It’s been more than 30 years since the now-famous NASA Clean Air Study demonstrated that houseplants can clear the air of chemical pollutants. The original idea of the study was to find ways to clean the air in space stations, where chemicals can build up. The results suggested that plants are not only effective in absorbing carbon dioxide and generating oxygen (via photosynthesis) they also provide a natural way of removing volatile organic compounds (VOCs) from the air.
VOCs are a group of chemicals that can be found in products in the home and workplace. They are emitted into the air we breathe from items such as paints, flooring, furniture, electronic devices and cleaning products. Examples of common VOCs include benzene, ethylene, formaldehyde and xylene. VOCs can be a danger to health when they build up to high levels. This is a particular problem in sealed areas such as space stations. But can also be of concern in homes and businesses where there is not enough ventilation, especially in the winter months.
In the NASA study, some plants were found to be very effective in absorbing VOCs from the air when tested in a sealed environment. Especially efficient plants included the Peace Lily (now the poster-plant for air purification), Lady Palm, Parlor Palm and Florist’s chrysanthemum. All of these plants were shown to absorb all six of the VOCs tested.
According to the NASA study, the optimal ratio of plants in indoor areas should be around one plant per 100 square feet (9.3m2). However, since then, studies in real life homes and offices have shown mixed results with normal indoor conditions, leading experts to suggest that the ratio of plants should be much higher. Some suggest there should be ten plants per square foot (0.09m2) – which is a dense level of coverage – in order to see results.
In reality, there are many variables, such as the level of gas in the air, the number and density of plants, and the surface area of the leaves and the VOC emitting products. It is clear that plants are capable of absorbing VOCs, the question is how effective they are in everyday, unsealed, environments.
As we know plants have many benefits, not just in absorbing pollutants but, for example, increasing a sense of wellbeing, improving productivity, and shortening healing times for patients. So it makes a lot of sense to bring plants inside and reap the benefits, even if the air purifying results are not yet fully defined.
Below is a list of plants, starting with those shown to be most effective at absorbing VOCs, from the NASA experiment. They are also easy-to-care-for houseplants so you can go ahead and enjoy your own indoor air quality (IAQ) experiment at home or in your workplace.
Peace Lily (Spathiphyllum)
This popular plant has long been a favourite amongst plant enthusiasts and is also one of the top performing plants from the NASA study. It can absorb VOCs, such as benzene and formaldehyde, and of course carbon dioxide. Its white blooms make it distinctive and easy to identify. In terms of care, peace lilies (or spathiphyllum), originate in tropical environments where they are found on the forest floor. So indirect light and moisture are important to keep them in optimum condition.
The Lady Palm or Rhapis Excelsa, is native to southeast Asia and can be found growing in the wild in Vietnam. It has been in use as an indoor plant for centuries, stemming from it’s popularity in Japanese palaces in feudal times. In the wild, the plant grows at an altitude of around 1000 meters and can also be found growing close to rivers. It likes shade and dry air and can manage with fewer waterings than many indoor plants. In the NASA Clean Air study this plant came in second place for its ability to filter most of the VOCs tested.
The Parlor Palm or Chamaedorea Elegans, as it is officially called, is a tropical plant that is native to the rainforests of Southern Mexico and Guatemala. It is one of the most popular house plants in the world. It was one of the top performers in the NASA study and can effectively remove all of the VOCs tested. Popular with the Victorians in the palm is still in vogue and provides a plant of sustainable size with it’s slow growth and relatively smaller size.
Chrysanthemums were one of the top performers in the NASA study and a later study showed they also filter ammonia and xylene from the air. These popular flowers, originating in China, have a beautiful bloom that can last for 4-6 weeks. They can flourish even in low light and are available all year round in an array of enticing colours. Just keep the pets away as they are toxic to animals and can cause irritation and sickness if ingested.