A ventilation shaft is an open passageway designed to allow air circulation to or from an enclosed space. These shafts are common design and construction elements in subterranean projects of all kinds, including subways, service tunnels, living spaces, and mines. They may bring fresh air to a space, or remove stale or polluted air and often have fans or heating and cooling machinery integrated with their ventilation functions.
Man has known for centuries that fresh air is a necessity to health and well-being. Mines have long employed ventilation shafts to allow the continual circulation of air into the deepest areas, bringing fresh air to workers on the lowest levels while carrying away air that has become stale or contaminated with noxious or explosive fumes and gases. While a well-designed system of ventilation shafts may not require fans to keep air circulating, most mines with ventilation shafts are designed with large fans to help move massive amounts of air.
While mine ventilation is one of the most common uses for a ventilation shaft, they are found in all manner of settings, above and below ground. Any underground installation will require ventilation to keep fresh air supplied to its workers or inhabitants and to remove or allow stale air to escape. Subways, military installations, workspaces, and even museums are just a few of the subterranean constructions that require ventilation shafts.
Surface buildings often employ ventilation shafts to circulate air in otherwise enclosed spaces. Air ducts are common in nearly every modern building, and are used to circulate air as well as to bring heated or cooled air to work, living, and commercial spaces of all types. Large, complex systems of ventilation shafts, integrated with fans and heating and cooling machinery, can be found in the hidden spaces in walls and ceilings of houses, businesses, factories, and skyscrapers alike.
One type of ventilation shaft that has been around for as long as man has employed fire indoors is the chimney. These structures are the simplest form of ventilation shaft, usually a simple, vertical column used to carry smoke from a fireplace or stove up and out of a home or other building. While many ventilation shafts operate in pairs, one bringing air in and the other letting air out, chimneys are intended to carry air out, expelling smoke along with it. Air circulation is completed by air entering the building through windows, doors, and other openings.