---
title: "Air Purifying Indoor Plants: What the NASA Study Really Found"
description: "The 12 plants from NASA's clean air study, what they actually remove, and the honest arithmetic on how many you would need to change the air in a real room."
url: https://upflat.online/blog/air-purifying-indoor-plants
category: air-wellbeing
tags: ["air purifying", "plant picks", "research", "indoor plants"]
published: 2026-01-22
updated: 2026-08-25
author: "Mara Ellis, Horticulturist & founder"
reading_time_minutes: 5
license: "Quotation permitted with attribution and a link to the source URL."
---

# Air Purifying Indoor Plants: What the NASA Study Really Found

**Short answer:**

- Houseplants do remove VOCs — but only in sealed laboratory chambers, not in a ventilated room.
- You would need roughly 10–1,000 plants per square metre to match opening a window.
- Keep peace lilies, areca palms and snake plants because they are good plants, not as air filters.

## Key takeaways

- The famous NASA result is real — but it was measured in sealed chambers, not in homes.
- Later analyses put the clean-air delivery rate of a houseplant far below that of ventilation.
- Plants do measurably raise humidity and lower reported stress, which are genuine benefits.
- Buy these plants because they are tough and handsome; treat air cleaning as a bonus, not a reason.

Almost every air purifying plant list you have ever read traces back to one source: a 1989 NASA study by B.C. Wolverton, which tested houseplants in sealed chambers for their ability to remove benzene, formaldehyde and trichloroethylene. The results were striking and they have been repeated ever since — usually without the one caveat that changes everything, which is that a sealed 0.9 m³ chamber is not a living room. I went and read the original paper, and then the reanalysis, because the gap between the two is the whole story.

## The 12 plants NASA tested well

*Compounds each species removed in the original chamber trials.*
| Plant | Botanical name | Removed in testing | Difficulty |
| --- | --- | --- | --- |
| Peace lily | Spathiphyllum wallisii | Benzene, formaldehyde, TCE, xylene, ammonia | Easy |
| Areca palm | Dypsis lutescens | Formaldehyde, xylene, toluene | Moderate |
| Snake plant | Dracaena trifasciata | Benzene, formaldehyde, TCE, xylene | Very easy |
| Spider plant | Chlorophytum comosum | Formaldehyde, xylene | Very easy |
| Money plant / pothos | Epipremnum aureum | Benzene, formaldehyde, xylene | Very easy |
| Boston fern | Nephrolepis exaltata | Formaldehyde, xylene | Moderate |
| Rubber plant | Ficus elastica | Formaldehyde | Easy |
| Dracaena 'Janet Craig' | Dracaena fragrans | Benzene, formaldehyde, TCE | Very easy |
| Aloe vera | Aloe barbadensis | Formaldehyde, benzene | Easy |
| Chrysanthemum | Chrysanthemum morifolium | Benzene, formaldehyde, ammonia | Short-lived indoors |
| Gerbera daisy | Gerbera jamesonii | Benzene, TCE | Difficult |
| Bamboo palm | Chamaedorea seifrizii | Formaldehyde, benzene | Easy |

## What the numbers actually say

In 2019, researchers at Drexel University reanalysed a dozen chamber studies and converted the results into clean air delivery rate — the standard measure used for air purifiers and ventilation. Their conclusion was blunt: the rate achieved by potted plants is one to three orders of magnitude below the effect of ordinary building ventilation. To match the air exchange already happening in a normal room, you would need somewhere between ten and a thousand plants per square metre of floor space.

> **The honest summary**
> Houseplants do remove VOCs. They just do it slowly, in a room that is simultaneously exchanging its entire air volume with outdoors several times an hour. Opening a window for ten minutes does more than a room full of plants does in a day.

## What plants genuinely do to indoor air

- **Raise humidity.** Transpiration from a group of larger plants measurably lifts relative humidity in a room, which helps with dry winter air, static and irritated sinuses.
- **Lower perceived stress.** This is the best-supported finding: studies of planted offices and hospital rooms consistently report improved mood, comfort and concentration.
- **Absorb some particulate matter** on leaf surfaces — which is one argument for dusting leaves rather than leaving them.
- **Slightly increase CO₂ at night** in most species — trivially small, and not a health concern.

**Figure: Sealed chamber vs your living room**

The same finding, at two scales. The chamber result is real; the room result is what you actually live in.

## If air quality is the actual goal

1. **Ventilate** — Open windows on opposite sides of the home for ten minutes twice a day. This does more for VOC and CO₂ levels than any other intervention, free.
2. **Remove the source** — New furniture, paint, adhesives, air fresheners and scented candles are the main indoor VOC sources. Airing new furniture before it comes inside is more effective than filtering afterwards.
3. **Use a HEPA filter for particulates** — A HEPA unit sized for the room genuinely removes PM2.5 — relevant in cities with high outdoor pollution, where opening the window is not the answer.
4. **Add an activated carbon filter for VOCs** — Carbon adsorption is the mechanism plants use, done at scale. This is what actually replicates the chamber results in a real room.
5. **Then add plants** — For the humidity, the stress reduction and the fact that a room with plants in it is a nicer room. Just not as the air quality strategy.

## For homes in high-pollution cities

In cities where outdoor PM2.5 is regularly above safe limits — much of northern India during winter, among others — the ventilation advice inverts: opening windows at peak pollution brings the problem in. There the practical answer is a HEPA purifier sized to the room, running during the worst hours, with ventilation timed to cleaner parts of the day. Plants remain a pleasant addition; they do not filter particulates at any meaningful rate.

> **Choose by growing conditions, not by the list**
> Every plant in that table is a good houseplant on its own merits. Pick the ones that match your light — snake plant and pothos for [dim rooms](/blog/low-light-indoor-plants), areca palm and peace lily for bright indirect light — and ignore the ranking, which was never about your room in the first place.

## Frequently asked questions

### Do indoor plants really purify the air?

They remove volatile organic compounds in sealed chamber experiments, but the effect in a ventilated home is negligible. A 2019 reanalysis found you would need between ten and a thousand plants per square metre to match the air exchange a normal room already has.

### Which indoor plant purifies air the most?

In the NASA chamber trials the peace lily removed the widest range of compounds, followed by the areca palm and Dracaena 'Janet Craig'. In real rooms the differences between species are far smaller than the difference made by opening a window.

### How many plants do I need to purify a room?

Far more than is practical — estimates from the Drexel reanalysis range from ten to a thousand plants per square metre of floor space. For actual air cleaning, use ventilation and a HEPA or activated carbon filter.

### Are air purifying plants worth buying?

Yes, for reasons other than air chemistry. They raise humidity, improve reported mood and concentration, and the species on the NASA list happen to be among the toughest and most attractive houseplants available.

### Which air purifying plants are best for India?

The areca palm, money plant, snake plant and peace lily are all widely available, suit warm interiors and tolerate the light levels of a typical apartment. In cities with high winter PM2.5, pair them with a HEPA purifier rather than relying on them.

## Sources

- Interior landscape plants for indoor air pollution abatement — NASA Technical Reports Server, 1989. https://ntrs.nasa.gov/citations/19930073077
- Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal efficiencies — Journal of Exposure Science & Environmental Epidemiology, 2020. https://www.nature.com/articles/s41370-019-0175-9
- Indoor Air Quality (IAQ) — US Environmental Protection Agency. https://www.epa.gov/indoor-air-quality-iaq
- Houseplants — Royal Horticultural Society. https://www.rhs.org.uk/houseplants

---

Source: https://upflat.online/blog/air-purifying-indoor-plants — Upflat, written by Mara Ellis, reviewed 2026-08-25.