Houseplants do release oxygen, but not enough to change the air in a home, and there is no good evidence that a reasonable number of them clean it. The U.S. EPA says so plainly, and a 2020 review of the research reached the same conclusion. The popular claims trace back to a 1989 NASA experiment run in sealed chambers. Plants are still worth growing. If you want five easy ones that most often appear on these lists, they are below, with honest notes on light, water, and pets.
Where the Claim Came From
In 1989, NASA researcher Bill Wolverton and colleagues tested a dozen common houseplants in sealed chambers to see whether they could remove household chemicals such as formaldehyde. They could. NASA's own account adds that the roots and the soil microorganisms did the bulk of the work, and that removing the leaves made only a small difference.
The finding was real, but it came from a small sealed box. Iowa State University Extension notes that this controlled setup does not directly translate to real homes, where air is constantly being replaced, even in new, airtight buildings.
What Later Research Found
A 2020 review in the Journal of Exposure Science & Environmental Epidemiology pulled together 12 published chamber studies and converted 196 results into a common air-cleaning measure. The median single plant removed pollutants at a rate of 0.023 cubic meters per hour. By the authors' calculation, matching the air exchange that a typical building already gets from outdoor air would take 10 to 1,000 plants for every square meter of floor space. The paper's title states the conclusion: potted plants do not improve indoor air quality.
The EPA is similarly direct: "There is currently no evidence, however, that a reasonable number of houseplants remove significant quantities of pollutants in homes and offices." It lists three approaches that do work: controlling the sources of pollution, improving ventilation, and using air cleaners or filtration. It describes source control as usually the most effective.
What About Oxygen?
Air is already about 21 percent oxygen. NOAA puts it at 20.946 percent of dry air. Plants do release oxygen while they photosynthesize, but a room's air is constantly exchanged with outdoor air, and none of the university or government sources we read claims that houseplants measurably change the oxygen level in a home. If your goal is more oxygen, houseplants are not the tool. Opening a window is.
So What Are Houseplants Good For?
Iowa State University Extension puts it simply: houseplants beautify the home and help you nurture a green thumb, even in the dead of winter. The authors of the 2020 review also point to well-being and productivity benefits as questions worth studying, which means that part is open rather than settled. A plant is a living thing to look after and look at. That is a good enough reason to own one.
If you want cleaner air, the EPA's advice is to reduce what is producing the pollution, ventilate, and filter when needed. Do not expect a plant to do any of those jobs.
Five Easy Plants Worth Having
These are the plants that most often turn up on "air-purifying" lists, and they are also forgiving, which is the real reason to buy them. We have included the pet-safety status of each from the ASPCA.
1. Snake plant (Dracaena trifasciata, formerly Sansevieria)
Why it earns a place: University of Wisconsin Extension says snake plants tolerate adverse conditions, need infrequent watering, and that overwatering is their main enemy. They are one of the easiest plants for a dim spot.
Pets: the ASPCA lists snake plant as toxic to dogs and cats. See our guide to snake plants and pets. You can browse our snake plants.
2. Spider plant (Chlorophytum comosum)
Why it earns a place: University of Wisconsin Extension says it grows easily indoors in medium to bright light, wants the soil to dry slightly between thorough waterings, and its thick, fleshy roots help it survive inconsistent watering. Brown tips have several causes, including salt buildup and fluoride or chlorine in tap water, so rainwater or distilled water can help.
Pets: the ASPCA lists spider plant as non-toxic to dogs and cats. Browse our spider plants.
3. Pothos (Epipremnum aureum)
Why it earns a place: University of Wisconsin Extension describes it as extremely easy and durable, happiest in filtered light, and best watered only when the soil surface is dry. Low light can cause variegated types to lose their pattern.
Pets: the ASPCA lists pothos as toxic to dogs, cats, and horses because of insoluble calcium oxalates. Browse our pothos.
4. Peace lily (Spathiphyllum)
Why it earns a place: Clemson Extension says peace lilies tolerate low light but grow best in bright indirect light, like soil that is moist but not soggy, and will wilt when the soil dries out. Lack of flowers usually means the plant is under a year old or is not getting enough light.
Pets: the ASPCA lists peace lily as toxic to dogs and cats. Browse our peace lilies.
5. Areca palm (Dypsis lutescens)
Why it earns a place: it brings a soft, feathery shape that the other four do not. Penn State Extension's guidance for indoor palms is bright, filtered light near a south- or east-facing window, soil kept moist but not wet, and a watch for brown frond tips in dry winter air and for spider mites. It asks a little more of you than the other four: steadier moisture and some attention to humidity.
Pets: the ASPCA lists areca palm as non-toxic to dogs, cats, and horses. See our areca palm.
Common Mistakes With "Air-Purifying" Plants
- Buying plants to fix a specific problem. If a room smells or feels stale, look for the source and ventilate. The EPA names these as the first steps.
- Overwatering to keep them "working." The EPA cautions that houseplants should not be overwatered, since wet soil can promote microorganism growth.
- Counting plants. The research gives no number of plants that clean a home. The review's range runs from 10 to 1,000 per square meter, which is not a realistic shopping list.
- Assuming "non-toxic" means harmless. The ASPCA notes that eating any plant material can cause vomiting and stomach upset in dogs and cats.
From the Greenhouse Bench
The honest pitch for a houseplant is the plant itself: its shape, its color, and the small routine of looking after it. The five above are good first plants because they tolerate ordinary indoor conditions, not because of anything they do to the air. If you have pets, check the exact botanical name against the ASPCA before you buy, using our pet-safe and toxic houseplant guide.
Frequently Asked Questions
Which houseplant produces the most oxygen?
None of the sources we reviewed ranks houseplants by oxygen output in a way that matters for a room. The amount is small compared with the oxygen already in the air, and air is constantly exchanged with the outdoors.
How many plants would I need to clean the air in my home?
A 2020 review calculated 10 to 1,000 plants per square meter of floor space to match the pollutant removal that typical ventilation already provides. That is why the EPA does not recommend plants as a way to control indoor air pollution.
Do air-purifying plants help with mold or smells?
The EPA's advice for both is to find and remove the source and to ventilate. It also notes that overwatered houseplants can promote microorganism growth, so a plant can make a damp problem worse.
Are air-purifying plants safe for cats and dogs?
It depends on the plant. Among these five, the ASPCA lists spider plant and areca palm as non-toxic to dogs and cats, and lists snake plant, pothos, and peace lily as toxic.
Should I buy an air purifier instead?
The EPA lists air cleaners and filtration as one of its three approaches, after source control and ventilation. It depends on what you are trying to remove from the air, so start with the source.
The Short Version
Do not buy a plant for oxygen or air cleaning. Buy one because you like it and can give it the light and water it wants. Any of the five above is a good place to start.
Sources: U.S. EPA: Improving Indoor Air Quality, Iowa State University Extension: Do houseplants actually improve indoor air quality?, NASA Spinoff: Plant Research Offers a Breath of Fresh Air, Cummings and Waring (2020), Journal of Exposure Science & Environmental Epidemiology, NOAA: Composition of the atmosphere, University of Wisconsin Extension: Dependable and Durable Houseplants, spider plant, pothos, Clemson Extension: Peace Lily, Penn State Extension: Palms as Houseplants, and ASPCA entries for snake plant, spider plant, pothos, peace lily, and areca palm. Photo: Annie Spratt on Unsplash.