Do Terrariums Really Clean the Air? A Terrarium Expert Weighs In

The claim surfaces regularly in lifestyle content and plant shop conversations alike: houseplants clean the air, and terrariums, being concentrated plant environments, do this especially well. It is an appealing idea, and one we hear often. At J2 Terrarium, we have been asked this question enough times. That’s why we thought we’d answer it here properly.

The short answer is yes—but with meaningful caveats. This is what the science actually says, and what it means for the terrarium sitting on your desk.

Where the Claim Comes From

The air-purifying plant narrative traces back to a 1989 NASA study that found certain houseplants could remove volatile organic compounds (benzene, formaldehyde, trichloroethylene) from sealed test chambers. The study was widely reported, frequently cited and has since become one of the most referenced pieces of research in the houseplant industry.

What gets omitted in most retellings is the context. The NASA chambers were small, sealed and contained far higher concentrations of pollutants than any typical indoor environment. In other words, it was nothing like a living room or office in Singapore. Subsequent research has consistently found that the rate at which houseplants remove pollutants in real indoor settings is negligible when compared to the air exchange that occurs simply by opening a window or running a ventilation system.

A 2019 review published in the Journal of Exposure Science and Environmental Epidemiology concluded that you would need between 10 and 1,000 plants per square metre of floor space to match the air-cleaning effect of standard building ventilation. Needless to say, that goes beyond the means of a terrarium on the shelf. That is the work of a whole forest.

What Terrariums Do to Indoor Air

The more honest but nonetheless interesting answer is that terrariums do affect the air around them, although not primarily through pollutant removal.

Plants absorb carbon dioxide and release oxygen through photosynthesis during daylight hours. A closed terrarium with healthy, actively growing plants contributes a small but detectable amount of oxygen to its immediate environment. It will not meaningfully change the air quality of a room, but it is still a biological process occurring a metre from where you sit.

Humidity is another claim worth examining. A closed terrarium is largely a sealed system: moisture transpired by the plants cycles internally and rarely escapes into the surrounding room in any meaningful quantity. Open terrariums do release moisture more freely into their immediate environment, but their lower overall moisture retention means the effect remains modest. In both cases, the humidity contribution to the room at large is limited. 

Where terrariums do make a more convincing case for themselves, however, is not in what they do to the air—but what they do to the people breathing it.

The Benefit That Does Hold Up

A 2015 study in the Journal of Physiological Anthropology found that interaction with indoor plants. including simply having them in view, produces measurable reductions in physiological stress markers. Heart rate and blood pressure both decreased in participants who spent time near plants compared to those performing identical tasks in plant-free environments. The effect was consistent and statistically significant.

This is known as the biophilic response, a well-documented human reaction to the presence of living things that researchers believe is rooted in our evolutionary history as outdoor, nature-embedded creatures. The brain registers greenery and living systems as signals of a safe, resource-rich environment. The physiological result is a distinct shift towards calm. 

This is also why the size of the terrarium is secondary to its placement. Research into attention restoration theory suggests that even brief, incidental exposure to natural elements (a glance away from a screen, a moment of unfocused observation) is sufficient to produce a partial cognitive recovery. A small closed terrarium within eyeline does the same work as a large one. What matters, instead, is simply that it is there.

So, Should You Believe in the Air-Cleaning Claims?

We would treat them with scepticism when they appear in marketing material. 

The NASA research is credible but routinely misapplied, and the difference between a sealed laboratory chamber and a ventilated Singapore apartment is considerable. A single terrarium is not an air purifier.

What it is, however, is a living system that contributes to local humidity, produces oxygen through active photosynthesis and has a documented positive effect on the stress levels of the people around it. For a setup that asks 15 minutes of maintenance a month, that is a meaningful return.

Starting with the Right Build

A thriving terrarium that sustains healthy, actively growing plants always starts with the right substrate layering, drainage and plant selection. Our workshops guide participants through exactly this process, building closed terrariums designed to remain healthy and productive long after the session ends. Browse our available workshop dates and build something that earns its place on the shelf.

J2 Terrarium is where the science in this article becomes something you can take home.