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This chapter focuses on smoke as it relates to escape from underground mine fires. Among the topics discussed are the measurement of visibility in smoke; smoke-related hazards such as the production of CO, hydrochloric acid (HCI), or other byproducts of combustion; and miners' personal experiences while escaping through smoke. Smoke Measurement and Visibility In general, smoke consists of hundreds of thousands of very small particles. These particles have some "size," usually expressed in terms of their diameters, and they have some concentrations, usually expressed either in the number of these particles per unit volume or the total mass of the particles per unit volume. Humans cannot see individual smoke particles because they are too small. Similarly, "umber concentrations" and "mass concentrations" of smoke particles do not have much meaning to people unless they are trained technically. Still, individuals know that they can see smoke, independent of all the technical jargon used to describe it. Also, they know that when the smoke level gets too high, it is no longer visible. In fact, nothing is visible because the smoke absorbs all of the light in its surroundings. The eye is only sensitive to light in the wavelength region from about 400 nm to about 700 nm. The maximum sensitivity of the human eye is to light that has a wavelength of about 555 nm. It is important to know how the eye responds to light because if its response is known, it is possible to use a light detector that has almost the same response as the eye. Such a detector can then be used to quantify the visible characteristics of smoke because it responds in the same manner as the human eye. Smoke is visible because it either scatters or attenuates (diminishes) light. In some instances, smoke is visible because the smoke particles reflect light which is then detected by the eye. The eye actually "sees" an intensity of light that has been reflected from a cloud of smoke particles. Imagine shining a flashlight into a cloud of smoke. Someone off to the side can actually "see" the beam of light as it traverses the smoke cloud. This is called scattering. Smoke is also visible be¬cause it attenuates light. Imagine having someone shine a flashlight into your eyes. As smoke begins to build up along the beam of the flashlight, the light begins to dim. The smoke is visible because it is now reducing the intensity of light that falls upon the eye. As the smoke level increases, it is said to obscure our visibility. When the beam is no longer visible, the smoke obscuration is said to be 100%. In other words, none of the light energy from the flashlight makes its way through the cloud of smoke. Another way of saying that the obscuration is 100% is to say that the transmission of light through the cloud is zero.

Jan 1, 2000

By M. Townsend, E. L. Petsonk, H. Abrons, E. Daniloff, K. Kinsley

Workers exposed to certain inhaled dusts may show increased levels of nonspecific airways responsiveness (AR). In some studies, cigarette smokers have also been reported to have increased levels of AR. As part of an ongoing study, we compared the results of preshift methacholine inhalation challenge, spirometry, and smoking and occupational histories, in 191 under-ground bituminous coal miners (M) and 215 non-mining control workers· (C) . All M and c were selected to have normal baseline% predicted FEVI (PPFEV). Mining tenure was recorded as years worked underground (YRUG) and at the coal face (YRFC). AR was assessed as the% decrease in FEVI from baseline divided by the dose of methacholine delivered. M reported similar years smoked (YRSM) but fewer pack-years* (PY) than c~ Overall, both increasing YRSM and PY were associated with more AR*. Smoking C* but not M showed increased AR with increasing PY. In smoking and nonsmoking M, baseline AR and PPFEV showed no association with YRUG. The level of AR was inversely related to YRFC*, possibly representing selection away from dustier jobs. AR was inversely correlated with PPFEV*. In this study, AR and baseline PPFEV were not significantly associated with mining tenure, but cigarette smoking was related to both baseline lung function and level of AR. * p < 0.05 (Supported in part by Grant Gll35142, us Bureau of Mines, Generic Mineral Technology Center for Respirable Dust.)

Jan 1, 1989

By D. Harrington

"Since its establishment in 1910 the Bureau of Mines has consistently recommended the rock-dusting of bituminous and lignitic coal mines as a preventive of widespread explosions. As with many other proposed innovations, the response to the bureau's recommendation has been slow; but during the past 10 years many coal mines have done some rock-dusting, even though probably fewer than 50 of the country's approximately 6,000 coal mines are thoroughly rock-dusted. Notwithstanding the inadequacy of the rock-dusting which has been done in most of the mines which have adopted the new system, numerous cases are at hand. indicating the well-founded basis of the bureau's claims regarding the effectiveness of rock-dust in stopping explosions. Very brief descriptions will be given of several cases in which explosions in coal mines of the United States are fairly definitely known to have been stopped by rock-dust during the past 5 or 6 years; in addition, several cases are cited in which explosions were stopped through the agency of rock-dust and moisture.A rock-dusted mine is one in which the floor, roof, and sides of every accessible working place, including haulage ways, airways, manways, and rooms and connections have an application of rock-dust - for instance, limestone - such that the incombustible content of the aggregate dust on those surfaces is over 60 per cent. The dust in these workings should be sampled at regular intervals to determine whether the incombustible matter in the coal-dust is less than the necessary minimum of 60 per cent; another application of rock-dust should be given when the incombustible percentage is less than 60. (As an example of thorough rock-dusting, see Bureau of Mines Information Circular 6578, 1932, which describes how rock-dusting is done in Alabama at a cost of 1.8 cents per ton of coal for a thorough application; Report of Investigations 3060, February, 1931, Rock-Dusting In A Pennsylvania Coal Mine; or Information Circular 6244, 1930, giving data, including costs, on rock-dusting in coal mines in New Mexico.)An explosion may be started by the ignition of gas, even when rock-dust is present; hence it is not correct to say that rock-dust will prevent an explosion of gas; however, if rock-dust has been applied to a working place which has present an explosive mixture of me-thane and air, and if an open light is used or a blown-out shot or an electric arc occurs, although there will very likely be an ignition and possibly an explosion, the rock-dust will certainly prevent ignition of the coal-dust nearby, and unless the general atmosphere has an explosive gas mixture, the rock-dust will stop propagation of the flame throughout the mine. In other words, if an explosion is started by gas or by coal-dust and the mine has been rock-dusted as defined, the rock-dust will prevent widespread extension of the explosion, unless the general atmosphere contains methane and air in explosive proportions.With these definitions clearly in mind, instances are now given where rock-dust has played a prominent part in the stopping of several explosions. No cases have been included where there was any reasonable doubt that rock-dust had taken a definite part in the limiting of the explosions."

Apr 1, 1932

By Howard M. Stainer

Jan 1, 1963

By Howard M. Stainer

[Cover Page]

Jan 1, 1963

Provide ear protection which allows normal, unaltered hearing at low noise levels, yet protects the wearer from excessive noise. The Approach: A commercial earmuff with integral speakers has been adapted with a special amplifier so that low sound levels are not affected, but higher noise levels automatically reduced. How It Works: The discriminating earmuff developed by the Bureau of Mines has two modes of operation. In the first mode, where input sound levels are less than or equal to 83 decibels, the wearer will perceive noise at its actual level. For inputs in excess of 83 decibels, the second mode of operation begins and the sound perceived by the wearer is progressively attenuated, or reduced, as the input level is increased. A recognizable difference still exists between two adjacent sound levels enabling the wearer to differentiate between them.

Jan 1, 1975

By C. Lorimer Colburn

"High explosives are generally shipped in stout wooden boxes of convenient size, which are much sought after by miners and others for miscellaneous uses after they are emptied. The management of most mines has no fixed policy for the disposal of used dynamite boxes and will allow any one to carry them away. Many dynamite boxes are nailed up in the mine buildings or underground to serve as shelves and cupboards. Some are used as receptacles for odds and ends, and others are used in taking samples.Although used explosives containers are so generally put to beneficial service, there is nevertheless an element of danger in their use. Dynamite boxes are particularly dangerous. Very often nitroglycerin exudes from the dynamite sticks and is absorbed by the wood of the box. Such boxes are dangerous because they are very explosive. Although a box that has not absorbed nitroglycerin is safe, yet there is always the danger that a person will get a box that is partly saturated.On account of this danger, all mining companies should use extreme care in giving away used explosives containers. Some one individual who is acquainted with explosives and their peculiarities should act as inspector for every container given away. This job may best be handled by the man in charge of the powder magazines. A box that shows any stain of nitroglycerin should be destroyed by fire. The other boxes that are free from nitroglycerin or dynamite can be used."

Jun 1, 1920

By Harry F. Weaver

Rivers in industrial and raining areas frequently are contaminated by material dumped into them causing the water to carry in suspension large amounts of silt, which subsequently is deposited alone; the banks and, ultimately on the agricultural lands if the water is used for irrigation purposes. Two common examples of this practice are the dumping of breaker refuse in the anthracite region of Pennsylvania and the dumping of tailings from the metallurgical mills in various metal-mining districts. Studies in stream pollution and its resultant problems are very important, and surveys are constantly being made by Federal and State agencies, as well as by private companies, to determine the quantity of solids actually being carried by these watercoarses. These studies require accurate sampling of the silt-carrying water to determine the amount of solids within reasonable limits. A device that will obtain reasonably accurate samples of material from silt-bearing streams is described in this circular.

Jan 1, 1943

By S. H. Ash

California leads the Nation in the number of operating metal mines and the small number of persons employed at individual mines, which reached a minimum irk 1932 with an average of seven men. The mines are scattered over the entire State, which is the second largest in area (155,562 square miles) in the United States. The mines are situated at various altitudes, with portals ranging from approximately 300 feet below sea level to almost 12,000 feet above. Many of the mines can be reached only during the summer, while at others the heat of the regions adds so the difficulties during the summer months Supplied of explosives the use (or, probably more correctly, the misuse) of which constitutes one of California&apos;s gravest mining problems; are handled and stored under condition that contribute many hazards. The problem of providing medical care is serious and complicated, especially at small mines and more particularly in the almost inaccessible mountainous regions; instances in which a knowledge of first aid would have been beneficial but was lacking, or when first aid was instrumental in saving life or limb because it was available are too numerous to be mentioned.

Jan 1, 1936

By M. H. Stanczyk

Bench-scale laboratory tests were made by the Bureau of Mines of a segregation-flotation concentrate, assaying 20.43 percent copper, to investigate the influence of various ratios and concentrations of ammonia and carbon dioxide on copper extraction. Leaching the concentrate with a solution containing 900 pounds of ammonia and 360 pounds of carbon dioxide per ton of feed, followed by washing the leach residue with 1.75 tons of a 10-percent solution of ammonium carbonate and about 1 ton of water (as steam) per ton of solids, resulted in a copper recovery of 96.3 percent. Resegregation and flotation tests of the washed residues revealed that 85 percent of the copper in the residue could be recovered. Steam distillation tests of a typical ammoniacal leach liquor, assaying 39 grams copper, 105 grams ammonia, and 77 grams carbon dioxide per liter, recovered over 99 percent of the copper as a mixed oxide-carbonate precipitate. The ammonia losses in leaching, filtering, washing, and distillation were 0.12 pound per pound of copper recovered in the precipitate. Calcination and subsequent hydrogen reduction of the precipitate yielded a metallic copper powder assaying 98 percent Cu, 0.87 percent Si02, 0.10 percent MgO, 0.54 percent CaO, and 0.41 percent R203.

Jan 1, 1961

By Deborah A. Spotts

Researchers at the Bureau of Mines have developed a technique for re- generating chromic acid-sulfuric acid etching solutions used in metal surface treatment operations. The technique utilizes a diaphragm cell equipped with a cation-selective membrane to oxidize cr3+ to cr6+ at the anode and to remove copper, the major metallic contaminant, at the cathode. Normally, spent etchant is discarded after approximately 3 days of use. Using the electrolytic cell, the etchant can be used for a year without replacement, From data obtained from industrial-scale cells, the installation of a regeneration cell with a 1,000-gal catholyte- holding tank has been estimated to save at least $240 per day, The payback period for the investment is estimated to be about 10 mo or less. Because the magnitude of these cost savings will vary at different locations, several graphs are presented to aid in calculating payback for a specific site. Using these graphs and the capital costs presented in this study, the payback period can be determined for installing a regeneration cell with a 500- or a 1,000-gal catholyte-holding tank in an existing surface treatment plant.

Jan 1, 1983

By N. S. Dalal, V. Castranova, K. Van Dyke, V. Vallyathan

"IntroductionInhalation of crystalline silica is often associated with the development of pulmonary disease (Ziskind et al., 1976). Recently, it has been proposed that freshly sheared silica .may have surface properties that make it more reactive with lung tissue than aged silica, and that this unique reactivity ·of freshly crushed silica enhances its pathogenicity. A recent study in our laboratory strongly supports this theory (Vallyathan, et al., 1988a; 1988b). We found that grinding of silica cleaves bonds in a silica tetrahedral lattice generating reactive free radicals sites on the surface of the silica particles. The presence of surface radicals on freshly ground silica was monitored by electron spin resonance (ESR) spectroscopy. The ESR signal generated from fresh silica in air is characteristic of Si-0 and Si radicals. Evidence, i.e., the ESR signal after the addition of a spin trap (DMPO) and its sensitivity to ethanol, indicates that these silicon-based surface radicals can react with water to form hydroxyl radicals (OH). Results also indicate that these surface radicals make fresh silica more cytotoxic than aged silica; i.e., fresh silica causes more membrane damage as evidenced by hemolysis and lipid peroxidation. Therefore, the presence of reactive sites on the surface of freshly cleaved silica may play a significant role in its pathogenicity.If surface· free radicals are related to cytotoxicity, then screening dusts for the existence of such radicals may predict their relative pathogenicity. Since an ESR spectrometer is not available to many laboratories, the objective of this study was to develop a quick and simple technique to monitor the existence of reactive surface sites on dust. The technique chosen was the measurement of chemiluminescence using a liquid scintillation counter; i.e., an instrument which·would be accessible to most investigators."

Jan 1, 1989

By D. D. Bolstad

This report describes the construction and use of a direct-reading azimuth protractor (DRAP) by the Bureau of Mines for measuring fracture orientations in mines, tunnels, or other excavations having a magnetic environment. The DRAP allows a rapid and simultaneous measurement of dip and azimuth of dip of a fracture plane. The instrument is rugged, lightweight, and easily constructible from standard hardware items. The DRAP can measure dip to within ±0.5° and azimuth of dip to within ±5° of corresponding values obtained with a Brunton compass.

Jan 1, 1974

By John Nagy

This circular has been prepared for the guidance of safety engineers, shot firers, and coal-mine inspectors concerning multiple blasting with short-delay (millisecond-delay) detonators. These special precautions are suggested in addition to those normally followed in blasting, as outlined in the Federal Mine Safety Codes 5 6/ and in Miners&apos; Circular 58.7/ INTRODUCTION The use of short-delay blasting has been proposed for promoting safety and increasing the rate of production in coal mining. Ideally, short-delay blasting, as compared with equivalent single-shot blasting, reduces exposure of the shot firer to dust, fumes, and weakened roof; as compared with equivalent simultaneous blasting, it reduces roof disturbance.

Jan 1, 1959

By Gerald A. Munson, E. P. Barrett

Rapid and accurate estimation of the proportions of mineral in rock mix- tures is essential in mineral-dressing research and industrial operation. Estimation of the proportions of potash and soda feldspars in ground pegmatite material by casual observation is almost impossible and may be tedious or even difficult by petrographic examination. Chemical analysis may not be an accurate measure, as pegmatite rock may contain the following minerals:

Jul 1, 1947

By David Ingram

The results from the sound level measurements, the dosimeter recordings and the time-activity studies on four different air-rotary rigs indicate a wide variation of operator noise exposure during hole development. These variations appear to be dependent on the cab design and the operator?s drilling behavior. Studies have documented that exposure to high sound levels for long periods of time can cause hearing loss. The results of this study help identify the loudest parts of the drilling cycle. Sound level measurements on the four rigs show that all the rigs generate sound levels that are 90 A-weighted decibels (dB(A)) and above within 6 feet around the rigs during drilling. It is easy to conclude that some type of noise protection, such as a cab, is needed to protect the operator from overexposure to noise for an eight-hour shift of uninterrupted drilling. However, even when rigs are outfitted with cabs, operators observed in this study are being exposed to sound levels above 90 dB(A) during some activities required to complete a drilling cycle. An evaluation and comparison of the four dosimeter recordings and time-activity studies during one drilling cycle may explain why variations in operator exposure occur. Table 1 summarizes the time-weighted average (TWA) and accumulated dose percentages for each of the four operators during the time needed to complete one typical hole cycle.

Jan 1, 2008

By Dorsey A. Lyon

At the main experiment station of the U. S. Bureau of Mines , situated in Pittsburgh, Pa . , three phases of its work in behalf of the safety of the coal miner are the establishment of permissible explosives for use in gaseous and dusty mines , the development of electrical equipment that can be used with safety in mines of this character , and improvement in the safety of mechanical devices used in and about the mines . Also That these efforts are beginning to have a cumulative effect in lives. saved is evident from the fatality statistics of the industry . Although nearly 80,000 more men are employed in coal mining than ten years ago and much more coal is mined , the fatalities each year are considerably less than ten years ago . the amount of coal mined in a year for each life lost has risen between 60,000 and 70,000 tons . In 1909 , the year before the Bureau was created , the production of coal for each life lost was 174,416 tons . In 1920 , the production for each life lost was 285,000 tons .

Mar 1, 1921

By Harold L. Gibbs

The purpose of this paper is to encourage petrographers to prepare thin sections, as the demand for microscopic examination of rocks, ores, and metallurgical products is becoming more general in .the mining metallurgical-fields. This paper has been written with the knowledge that the successful thin-section methods and the several new techniques herein described will be helpful to all engaged in this field of work. Detailed instructions for making thin sections by methods developed at the Salt Lake-City laboratory of the Bureau of&apos; Mines are given in this paper. Several new techniques are described for making thin sections of loose grains and fine sands and for making good thin sections of highly altered and friable rocks. The methods described insure superior bonding of the rock to the glass slide, thus virtually eliminating any failures due to parting of the section from the glass slide, and permit fast mounting, grinding, and finishing, thereby materially lessening the time required to prepare thin sections.

Jan 1, 1950

By Charles L. Kimbell

The series summarizing the prices of the major nonferrous metals on the stock exchanges of the United States and the United Kingdom has been continued this year in tables 23 and 24. As a result of the lack of availability of comprehensive data on the prices of metals in Canada, the table that had presented that information in past years in this chapter has been discontinued and the price series for nickel that had been in that table now appears in the table presenting metal prices in the United States.

Jan 1, 1993

By F. D. Osgood, A. C. Fieldner, W. A. Selvig

In connection with investigations being conducted by the Bureau of Mines regarding pulmonary disease which is prevalent among metal miners in certain districts , a large number of rock- dust samples have been collected , and have been examined in the Bureau's laboratories . The earlier work has been described in Bureau of Mines Technical Paper 105 , " Pulmonary disease among miners in the Joplin district , Missouri , and its relation to rock dust in mines " by A. J. Lanza and Edwin Higgins , 1915 , and in Bureau of Mines Bulletin 132 , " Siliceous dust in relation to pulmonary disease among miners in the Joplin district , Missouri , " by Edwin Higgins , A.J. Lanza , F.B.Laney , and Geo . S. Rice , 1919. The methods of collecting and examining dust samples have been greatly improved during the investigation , much valuable information having been made available by similar investigations conducted by the Miners ! Phthisis Prevention Committee , Union of South Africa . The latter are described in the " General report of the Miners ' Phthisis Prevention Committee , Johannesburg, Union of South Africa , 1916 " , and " Final report of the Miners ' Phthisis Prevention Committee , Johannesburg, Union of South Africa , 1919. " The investigations by the Bureau of Mines and the South African committee show that by prolonged inhalation of air containing minute particles of sharp and insoluble rock dust , the lungs retain sufficient dust particles to cause decided injury to the lung tissue , the injured lung becoming very susceptible to the development of tuberculosis .

May 1, 1920