The effects of indoor plants in the living space and at the workplace are noticeable. Plants help to improve the indoor climate because they not only produce oxygen, but also filter pollutants from the air. These can, for example, dissolve from materials in the room, such as paint, flooring or furnishings, and are released into the air. In this way, the substances enter our lungs and can affect our health. Certain plant species are particularly helpful in absorbing, for example, benzene, formaldehyde or trichloroethylene - all chemicals that sound dangerous (and are) but are frequently found indoors. In this process, the plants absorb the toxins through their leaves, neutralise them and convert them into harmless components. In addition, plants convert the carbon dioxide (CO₂) contained in the indoor air into oxygen and biomass through photosynthesis. However, these air-improving processes come to a standstill for most plants at night. During this period, CO₂ is even emitted, which is particularly interesting when it comes to plants in bedrooms.
Houseplants as humidifiers
Plants also help to improve the humidity in living spaces. For example, they release over 90 percent of the water they water through their leaves back into the air. This is particularly beneficial to health in the winter months, as heating greatly reduces the relative humidity of the air in the room - often to less than 20 percent. However, the humidity in living rooms or offices should generally not fall below 30 percent; a relative humidity of between 40 and 60 percent is recommended (see our article on minimum humidity). Depending on the type of plant, the number of plants in the room, the size of the room and the watering intervals, this can increase the humidity by 5 to 20 percent. However, plants are also helpful in summer. This is because the temperature can be regulated through the air purification process and the supply of moisture by the plants.
air-Q Lab: How plants affect air quality
In our test, we used the air-Q to check the effects of indoor plants on the indoor air. For the test setup, we placed various green plants together with the air-Q under an airtight glass dome for 24 hours. This was to largely exclude external influences on the air. The following measured variables were then examined:
- Humidity
- Carbon dioxide
- VOC
- and the room temperature
These values were measured with the sensors in the air-Q and tracked over time. In our video you can follow our experiment in fast forward.
The test started in the afternoon around 3 pm. At the beginning, the CO₂ reading still dropped slightly in daylight, but then rose from about 750 ppm (part per million) from about 6 p.m. to 1,000 ppm by sunrise. In daylight, the CO₂ value dropped again under the glass dome and reached about 600 ppm, which can be attributed to the onset of photosynthesis by the plants during daylight.
The humidity rose steadily over the course of the test until it reached almost 100 per cent. The temperature also dropped overnight and rose again during the day - not surprisingly, as it is warmer in the office during the day.
The VOC value, on the other hand, is difficult to interpret. First it dropped slightly at night and rose again during the day for unspecific reasons - but at a very low level. One possible explanation is that the soil in the pot emits VOCs, as it is an organic product with a decomposition process going on in the background. This needs to be investigated further, e.g. by artificially adding VOCs to subsequently observe the decomposition process.
Conclusion of the study: plants are ideal humidifiers
The test thus confirmed that indoor plants basically have a positive influence on air quality. Our test plants were able to contribute to a higher air humidity. Thus, plants as natural humidifiers significantly reduce the risk of colds. Since a saturation of 100 percent was quickly reached under test conditions, it can be assumed that the effect is also measurable in the room.
It has also been proven that plants release more CO₂ when the photosynthesis process stops. Our test setup had an air volume of less than 0.1 m³. A normal room of 20 sqm, on the other hand, has an air volume of about 50 m³. This results in a factor that is more than 500 times greater. If you extrapolate the positive CO₂ balance of the plants during the day and the negative one at night, the effect is in the single-digit ppm range, even with windowsills full of plants. So you don't have to worry about running out of oxygen at night.
Further tests in our air-Q Lab are in the pipeline!
(Contributed image: Canva/KatarazynaBialasiewicz from Getty Images Pro)
