At two collieries using American mining techniques members of the union are unable to fulfill their statutory duty of testing for gas at coal faces, the union alleges.
The two pits concerned, Asfordby in Leicestershire and Point of Ayr in North Wales, use the 'deep cut' procedure whereby digging machinery bores further into the seam before supports are put in place. That means that colliery deputies are unable to enter the newly exposed area for fear of roof collapse. Monitoring equipment used by the deputies cannot reach all areas of the face to test for gases, it is alleged.
Management acknowledged yesterday that the law specified distances for roof supports as faces advanced, but British Coal had legitimately applied for exemptions at the two pits.
Peter McNestry, leader of Nacods, argues that Boyd's, the US company presently testing the feasibility of collieries under threat of closure, is keen to promote the system.
Mr McNestry believes that the Government and British Coal also want to see the method extended so that productivity would be higher under privatisation.
The Health and Safety Commission has suspended its judgement on the issue until after the Department of Trade and Industry produces its White Paper on the future of the industry.
Nacods believes that while the system may be more appropriate in the United States, where mines are shallower and gas less prevalent, the procedure could lead to more fatalities and injuries if used extensively in this country. Even in the US, nearly half the roof falls happened at extended cut collieries, which only account for 18 per cent of total mining capacity, according to figures from the United Mineworkers of America. The US deep cut pits also accounted for 63 per cent of 'ignitions' due to methane.
In most British pits supports are set up every 2 metres as the face machinery cuts into the seam. The US method allows cuts of 6.6 metres or even 9 metres.
Mr McNestry believes that when the costs associated with accidents are taken into account, there would be little to choose between the two methods.
He argues that under the new Clinton administration there is likely to be an inquiry into the safety of the procedures. 'We could be introducing a US method at a time when the Americans are abandoning it,' he said.
'Why have we got to accept a system of mining that is clearly unsafe? People are being told: accept this system or you're out of work.'
A spokesman for British Coal said it was not unusual for managers to apply for exemption from the law when they were testing a new production method. The deep cut procedure was just one system under evaluation to increase productivity.
'The mines inspectorate would not grant us exemption unless they were satisfied it did not compromise safety. We can't just barge in willy nilly. In any case it's been proved that the most productive pits are the safest,' he said.