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.

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.
References in periodicals archive ?
Often rubble and arisings - bits and bobs left behind by the builder or previous owner - are deposited under the floors as a convenient means of disposal and such blockages are commonly found to be a cause of transferring dampness to flooring and walls at low level.
Dry rot just loves the warm weather, heavy rain causing intermittent dampness rather than saturation and a humid atmosphere.
Some causes of dampness can be obvious, the leaking gutter or hole in the roof doesn''t require the building pathologist to pontificate on the source.
The room must be capable of keeping the weather out and that includes dampness from the ground.
The difficulty with resolving dampness problems isn't just finding out where it's come from, although without that you don't have much hope of stopping it, but we need to know the intensity and how long the dampness has been going on.
But when the stack is at the side of the house, poking out of the eaves rather than the ridge, there is minimal or no roof void, so the dampness will readily soak down and show up in the bedroom.
Rising dampness will have various dissolved nitrates, chlorides and other natural salts found in the ground (called hygroscopic ground salts) which will be carried upwards into the brickwork and plaster.
South Tyneside Homes said: "Miss MacDonald reported dampness in her bathroom and bedrooms.
Even if the temperature isn't freezing, a layering of waterproof, breathable clothing prevents dampness from seeping through to the skin.
The tubers need to be stored in a cool yet frost-free place with good air circulation and no risk of dampness - a cardboard box full of shredded paper is perfect
You can check for dampness around this area and on the carpet.