Nitrous fume concentrations during shotfiring in coalmines

A short sampling trial has been carried out at five British coalmines to assess both the short term and shift average exposure of men to nitrous fumes (nitric oxide and nitrogen dioxide) during shotfiring. Eight shotfiring shifts were sampled with Drager detector tubes at a variety of work places, including coalfaces, return road and headings, so as to avoid undue bias. Other measurements were taken with the driver of a diesel locomotive, for comparison. The results are summarised in this report. The results of similar short period investigations by Scientific Control are also reviewed. Alternative sampling methods and difficulties are discussed and recommendations are made for further work.The work confirms that nitric oxide is the major compoment of nitrous fume in coalmines. The shift average exposure to all forms of nitrous fume were low: less than circa 4 ppm for nitric oxide compared with the threshold limit value of 25 ppm recommended by the American Conference of Governmental Industrial Hygienists (ACGIH, 1971), and less than 0.3 ppm for nitrogen dioxide. High peak concentrations occurred directly after shotfiring but diminished fairly rapidly, especially in the case of nitrogen dioxide. The ACGIH ‘coiling value’ of 5 ppm for nitrogen dioxide was momentarily exceeded on two shifts. These results are in broad agreement with Scientific Control’s findings and are probably typical of conditions in British coalmines.In the absence of evidence on the nodical effects of long term exposures to low concentrations of nitrous fumes, it is proposed that a limited survey should be started at four collieries to establish whether shotfirers are in fact exposed to higher lovels of these gases than other typical face or elsewhere underground groups. This work night usefully be linked to current nodical and statistical studios of lung function among shotfirers.A much longer and, perhaps, continuous study will be needed to evaluate tho long torn exposure of all men exposed to nitrous fune at the selected collieries. A project of this nature in parallel with medical studies would bo expensive in manpower and materials; especially if an attempt was nado to assess possible synergistic effects due to dust, carbon monoxide or gases adsorbed on dust. It would be premature to recommend such a scheme at this stage but some work on the development of alternative sampling methods would be prudent.Detector tubes provide a relatively expensive method of sampling whole shift exposures and also require continuous supervision. Significant, economies would be achieved if shift average exposures to nitrous fucie could be measured by adapting the MEE or personal gravimetric dust sampler to draw filtered air continuously, or interrittcntly, through one or more detector tubes, or through a reactive paper, either following the dust filter or alone. It is proposed that the technical problems should be investigated. This will not assist tho measurement of peak concentrations, should this still be considered necessary. “”