Carbonaceous Aerosol Speciation System Model CASS

The Magee Scientific Carbonaceous Aerosol Speciation System CASS operates and simultaneously controls an operation of 2 instruments, i.e., the Total Carbon Analyzer TCA08 and the Aethalometer AE33. The first one collects a sample of atmospheric aerosols on a quartz fiber filter positioned inside a small stainless-steel chamber at a controlled sampling flow rate of 16.7 LPM. The default sampling time of TCA08 is 60 min but can be set from 20 min – 24 h, depending on the ambient aerosol concentrations. TCA08 instrument consists of 2 identical parallel channels, in which ball valves and solenoids are controlling air-flows. A continuous operation is enabled and sustained by the following principle of operation: while one channel collects its sample, the other channel analyzes an already collected one and reports a Total Carbon TC level on a set time-base (from 20 min – 24h). After collecting the filter, two flash-heating elements combust the sample instantaneously in a small ‘analytic’ flow of filtered ambient air. This converts all the carbonaceous compounds into CO2and creates a short, but large-amplitude pulse of CO2 in the analytic flow passed to the NDIR CO2 detector. The background level of CO2 in ambient air during the heating cycle is determined before, and after the heating cycle, the provide the baselines against which the combustion pulse is measured. The CO2 concentration over the baseline is integrated to give the sample’s Total Carbon (TC) content.