Nat Hawes - Air-purifying Houseplants

In the late 80s, NASA scientists studied houseplants as a way of purifying the air in space facilities because the equipment used on the station, and even the astronauts themselves, produce gases and chemicals that can become concentrated and toxic over time. They were over the moon to discover that several plants filter out common volatile chemical compounds and these plants can also help clean the indoor air down here on Earth, which is typically far more polluted than outdoor air.

Plants absorb some of the particulates from the air at the same time that they take in carbon dioxide, which is then processed into oxygen through what is called photosynthesis. Photosynthesis is a two-step process, and the first step is when water is converted into oxygen. This first step directly requires light energy, which is captured by the photosynthetic pigments, mainly chlorophyll, in plant stems and leaves during daylight hours. The chlorophyll converts light energy (photons) into chemical energy, in the form of high-energy electrons. This chemical energy is used in the photosynthetic reaction centres to split two water molecules, producing four electrons, four protons, and two oxygen atoms, which combine to form oxygen gas (O2). The chemical energy captured in step one is then used in step two of photosynthesis - that is, to convert carbon dioxide (CO2) into carbohydrates (glucose). This glucose is then used in plant respiration or converted into starch and stored.

Most flowers and plants, except holy basil and mother-in-laws tongue, stop producing oxygen after dark and release carbon dioxide instead through respiration, though only at a minimal level. When plants photosynthesise, during daylight hours, most of them emit six molecules of oxygen and one of glucose for every six molecules of carbon dioxide they consume. When they respire, at night, this is reversed but since plants respire at a slower rate than they photosynthesise, there is a net gain of two to three molecules of oxygen per cycle. It is therefore perfectly safe to have a few plants in the bedroom at night. Holy basil and mother-in-laws tongue are two plants that are especially beneficial to have in the bedroom.

Houseplants can reduce, and even prevent, sick building syndrome, symptoms of which can include allergies, eye, ear and nasal irritations, dizziness, headaches and nausea. They can also reduce the risk of contracting colds and other viruses, decrease blood pressure, lift the mood, reduce mental fatigue and improve sleep. NASA research suggests having at least one plant per nine square metres (approximately100 square feet) of home or office space.

Growing plants in the home can be very beneficial to the health because not only can they remove airborne contaminants but some are also nutritious herbs for both medicinal and culinary use. Many also have volatile oils which can be used to clean the home and the body (see page .