Figure 1. Spatial ventilation plan of a district in the safety pillar for the town of Bytom—level 660 m

On 30th October in the colliery M about 110 dm3 of the SF6 tracer gas were injected into a suction hole drilled into a gob part of the seam 418 on the 500-m level (the gate road adjacent to the gob of the longwall 304). The pertinent gob portion of the seam 418 (i.e. caving-gobs of the longwalls 304 and 305) in the colliery M is located right at the boundary between the lease areas of the collieries M and W.