Production of test gases in the ppb range for round-robin tests and quality assurance measures during the measurement of VOCs
Workers exposed to volatile organic compounds (VOCs) very often suffer damage to health, and VOC odours may also represent a serious nuisance. The compounds concerned may be numerous and highly diverse; the concentrations of the individual substances however are generally relatively low. Quality assurance measures such as round-robin tests for the measurement of VOCs in indoor areas or at workplaces have not so far been available. A particular reason for this is the challenge presented by the production of test gases in the necessary concentrations. The BGIA test gas facility has therefore been modified for the production of test gases in the µg/m3 range. A two-stage primary gas purifier, a continuous test gas generator with multi-stage dilution, a capillary evaporator for low-volatility compounds and an online thermodesorber have been installed specifically for this purpose.
Since 2007, the BGIA has been offering round-robin tests for VOCs with local sampling in the range from 5 to 50 µg/m3. The first round-robin tests show that good results are obtained at concentrations from 10 to 50 µg/m3. At the lower concentration of < 15 µg/m3, however, the number of participants experiencing deviations from the reference value was substantially higher. The round-robin tests also involved the taking of blank readings prior to the start of test gas dosing. Some two-thirds of participants were unable to detect any interfering components; the remaining participants produced blank readings the levels of which could not always be explained. The problem may be caused in this case by the carrier material Tenax TA which is usually employed.