A joint researcher team from Korea and the USA (2008), investigated the contribution of aerial plant parts versus the root zone for the removal of gaseous formaldehyde. Two potted plant species (Fatsia japonica and Ficus benjamina) were assessed and compared for both day and night-time function.

The plants were placed in airtight chambers (1.0 m³) and exposure to formaldehyde concentration of (2 µLL¯¹).The removal capacity of the relevant plant parts (complete, aerial parts and root zone) were determined by the time interval taken to reach 50% of the initial concentration.

The researchers found, that for both species:

• There was an initial rapid removal rate which decreased as the chamber concentration diminished
• That the aerial plant parts reduced concentration levels during the daytime, but were of limited use at night
• That the plant root zone parts reduced concentration levels both during day and night-time function

It was also determined, that:

• the ratio of formaldehyde removal by aerial plant parts versus the root zone was found to be 1:1 during the day and 1:11 at night

The researchers conclude that the effectiveness of the root zone was largely due to microorganisms and roots (90%) and only about (10%) due to adsorption by the growing medium.