ABSTRACT
Portable workplace multi-gas monitors are used by the construction industry during compressed and free air tunnelling. This paper details a study of the effects of constant and transient pressure on the performance of two commercially available portable multi-gas monitors, and on the sensors used in these monitors. The monitors were subjected to gradually increasing and constant pressure (0 - 3.5 bar-gauge) and to pressure pulses up to 0.3 bar. Both types of monitor are affected by pressure and the reasons for this are discussed. Calibration of the monitors at the working pressure, under constant pressure, returns their performance to within specification. Transient pressure changes always affect the performance of the monitor, particularly the oxygen response, increasing the risk of false alarms. The merits of measuring volume fraction over partial pressure oxygen concentration in the workplace are argued. Finally, guidance is provided in the form of a limited number of recommendations on the use of portable gas monitoring equipment in hyperbaric atmospheres.
