brattice

A brattice is a temporary or semi-permanent barrier built inside a mine to control the flow of ventilation air. In coal mines especially, it divides the passage of underground roads and chambers so that fresh air from the shaft can be forced down one path and return air (laden with gas, dust, and heat) back up another, without the two streams mixing. Without brattices, air would take the easiest route and leave large sections of the mine dangerously unventilated.

The traditional brattice is a wooden frame lined with canvas that has been coated in tar or similar waterproof compound. The canvas is stretched tight over wooden studs, usually about 2 to 3 inches square, and secured with nails. The tar coating prevents water seeping through and extends the life of the cloth, which otherwise rots quickly in the damp underground environment. Modern brattices may use corrugated metal sheeting or plastic-coated fabric instead, but the principle remains identical: a lightweight partition that can be erected quickly and moved when mining advances into new areas.

Brattices are essential in longwall and pillar mining, where the layout of working areas changes continuously. A brattice might run the length of a roadway, or block off side passages to force air in a specific direction. Poor ventilation in a coal mine allows methane and other firedamp gases to accumulate; a properly placed brattice system, combined with forced-air ventilation fans, dilutes these gases to safe concentrations. Failure to maintain brattice integrity, through damage, deterioration, or incorrect placement, has been a factor in historical mine explosions and poisoning incidents.

Why the name persists

The word brattice comes from the Old French bretèche, a wooden structure built on castle walls. The term entered mining vocabulary centuries ago and stuck, even though the underground partition bears no relation to medieval fortifications. Its survival in the trade reflects the deep history of coal mining itself.

Installation requires careful planning by the mine ventilation officer. Air pressure, the number of workers in each section, the presence of gas-prone areas, and seasonal temperature changes all affect where and how brattices should be positioned. A brattice that works well for autumn conditions may need adjustment as winter cooling increases air density and changes flow patterns. In modern mines, ventilation plans are modeled before construction, but on-site adjustments remain common.