Measurement of ultrafine particles with a condensation particle counter (CPC) commonly requires the use of butanol as working liquid. In laboratories the butanol vapor is generally released into the atmosphere as an environmental pollutant or it is released into the laboratory, where it is a health hazard.
Environmental agencies measure ultrafine particles especially in areas with heavy traffic. Ethene is commonly used as tracer for traffic and is monitored by the ambient air stations. The instrument used to measure the concentration of Ethene in the range of ppm is highly cross-sensitive to butanol. Hence no butanol vapor can be present when measuring Ethane. In order to remove 99.99% of the butanol vapour emitted by CPCs, a catalytic vapor filter is the method of choice. The catalytic vapor filter oxidizes the butanol vapor to CO₂ and H₂O and effectively removes the butanol, making accurate measurements of Ethene possible.
The Figure below shows an ambient air station maintained by the SMUL SACHSEN where ethene is monitored as well as ultrafine particles with condensation particle counter using butanol as working liquid.