New study confirms IAQ benefits of plants

Research teams at the University of Birmingham and the Royal Horticultural Society (RHS) have recently discovered that indoor plants may be able to reduce nitrogen dioxide (NO₂) by up to 20 per cent.

The team chose to use common houseplants in their research, including peace lilies, corn plants and fern arums. Each plant was placed in a test chamber, and was able to remove around half of the NO₂. The plants did this independently of their environment – for example, it didn’t matter if the soil was damp or the chamber was dark.

Lead researcher Dr Christian Pfrang says this is very different from the way indoor plants took up CO₂ in earlier studies. Previous studies have also been done into whether plants can purify the air, with mixed results.

It is unclear, however, exactly how the plants remove the NO₂.

“We don’t think the plants are using the same process as they do for CO₂ uptake, in which the gas is absorbed through stomata – tiny holes – in the leaves,” says Pfrang.

“There was no indication, even during longer experiments, that our plants released the NO₂ back into the atmosphere, so there is likely a biological process taking place also involving the soil the plant grows in – but we don’t yet know what that is.”

By the team’s calculations, the plants would be most effective in a smaller office environment. In a larger space, the effect would have a smaller mpact.

Principal horticultural scientist at the RHS and one of the researchers involved in the study, Dr Tijana Blanusa, hopes that understanding the limits of what to expect from plants can help them plan and advise on planting combinations that not only look good, but also provide an important environmental service.

The team will be continuing their work on a new research project funded by the Met Office, where they will test a broader range of variables for modelling indoor air quality.