Smoke clouds

The life persistency of a smoke cloud is deterrnined chiefly by wind and convection currents in the air. Ambient temperature also plays a part in the continuance or disappearance of fog oil smokes. Water vapor in the air has an important role in the formation of most chemically generated smokes, and high relative humidity improves the performance of these smokes. The water vapor not only exerts effects through hydrolysis, but it also assists the growth of hygroscopic (deliquescent) smoke particles to an effective size by a process of hydration. Smoke may be generated by mechanical, thermal, or chemical means, or by a combination of these processes (7). 

Scbwaden, m. noxious vapor or exhalation, damp specif., choke damp gas cloud smoke cloud swath. — feurlger —, fire damp. 

In Britain, Leblanc pollution went uncontrolled for decades. A visitor outside Liverpool, a major Leblanc factory center, described in 1846 a sordid ugly town. The sky is a low-hanging roof of smeary smoke. The atmosphere is a blend of railway tunnel, hospital ward, gas works and open sewer. The features of the place are chimneys, furnaces, steam jets, smoke clouds and coal mines. The products are pills, coal, glass, chemicals, cripples, millionaires and paupers. An estimated 40,000 men, women, and children— many of them Irish escaping the potato famine—worked in British Leblanc factories. Until 1875, workers stirred batches of chemicals in a cloud of hydrochloric acid gas. Their teeth decayed, and their clothing burned. Inhaling deeply could make them faint and vomit. 

Once the fire characteristics are calculated, an assessment of the impact of the fire needs to be completed. Fires produce four major outputs gases, flame, heat, and smoke. The materials involved in the fire will determine the combination of these four outputs. For example, crude oil will produce a very dark thick smoke cloud, and ethylene does not produce much smoke, but does have a very large flame. 

One of the major applicahons of pyrolants is to produce smoke clouds or smoke curtains by chemical reactions.I -s] Smoke is defined as condensed particles that can remain in the atmosphere for at least several seconds. The radiative emission from smoke itself is small because of its low-temperature nature. Thus, no visible emission is seen in the dark by the human eye. The applications of smoke are ... 

For coloured smoke puffs, pigments based on metal chromates are utilised, the pigment being intimately mixed with a fuel such as magnesium. On combustion in free air, a smoke cloud is produced that has residual colour due to the chromate. 

Although blue dyes usually appear to be blue-black in bulk, a blue colour is seen when they are viewed at the edge of a smoke cloud. This is related to the spectral characteristics, concentration and particle size of the dye. 

Volatilization of oil A pyrotechnic reaction produces the heat needed to vaporize high molecular weight hydrocarbons. The subsequent condensation of this oil in air creates a white smoke cloud. The toxicity of this smoke is probably the least of all the materials discussed here. 

Two basic processes are used to create smoke clouds the condensation of vaporized material and the dispersion of solid or liquid particles. Materials can either be released slowly via a pyrotechnic reaction or they can instantaneously be scattered using an explosive material. Technically, a dispersion of fine solid particles in air is termed a smoke, while liquid particles in air create a fog. A smoke is created by particles in the 10 -10 " meter range, while larger suspended particles create a dust (1). ... 

Wrap a coil of Primacord explosive, sometimes covered with black grease, around the camera observation port window safety glass outside the instrument shelter. Detonation of the explosive coil creates a dense black smoke cloud. This method is usually called a smoke shutter... 

Grenade, Rifle, Smoke, M22A2 Rifle Launcher Green Smoke Cloud on Impact 8 600 10.14 1-88 16... 

Grenade, Hand, Smoke, HC, AN-M8 Hand-Thrown White Smoke Cloud 105 4.5 2.6 23... 

The acids formed are hygroscopic and absorb moisture from the atmosphere to produce submicron-sized droplets of an aqueous solution of phosphoric acid and a series of polyphosphoric acids. It is the mist of these acids which constitutes the white smoke cloud and scatters visible and near-IR electromagnetic radiation. The amount of smoke formed depends on the RH of the atmosphere. Under high humidity conditions, it is possible to achieve yield factors of four or even higher. 

Transmission through a smoke cloud at wavelength A. and is equal to the ratio of final intensity of radiation (I) and initial intensity of radiation (f0), that is (1/10). 

The screening efficiency of a smoke cloud is generally measured in a smoke chamber. 

Smoke shells and rockets are used to produce smoke clouds for military signaling and, in daylight fireworks, for ornamental effects. The shell case or rocket head is filled with a fine powder of the desired color, which powdered material need not necessarily be one which will tolerate heat, and this is dispersed in the form of a colored cloud by the explosion of a small bag of gunpowder placed as near to its center as may be. Artificial vermilion (red), ultramarine (blue), Paris green, chrome yellow, chalk, and ivory black are among the materials which have been used, but almost any material which has a bright color when powdered and which does not cake together may be employed. 

Because smoke clouds may be regarded as arising from point or line sources, we shall begin this chapter with a treatment of them. Dust and sand storms are more complicated phenomena arising from areal sources. The former are, in a sense, limiting cases of the latter, although we cannot generalize as yet. There are certain important physical differences, which will be indicated as the subject matter develops. 

---