Calibration of the Hund tyndallometer for measuring environmental tobacco smoke in a test duct

The Hund tyndallometer (Type TM Digital μP) has recently been used to study the air quality in SAS aircraft. This publication contains an evaluation of its performance in measuring environmental tobacco smoke (ETS), comparing its output with the gravimetric method which was used for measuring respirable dust concentration (van der Wal 1988). The influence of several parameters, such as the age of ETS, the type of smoke (main stream or side stream), and the relative humidity was investigated. The Hund measurements of ETS generated by a smoking machine (ISO 7210) in a test duct were calibrated against gravimetric measurements of respirable dust trapped on teflon membrane filters. An accurate calibration was, however, not possible for outputs of less than 1 mV. This is 0.1% of the electrical output range (1 V) and corresponds to 100μg/m3 of respirable dust. For times of up to 7 min and relative humidity (RH) levels between 8 and 72%, the ageing of ETS did not appear to influence the output of the Hund. RH levels in this range also did not clearly influence the instrument response factors. Higher RH levels did, however, affect the response factor, probably due to condensation of water vapour on the particles. The average response factors for three types of cigarettes were respectively 177, 173, and 138 mg m-3 V-1. The average response factor of the Hund for measurements taken during SAS flights was 131mg m-3 V-1, with a relative standard deviation of 24%. As some of the measurements did not meet the Hund preconditions (output <1mV, gravimetric concentration <100 μg m-3), they were excluded from this evaluation. The Hund tyndallometer can be a useful instrument to collect additional information on real-time peak concentrations under limiting operating conditions.