damp

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damp,

in mining, any mixture of gases in an underground mine, especially oxygen-deficient or noxious gases. The term damp probably is derived from the German dampf, meaning fog or vapor. Several distinct types of damp are recognized. Firedamp is methanemethane
, CH4, colorless, odorless, gaseous saturated hydrocarbon; the simplest alkane. It is less dense than air, melts at −184°C;, and boils at −161.4°C;. It is combustible and can form explosive mixtures with air.
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 and other flammable gases, often mixed with air; it results from the decomposition of coal or other carbonaceous materials. Explosive mixtures of firedamp with air usually contain from 1% to 14% methane. The mixture of gases that remains after a firedamp explosion is called afterdamp; it consists chiefly of carbon dioxide and nitrogen. Chokedamp is any mixture of oxygen-deficient mine gases that causes suffocation. (In England, carbon dioxide is called chokedamp.) Several methods are used for detection of damps. The Davy safety lampsafety lamp,
oil lamp designed for safe use in mines and other places where flammable gases such as firedamp (see damp) may be present. Its invention (c.1816) is usually attributed to Sir Humphry Davy.
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 is one of the earliest detection devices. The color and height of the lamp flame indicate the amount of firedamp present; if the flame is extinguished, chokedamp is present. Canaries were formerly kept in mines; the birds are overcome by relatively small quantities of noxious gases, and their death warned the miners of the presence of damps. Special colorimetric detectors are now used. The methanometer is a special portable instrument used to detect firedamp.
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damp

[damp]
(engineering)
To reduce the fire in a boiler or a furnace by putting a layer of damp coals or ashes on the fire bed.
(mining engineering)
A poisonous gas in a coal mine.
(physics)
To gradually diminish the amplitude of a vibration or oscillation.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Green netting is also useful, but there is no substitute for damping down.
Firefighters asked power engineers to isolate the electricity supply before they could complete damping down operations at the scene.
A North Wales Fire and Rescue Service spokeswoman said: "Firefighters were at a farm on Wrexham Road, Wrexham throughout the night damping down yesterday afternoon's barn fire.
"The fire was under control by 1.51am the next morning but firefighters were in attendance damping down until 4.30pm.
Cheshire fire and rescue managed to put out the fire, but were still on the scene "damping down" later yesterday to make sure the fire was fully out.
Firefighters from Dewsbury spent about half an hour putting it out and damping down.
This morning fire crews were still damping down the charred remains of the site, known at Pelaw Court.
Warwickshire Fire and Rescue Services Incident Commander Ian Tonner said last night: ''Crews remain on site damping down and are expecting to be on-site throughout tonight."
The blaze was brought under control within an hour and two crews from Highgate and Binley remained at the scene damping down.
Crews were at the scene throughout the night and early today one crew continued damping down.
Firefighters were damping down until 2.35am and returned in daylight today to check the site was safe.