One of these ideas comes from Florafilt, an air purifier start-up from near Cottbus in the Spreewald. Founder Reinhard Mietusch and his team have developed a biological air purifier that uses plant roots to filter the air to a much greater extent than conventional alternatives that only involve the foliage. The room air is drawn into the air purifier by a small fan and actively passed over the plants' roots. The process is said to be 20 times more effective in purifying the air and filtering volatile organic compounds(VOCs) from the air we breathe. In addition, the air humidity is also said to quickly increase to a healthy level.
The starting point for functioning air purification is the reliable analysis of air quality. Therefore, we made our air-Q air measuring device available for test measurements with the latest Florafilt device "Apollo". The aim of the test was to find out how well the invention can filter a toxic VOC, such as toluene, from the air. In addition, it was also investigated how the air humidity changes in the test room at the Technical University of Dresden.
Aromatic hydrocarbon toluene
Toluene belongs to the group of aromatic hydrocarbons and thus falls into the category of VOCs. Other common names for the chemical are retinaphtha, methylbenzene and phenylmethane. Toluene is mainly used as a solvent in paints, varnishes, printing inks and adhesives.
Toluene is a colourless, characteristically smelling and volatile liquid. It burns with a strongly luminous and sooty flame and forms not only highly flammable but even explosive vapour-air mixtures. The flash point is 6°C - this characteristic property is also used in the production of the explosive TNT. Both petrol and petroleum contain toluene. In addition, it can be formed in incomplete combustion processes, such as smoking cigarettes.
Inhalation of toluene vapours can cause considerable damage to health. In addition to irritation of the eyes and respiratory tract and the risk of allergic reactions, unspecific symptoms such as fatigue, malaise and disturbances of sensation and coordination of movement, even unconsciousness, can occur. Toluene also causes nerve damage and attacks the kidneys and liver. It is considered dangerous for reproduction and can even be fatal in larger quantities.
The narcotic effect of toluene can produce states of exhilaration and excitement. Regular contact can be addictive.
Limit values were introduced to reduce the risk from toluene. The European Union agreed on an eight-hour average value of 192 milligrams per cubic metre (mg/m³) or 50 parts per million (ppm) and a short-term limit value of 384 mg/m³ or 100 ppm.
The MAK Commission recommends a maximum workplace concentration (MAK) of 50 ml/m³ or 190 mg/m³.
Air purifier measurement at the TU Dresden
During the four-day test at the TU Dresden, the developers from Florafilt investigated with their air purifier "Apollo" whether the toluene concentration in a closed room can be significantly reduced.
For this purpose, the air quality in the approximately seven-square-metre test room was first monitored over a day to detect periodic effects. Then the gas toluene was introduced into the room in a controlled manner.
On the first of the total of four test days, it was checked to what extent this concentration drops due to the plants in the room but without the help of the air purifier "Apollo". No decrease in the toluene level could be measured.
The following day, the experiment was repeated, this time with the biological air purifier in operation. The curve recorded by the air-Q clearly shows that "Apollo" lowered the VOC value considerably faster and more strongly. At the same time, the plants in the room increased the humidity.
It was particularly exciting for us that Florafilt used both our air-Q and a special measuring device for toluene only from Dräger (type X-am 8000) for the tests. In terms of the quality of the measurement results, the air-Q was able to keep up well with the very expensive special device. For example, the air-Q measures to the second. And the VOC sensor in the air-Q, which we specially selected, reacted very well and strongly to the dangerous toluene. This can be clearly seen on the measurement curve of our air-Q by the sudden increase in the VOC concentration.
The air-Q also has several advantages in terms of measurement and evaluation. For example, the air-Q monitored other parameters in parallel and correlated them with each other. One result: the positive effects of the "Apollo" on relative and absolute humidity could be proven.
In addition, Florafilt could be sure that there were no other interfering pollutants in the test chamber. In the end, our sniffer air-Q thus made a decisive contribution to precise and satisfactory test measurements of the "Apollo".
(Cover picture: Florafilt)
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