Background Information:
Mine Ventilation Miners working underground need a constant supply of fresh air. This is important for stopping build up of gases such as carbon dioxide and methane. Good ventilation can also dilute dust in the air in underground workings, and will help cool down workers and machinery. Air needs to be drawn or forced around all the areas where men are working. Within mines the roadway system is designed so that some carry fresh air into the workings, and others carry stale air back to the surface. Air-doors are used to move the air through the workings. Even on the underground tour at the Museum, it is essential to keep air doors tightly closed.
A simple mine ventilation diagram from an NCB training booklet. Š Queen's Printer and Controller of HMSO, 2013
There are usually two shafts at mines: the downcast is where fresh air comes into the mine, and the upcast takes the stale air away. In modern times, fans are usually used to draw (suck) air through the upcast shaft from the working coal faces, where in turn it is pulled from the downcast shaft. Some mines can use a fan to force (blow) air into the downcast shaft around the workings and out of the upcast.
In the past, fire or a furnace might be used at the bottom of the upcast shaft. The heat would draw clean fresh air through the mine, using air-doors to direct the flow of air to the parts of the mine that needed it, and the smoke and fumes would go up through the shaft. This type of shaft was known as a furnace shaft. These furnaces could be dangerous due to some of the gases produced by mining. By the mid-1800s steam-powered fans and by the 1900s electric replaced the furnace. The fan was situated on the surface, and linked to the shaft, to either pull or force air through the workings. Air-doors are still required underground, to direct the air to those parts of the mine that need it.
An air-door in use in an early mine. Š NCM M E
As air is moved around the mine workings, it gathers heat. The heat comes from the men and machines at work, and the depth of the workings. Miners found that working nearer to the downcast shaft the air would be cool, but working nearer to the upcast shaft the air would be hotter and dustier.
Industrial Training Branch of the National Coal Board, 1981. Pit Ventilation (NCB).
Find out more about ventilation, on site at the Museum in the Coal Interface Gallery and on the underground tour.