There was an article on this topic in Building Green recently that presented a different perspective. It was sort of non-committal, but basically said that indoor plant benefits linked to performance (cleaner air, less ventilation required) haven’t been well documented. Here is a stronger negative statement from Hal Levin, one of the experts quoted in the BG article. He is responding to the BG article:

Indoor plants — too much “myth” and wishful thinking Posted by Hal Levin on Sep 28, 2008, 05:27 PM
The article paints a considerably rosier view of the role of plants indoors than the scientific evidence can support.

Much if not most of the research supporting the use of plants to improve indoor air quality or enhance productivity have been funded by the companies that provide (sell or rent) plants and the systems in which to install them. Objective evidence of their ability to clean indoor air or enhance productivity is still lacking.

Everyone likes plants and wants to believe that they are good for us, but the must be installed and maintained with great care to avoid elevating moisture to unhealthy levels. Otherwise, they can elevate moisture excessively and, thus, promote mold growth or lead to adverse health effects that have been associated with elevated moisture levels indoors.

Claims for their ability to remove pollutants from indoor air are based on very weak science, at best, and even if one accepts that science, the removal rate is extremely low compared even to the removal by envelope leakage in a reasonably energy-conserving house or office building.

Since having plants around do tend to make most of us feel better, they may be associated with increased satisfaction with the indoor environment. But, it is a great stretch in the Carnegie-Mellon analysis: “Assuming a 2.3% improvement in productivity per employee…” Neither Fjeld et al nor Lohr et al measured productivity at all. Lohr’s study was done in a windowless environment to see if the addition of plants would reduce stress levels.

This level of statistical precision misleads us into thinking that the evidence on which it is based is far more scientifically valid and reliable than is actually the case. The links between indoor environmental quality (or occupants’ perception of it) and productivity are far weaker than those between one’s satisfaction with salary, work, relationship with supervisors, job security, and many factors in one’s personal life.

We reviewed the literature on the ability of plants to clean indoor air 16 years ago — the article can be found on my web site — and a more recent examination of the literature provides no more evidence of the efficacy of plants to remove indoor air pollutants.

Use of plants indoors to create a more pleasant environment is a great idea if it is done carefully. But assuming that it can clean the air or enhance productivity is unwarranted at this time.

Hal Levin