Cynheidre-Pentremawr outburst, 1971

Shortly after noon on 6 April 1971, a heading being driven in the No. 2 Cross Measure Driveage at Cynheidre erupted without warning, ejecting around 400 tons of fine coal and roughly two million cubic feet of firedamp into the workings. Six men were killed by asphyxiation, and the gas travelled far enough through the ventilation system to overcome dozens more at a longwall face a considerable distance away before a quick-thinking electrician shut down an auxiliary fan and slowed its spread.

Cause

A spontaneous outburst of coal and firedamp from geologically disturbed ground during heading drivage.

Contributing factors

An independent analysis by researcher Phil Cullen identified several breaches of the 1958 Outburst Code: the affected coalface had lost dedicated unit ventilation once cross-cut development began; the development heading lacked airline breathing sets or self-contained breathing apparatus; the heading was driven from the intake rather than the return side of the ventilation system, channelling contaminated air toward working areas rather than away from them; and the colliery's own Outburst Committee had not enforced code compliance despite airline breathing systems being available and already in successful use at Yorkshire collieries.

What happened

The men in the heading had spent the morning filling sandbags with unusually dusty, friable coal after an inspection had found the ground unstable; the mechanical shovel loader was left unused as a precaution. At around 12:15pm the seam erupted, ejecting some 400 tons of coal and roughly two million cubic feet of firedamp within the first seven hours of measurement. Three men working in the heading itself tried to escape but were overcome by the gas and dust before they could get clear. The methane then travelled through the ventilation system to Panel 13, a 130-yard longwall face where about 25 men were working; several lost consciousness before waking disoriented, and undermanager Philip K. Lewis tried to warn men to keep their heads low toward cleaner air near the ground before he too was overcome. An electrician, Gordon Rowlands, shut down an auxiliary fan that was drawing the gas toward the working face, almost certainly preventing further deaths.

Rescue & recovery

The acting colliery manager raised the alarm at 12:26pm; the Loughor Mines Rescue Station team arrived within 24 minutes, and teams from Loughor, Dinas, Porth, and later Brynmenyn and Bridgend, took part in the operation using breathing apparatus. All survivors had been brought out by 2:15pm; recovery of the dead continued until 3:40pm. Sixty-nine other men suffered reportable injuries and were treated across three local hospitals.

Investigation & inquiry

HM Inspector of Mines J. S. Marshall led the official inquiry, which concluded the disaster arose from spontaneous outburst conditions in geologically disturbed ground and recommended improved ventilation layouts to direct outburst gas away from working areas, mandatory advance boring and coal-desorption testing ahead of all headings, breathing apparatus for heading workers, and independently powered loudspeaker communication throughout the workings.

Changes to practice & legislation

The disaster led the national Outburst Code to be substantially revised in 1974, adding mandatory unit ventilation for all longwall faces, rules preventing heading return air from reaching other working areas, installation of airline breathing stations, and escape breathing apparatus for all heading workers. A further 29 outbursts occurred at Cynheidre before its 1989 closure, 17 of them spontaneous, but none caused further deaths.

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• A spontaneous outburst in the No. 2 Cross Measure Driveage at around 12:15pm on 6 April 1971 ejected some 400 tons of coal and about two million cubic feet of firedamp. ¹
• Six men were killed by asphyxiation: Douglas Lyndon Davies, William Luther Davies, Henryk Itzi, Albert Miller, Henry Garfield Roberts and Gareth Watkins (sources give his age as either 54 or 43; not resolved in this pass). ^1,2
• An independent analysis found the colliery had breached several provisions of the 1958 Outburst Code, including inadequate unit ventilation and the absence of airline breathing sets in the heading. ¹
• Electrician Gordon Rowlands shut down an auxiliary fan that was carrying gas toward a working longwall face, an action credited with preventing further deaths among the roughly 25 men working there. ¹
• HM Inspector of Mines J. S. Marshall's inquiry led to a full revision of the national Outburst Code in 1974. ^1,2

Related terminology

Mining terms this disaster is structurally linked to, with the nature of the relationship.

• Breathing Apparatus (contextual relationship)
  Automatically linked by scripts/link_terms.py: exact-phrase match in the record's own recorded text.
• Coal (contextual relationship)
  Automatically linked by scripts/link_terms.py: exact-phrase match in the record's own recorded text.
• Firedamp (direct cause)
  The methane released in the outburst, which travelled through the ventilation system to overcome men working elsewhere in the mine.
• Longwall (contextual relationship)
  Automatically linked by scripts/link_terms.py: exact-phrase match in the record's own recorded text.
• Mines Rescue Station (contextual relationship)
  Automatically linked by scripts/link_terms.py: exact-phrase match in the record's own recorded text.

Sources

1. (primary) Cynheidre Colliery — welshcoalmines.co.uk
2. (primary) Cynheidre-Pentremawr Outburst, Llanelli, 1971 — Northern Mine Research Society

Record created: 24 August 2026 · Last researched: 24 August 2026