Photosynthesis Basics

• Green plants create their own food through the process of photosynthesis. The process starts when natural or artificial light hits the leaves of the plant and interacts with the chlorophyll, which is what makes the leaves green. This interaction causes the plant to separate stored water into its basic components. The leaves of the plant take in carbon dioxide through tiny holes called stomata, where it is combined with energy stored in the plant's cells to produce a simple sugar. The byproducts of this process, unused oxygen and water vapor, then leave the plant through the stomata. Through the process of photosynthesis, plants take in carbon dioxide and release oxygen, essentially cleaning the air we breathe.
  
  

Humidity

• Because plants release water vapor along with oxygen during photosynthesis, they can increase humidity in enclosed spaces. Air conditioners and central heat both dry the air in office buildings and homes. Indoor plants can help to re-humidify the air. A study by Washington State University found that the humidity in two rooms without plants was below the range recommended for human health and comfort (30 to 60 percent). Adding plants was found to increase the humidity significantly, from 25 to 30 percent in one instance, enough to raise it to the range beneficial for humans, but not excessively enough to cause concern of over-humidifying or water damage.
  
  

Dust

• Another Washington State University study found that the amount of dust particles in the air of a computer lab were significantly reduced by adding houseplants. This study concluded that adding plants to a room reduced the amount of dust settling on surfaces by as much as 20 percent. In a computer lab especially, these results are significant, because excessive dust buildup can damage computer hard drives.
  
  

Volatile Organic Compounds

• In 1973, NASA scientists tested the air inside the Skylab space station, identifying 107 VOCs, including formaldehyde, benzene and trichloroethylene. VOCs are spread through "off-gassing" in low levels by synthetic building materials. These three VOCs are known irritants and potential carcinogens. With the rise of energy-efficient buildings, "sick building syndrome" became more and more common. NASA conducted a study to determine if houseplants could remove formaldehyde, benzene and trichloroethylene from the air and improve air quality enough to alleviate sick building syndrome, for use in both energy-efficient buildings and space stations.
  
  

NASA Study Results

• In 1989, NASA released the results of that study. All plants in the study reduced a percentage of each of the three VOCs tested. For example, the ficus reduced formaldehyde by 47.4 percent, benzene by 30 percent and trichloroethylene by 10.5 percent. Some plants were more effective against a particular VOCs, but all tested plants were at least minimally effective against all three VOCs. Overall, the study found that common houseplants with low light requirements were able to remove trace organic pollutants from the air, especially in energy-efficient buildings. To be most effective, the lower leaves need to be pruned to expose the root-soil zone to air as well.