A chimney is a structure, usually made from brick, which removes unwanted gasses and smoke from appliances such as fireplaces, boilers, and stoves, and carries them outside. The chimney is usually made from brick, and is vertical to ensure that harmful gasses, such as carbon monoxide, are drawn out efficiently into the open air.
One reason why chimneys are so tall is to increase the draw of air, thus allowing the adequate dispersion of gasses before they are released out of the chimney and into the atmosphere. The ‘stack’ or ‘chimney’ effect refers to the movement of air within and outside of structures, and this effect is driven by temperature and moisture differences – the greater the height of a structure, the more efficient the chimney/stack effect, ensuring excellent ventilation. The inside of the chimney is known as the flue, and chimney pots considerably lengthen the flue in order to improve draught.
Other components of the chimney include chimney cowls, which help to prevent backdraught (where wind blows smoke and potentially harmful gasses back into a room). The chimney cowl works by rotating and aligning itself with the blowing wind.
Caps (known as chimney caps) may be placed on chimney pots to prevent birds, squirrels, and other small mammals from gaining access to the chimney and nesting there, causing a potential blockage. Some chimney caps have a rain guard on to prevent rain from entering the chimney, and others have wire mesh attached, to stop any burning embers or debris escaping onto the roof and posing a fire risk.
Chimneys have been around since the 12th century, and industrial chimneys appeared in the 18th century as a consequence of the industrial revolution. Early chimneys were very basic, but their modern counterparts were much more sturdily constructed from brick and featured chimneypots to control downdraught. Today, many chimneys are redundant – many modern gas appliances come with gas vent pipes, which are simply fixed to an outside wall.
Industrial chimneys are different from a regular chimney, in that they are completely external from a commercial building. Usually placed near a boiler or furnace, noxious gasses are carried to the chimney by ductwork.
