Evaluation of diffusive samplers for monitoring toxic gases and vapours in coalmines. Final report on CEC Contract 7260/04/08

Diesel engines, resins and cleaning agents, which can all give off hazardous gases and vapours, are being used increasingly in British coalmines. With the increasing awareness of the potential risks to health associated with these materials it may, therefore, be necessary to monitor a wide range of gases and vapours in coalmines in the future, There are many procedures capable of sampling and analysing toxic gases and vapours in coalmines. Diffusive (or passive) samplers are particularly attractive because of their size and simplicity (no electrical pump is needed), ease of use and low cost. However, validation studies of these devices have not covered the relatively harsh environmental conditions encountered in coalmines and there is a dearth of information on their performances at high windspeeds, in turbulent air and in dusty atmospheres.The aim of this study was to investigate whether diffusive sampling offered a practical solution to sampling toxic gases and vapours in coalmines by studying the performances of a range of diffusive samplers under such conditions.A series of laboratory tests were, therefore, carried out in wind tunnels to determine the effects of windspeed, sampler orientation, turbulence, fluctuating vapour concentrations and dust on the performances of six commercially available diffusive samplers (SKC 530, 3M 3500, Drager ORSA 5, Dupont Protec G-BB, MSA OVD and Perkin Elmer ATD50). A limited underground field exercise was also undertaken to validate the laboratory work.The results of the research have clearly demonstrated that diffusive sampling could be used successfully to monitor toxic gases and vapours in the harsh environmental conditions which prevail in coalmines and that diffusive samplers are potentially flexible, simple and cheap tools for this purpose. There are difficulties. In tests with only two vapours, just one sampler of the six tested (the 3M 3500) performed to its specification. (This device, we believe, is the most suitable for coalmine use). One did not perform as a static sampler in harsh conditions, two required recalibration and two were unsatisfactory. It is therefore essential that, before a diffusive sampler is used to measure any gas or vapour, independent validation data are obtained.