the clean-air delivery rate of plants," Cummings and Waring write.

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.

1. Peace Lily (Spathiphyllum)

Light: 50–200 fc indirect | Water: Weekly | 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 that I'd describe as genuinely multi-seasonal in its 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: 100–600 fc | Water: Every 1–2 weeks | 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 in about two weeks. One plant becomes ten in a season.

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: 25–500 fc | Water: Every 2–6 weeks | 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 secondary NASA claim: that they produce oxygen at night via CAM photosynthesis, making them ideal bedroom plants. I address this myth more fully in the bedroom plants guide, but the short version: the amount of oxygen a snake plant produces at night is 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: 50–600 fc | Water: Every 1–2 weeks | Pet safe: No | Difficulty: Very easy

Pothos appeared in later expansions of the NASA-adjacent plant-air-quality literature. It's the plant I recommend most frequently to 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: 25–300 fc | Water: Every 1–2 weeks | Pet safe: No | Difficulty: Easy

Chinese evergreen was among the better benzene-removal plants in the NASA chamber tests. 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 benjamina)

Light: 200–600 fc | Water: Every 1–2 weeks | Pet safe: No | Difficulty: Moderate

Ficus plants appeared in the NASA work as effective trichloroethylene and benzene absorbers under lab conditions. In real homes, the rubber plant's value is architectural: it grows into a proper tree (up to 10 feet indoors), has large glossy leaves that reflect light and make rooms feel livelier, and holds its form well.

The one frustrating thing about rubber plants: they hate being moved. Moving them triggers leaf drop. Find the spot with bright indirect light (at least 200 fc), put the plant there, don't rotate it, and leave it alone. They reward consistency. See rubber plant care.

7. Dracaena (Dracaena spp.)

Light: 100–400 fc | Water: Every 2–3 weeks | 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: 100–400 fc | Water: Every 1–2 weeks | 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: 100–400 fc | Water: Every 3–5 days | Pet safe: Yes | Difficulty: Moderate

Boston ferns were among Wolverton's best-performing plants for formaldehyde removal in lab conditions, and they've been cited specifically for their 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 practical benefit in very dry climates (under 30% RH) might be marginally noticeable.

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: 400–800 fc | Water: Every 2–4 weeks | Pet safe: No | Difficulty: Easy

Aloe appeared in the NASA study as effective for formaldehyde and benzene. 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 no VOC removal research on air plants, 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 appeared in some NASA research with decent removal rates for mold spores and airborne particulates in sealed conditions. The practical problem: English ivy is toxic to cats and dogs per the ASPCA, and it's invasive in most of North America. 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 the quantity of oxygen released by a household plant is not measurable in a human bedroom. It's genuinely not a factor in sleep quality.

Quick comparison table

PlantLightWaterPet safeSkill level
Peace LilyLow–mediumWeeklyNoEasy
Spider PlantMediumBiweeklyYesVery easy
Snake PlantLow–highEvery 2–6 wksNoVery easy
PothosLow–highBiweeklyNoVery easy
Chinese EvergreenLow–mediumBiweeklyNoEasy
Boston FernMediumEvery 3–5 daysYesModerate
Aloe VeraHighEvery 2–4 wksNoEasy

How to choose between these picks

If pet safety is your primary concern and you still want something from the NASA list, spider plant and Boston fern are the only clearly non-toxic options. 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 will die from a missed watering week or two.

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 roughly 10 plants per square foot — 93 to 1,000 per square meter — 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 do contribute measurable humidity through transpiration in small sealed or low-ventilation spaces. A big Boston fern or multiple large plants can raise the relative humidity by a few percent in a small dry room. That's about the limit of what plants do measurably for indoor air quality at normal densities.

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