10 March 2011 – The claims for green plants in buildings are that they help to improve indoor life. From a single plant on a desk, container plants throughout the space, planted foyers, to landscaped atriums and bioclimatic skyscraper plantings, the presence of plants creates a healthy and pleasant work environment.

How do they do this? Following are some answers to the unasked questions about plants

VOCs

Plants reduce and remove the harmful pollutants in indoor air, such as volatile organic compounds. They are an inexpensive complement to conventional air filter systems, helping to provide cleaner air. They also contribute to relative humidity stabilisation and improve the oxygen/carbon dioxide exchange (O²/CO²). Another benefit is that they reduce glare and provide a restful effect on eyes.

Plants can be used to address acoustic problems and they do not interfere with any existing air distribution systems or patterns in a room. Plants entail relatively minor capital and running costs, and are an important element in privacy screening in open plan offices. Plants are stress busters,creating a healthy and pleasant work environment, contributing to productivity.

Not a source of allergens

It’s a myth that plants are a source of allergens and have any effects on indoor air microorganisms . People are the most significant source of indoor microorganisms. Plants do not pose a threat to the health of building occupants.  A study by the Department of Internal Medicine, University of Michigan concluded that “healthy, undisturbed house plants do not constitute a major exposure source for airborne fungus spores.” There was also little evidence of airborne pollen from flowering plants such as cyclamen, begonias and Impatiens, despite disturbance by watering and a circulation fan.

Kuopio Regional Institute of Occupational Health in Finland also reported no increase in the concentration of indoor air microorganisms in offices after the introduction of plants, which were evaluated over a 12 month period.

Restoring humidity balance

Plants can help restore balance to humidity levels.  They are naturally self-regulating, with mechanisms for moisture conservation. In many buildings, especially during the winter months, the relative air humidity is very low, often less than 30 per cent.  In low relative air humidity, plants  help to achieve a comfortable level of humidity and reduce their evaporation when the relative humidity is high.

Vacuum cleaners cause dust

One of the prime sources of dust in offices is the vacuum cleaner.  Fifty per cent of the air breathed  in offices comes from the floor.  Plants indoors function as natural dust filters, capturing and removing dust from the air.

Not infection carriers

Removing plants and flowers from patient’s rooms overnight has been a past practice because of a  misunderstanding of plant respiration despite no evidence that healthy plants are a problem. When the renal dialysis ward of a large Sydney hospital had a major infection problem, one of the first steps was to remove the plants. However investigations showed that the transmission of microorganisms was from visitors handling the patient’s bed-end charts and from this to the nursing staff.

A study of personnel working in a hospital radiology department showed  a 25 per cent decrease in complaints after the introduction of indoor foliage plants and full-spectrum lighting. There were significant reductions for headache (45 per cent), feeling heavy-headed (33 per cent), fatigue (32 per cent ), dry, hoarse throat (22 per cent ) and dry/itching skin on hands (21 per cent).

Concentration of fungal spores did not change due to the introduction of plants and improved lighting. The radiology department director reported that short-term absence due to illness decreased from a usual 15 per cent to five per cent during the experimental period. With the plants remaining in the room this decreased rate has persisted for more than five years.

Office productivity tested

Studies have shown that productivity declines by about 12 per cent when health and comfort are threatened.  A study in the Netherlands in 2001 involving 250 employees in a tax office building using a control group (without plants) and a test group (with plants) found that the test group rated well-being more favourably than the control group. The same applied to the ratings for the quality of the working area. The strongest link was found with those working on computers in the test group, as their wellbeing, concentration and thus efficiency improved. Other environmental factors included reduction in static electricity. Even one plant –correctly lit –makes a small contribution to reduction of CO2 concentrations.

A Norwegian cross-over study among 51 offices over two three-month periods evaluating the effects of indoor plants on health and well-being of occupants, found significant reductions in incidence of symptoms such as coughing (37 per cent), fatigue (30 per cent), dry, hoarse throat and dry or itching facial skin (23 per cent). The score sum, as a mean of 12 symptoms, was 23 per cent lower during the period when the participants had plants in their offices than when there were none.

Simple solutions are best

It is always preferable to adopt a preventative approach and provide the conditions for a healthy productive work environment. Plants are a cost-effective, simple solution.

Dr Ronald Wood is a director of Innovative Plant Technology Pty Ltd and has more than 30 years

experience with all aspects of interior/exterior landscapes, in Australia, North America, Europe

and Japan. He is an environmental scientist, acknowledged for pioneering research in the role of

plants in the indoor environment for the reduction of air-borne volatile organic contaminants. He

has advised on a number of major office buildings including Melbourne City Council’s C.H2 Contact:

iplant@plantscleanair.com