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Jul 1, 2003

To evaluate the effectiveness of dust collector bags for reducing dust liberation from a roof bolter dust collection system.

Jan 2, 2007

By W. D. Monaghan, G. L. Mowrey, C. W. Ganoe

In addition to developing various types of coal-interface detection system, the US Bureau of Miner is actively in involved in developing a coal rib-thickness monitoring system for highwall mining applications. One particular system that shows promise in a ground-pentetrating radar system to detect the coal-air boundaries of coal rifts. Based on preliminary laboratory and field tests results indicate that this method can be applied successfully in highwall mines to maintain constant rib thickness. The coal seam should be relatively clean in the vicinity of the antenna (e.g., have minimal partings or dirt bands) for best results.

By L. A. SCHOLL, J. K. CLEMENT

Among the problems investigated by the Bureau of Mines the coal- dust problem has received much attention. Several of the bureau's publications deal specifically with the subject. Bulletin 20° contains an account of preliminary experiments of the bureau to determine the explosibility of coal dusts as well as a review of pertinent literature. Bulletin 50 is a report of a laboratory study of the inflammability of coal dust. The first series of coal-dust explosion tests in the bureau's experimental mine at Bruceton, Pa., is described in Bulletin 56, and Technical Paper 56 presents notes on the prevention of dust and gas explosions in coal mines, and Technical Paper 84 discusses the causes of such explosions and describes methods and apparatus devised by engineers of the bureau for preventing and checking them. The present paper is a report of a detailed study of the bituminous dusts of Illinois mines, and is a part of the investigations conducted by the bureau in cooperation with the Illinois State Geological Survey and the department of mining engineering of the University of Illinois./ It is well known that bituminous coals like those found in Illinois yield dusts that may give rise to explosions of great violence. In order that proper methods might be devised for preventing dust explosions in Illinois mines it was considered desirable to obtain accu- rate information on the quantity and character of these dusts. Ex- periments and tests of dust explosions in an experimental mine as well as in a large steel gallery comparable in area of cross section to mine entries have been made by the Bureau of Mines. Similar experi- ments have been made in Austria, England, France, and Germany. Experiments under conditions similar to those of actual mining prac- tice are obviously more conclusive than tests made in a laboratory. On account, however, of the expense, time, and quantity of dust re- quired, it is not practicable to conduct large-scale tests in studying a large number of dusts and recourse must be had to laboratory apparatus and methods. Laboratory,devices for the study of coal-dust explosions have been devised by a number of investigators. Most of these were intended for qualitative tests only. Quantitative methods have been devised by investigators of the English and French mining-experiment stations." In the experiments described in this report, laboratory tests of inflam- mability were made with an apparatus devised by Dr. J. C. W. Frazer, formerly a chemist of the Bureau of Mines. Laboratory tests of inflammability have been made on more than 500 samples of dust from 100 representative Illinois mines. As a result of these tests it may be stated that: 1. The coals of Illinois when ground fine enough yield highly inflam- mable dusts which when suspended in air may give rise to violent explosions. 2. In the majority of the mines of the State the dusts adhering to the ribs are inflammable. In about one-fourth of the mines the quantity of rib dusts present in the entries is sufficient to form an explosive mixture with air. 3. Most of the road dusts are inflammable when ground to a suffi- cient degree of fineness.

Jan 1, 1916

By Thomas L. Chapman

The San Manuel is a deposit of low-grade disseminated copper ore. It was brought to the attention of the government in October 1942 through an application to the Reconstruction Finance Corporation for a development loan, supported by a report by Henry W. Nichols. Nichols' sampling of two outcrops containing copper silicate and his geologic map indicated that a minable body of copper ore might be developed. The Federal Geological Survey was requested to examine the property. The Survey mapped the geology in March 1943 and cut a few check samples, which substantially confirmed Nichols' sampling of the outcrops and a few shallow workings. The geologists of the Survey recommended some test drilling by the Bureau of Mines. The property was examined by the author and Wm. D. Hughes, associate engineer of the Bureau of Mines on March 22 and 26, 1943, and a preliminary drilling campaign was recommended. Five shallow churn-drill holes totaling 1,480 feet were put down under the supervision of Chas. A. Kumke, one of the Bureau's engineers, from November 23, 1943, to January 13, 1944. This work indicated that the deposit extended deeper than the 350-foot depth attained in the deepest hole and might have very considerable areal extent. Additional funds were allotted, and the drilling contract was extended twice to a final maximum of 17,000 feet with 2,000 feet maximum depth of hole. Drilling was continued by the Bureau of Mines until February 2, 1945, when 15,844 feet of hole had been drilled. The Magna Copper Co. took options on this and adjoining property in September 1944 and commenced drilling with two machines. It also engaged the two contract drills used by the Bureau after it stopped drilling. It exercised its options in August 1945 and organized the San Manuel Copper Corp. to operate the property. That company is continuing to explore the ore body with six churn drills. Thomas Lyon took options early in 1945 on holdings adjoining the San Manuel property on the east and is operating two churn drills. Exploration up to the completion of the last holes started by the Bureau of Mines indicated a block of ore 3,100 feet long, 400 to 800 feet wide, and 500 to 900 feet thick, and averaging about 0.8 percent copper. Subsequent drilling showed that the ore body extends considerably beyond this block. The axis of the ore body strikes about N. 61° E. Copper minerals are disseminated in hydrothermally altered quartz monzonite and monzonite porphyry. Ore outcrops in two small areas over the northeast part of the block. Elsewhere the copper-bearing rocks are capped by Gila conglomerate, which thickens toward the west and south. Drilling showed that the ore is in a thick, tabular body with a steep dip to the south. The ore body lies near the surface in the northeastern part of the block. The south side of the block is much farther below the surface than the north side. There the upper part of the copper-bearing rocks is lightly mineralized, so that the hanging wall of minable ore lies deeper than the base of the conglomerate cap, which thickens southward.

Aug 1, 1947

By J. W. Thompson

ORE CONCENTRATION PROCESS-PATENT OIL FLOTATION PROCESS. The invention of the patent issued to Sullman, Picard & Ballot November 6, 1906 (United States Letters Patent No. 835120), is based upon the discovery of an wholly unexplained phenomenon arising from the agitation of ore pulp containing oil and air in certain proportions. This was a discovery in an art in which it was well known that the elements of oil, air, and agitation possessed certain characteristics and produced certain results. As early as 1860 a British patent first suggested the use of oil in water concentration of ores by pointing out the affinity which oils have for metallic sub- stances in preference to gangue. Subsequently many patentees employed the known affinity of oil for metal in ore concentration proc- esses by using oil in proportions varying from 2 per cent to 300 per cent of the ore and recovering the oil-coated metal particles by causing them to rise to the top or sink to the bottom of the pulp. In these processes the agitation was either gentle or thorough but never great, and though always employed to produce thorough oiling of the metal it was used in different degrees for the sole pur- pose of causing the metal particles to rise or sink. In the prior art the oil was used for its known selective affinity for metal, agitation was em- ployed to mix the oil with the metal, and air was introduced to supple- ment the buoyancy of oil in raising oil-coated metal particles to the surface. To this extent had the art of oil flotation advanced when the patentee entered it, having reached the commercial stage in only two processes, representing respectively metal-flotation and metal-sinking processes, and having reached the stage of success in none. In the line of experiments by the patentee when the proportion of oil to ore was reduced to 1.5 per cent a "float" appeared; at 1.04 per cent still more "float" appeared; at 0.32 per cent the "float" again vastly in- creased; at 0.1 per cent the "float" again vastly increased. It thus developed that in using oil at 0.1 per cent or even at 0.05 per cent of the ore and after violently agitating the pulp from 24 to 10 minutes, there arose to the surface when the pulp was brought to rest, a thick froth or foam of oil-coated air bubbles carrying oil-coated metal particles to the extent of about 90 per cent of the metal con- tent, the foam being sufficiently stable to permit removal and metal recoveries. This was a new result based upon phenomenon then unknown and still unexplained and constituted discovery and promised a change in the art of oil flotation from laboratory experi- ments and mill failures to commercial success. The patent referred to covering the points mentioned has been sustained by the District and the Circuit Courts of Appeals and by the Supreme Court. Miami Copper Co. v. Mineral Separation, 244 Federal, 752, pp. 754-757. ORE CONCENTRATION PROCESS-OIL FLOTATION-INFRINGEMENT. The Miami Copper Co. in its process of concentrating ores by the oil flotation process used three distinct processes that were either the processes included and covered by the Sullman, Picard & Ballot patent or their fair equivalent and which were clearly an infringe- ment of the patent, and the company can not escape liability for such infringement by taking an additional step, although such additional step if taken alone would not constitute an infringement of the Sullman, Picard & Ballot patent. Miami Copper Co. v. Mineral Separation, 244 Federal, 752, p. 768. ORE CONCENTRATION PROCESS-VALIDITY OF GREENWAY PATENT. The patent issued to H. Greenway, June 9, 1914 (Letters Patent No. 1999699), is valid. The process disclosed in this patent was a substantial departure from processes of the prior art. The heating of water is a matter of large moment and the use of acids is a matter of constant and considerable expense. By wholly dispensing with both by the use of a minute quantity of hydroxy compounds, the patentee has disclosed an original and novel plan which has broad- ened and made more simple the agitation process of air flotation. The novelty and inventive character of Greenway's discovery is patentable.

Jan 1, 1918

Compare the fire endurance of paneled steel stoppings with that of traditional concrete block Stoppings. Background Permanent stoppings or partitions arc used in mines to separate ventilation airways. The ability of stoppings to retain their structural integrity for a minimum length of time under lire conditions and prevent the spread of flame and toxic combustion products to an adjacent airway is critical. The success of miners in reaching safety during a fire depends largely on the presence of uncontaminated airways. Traditionally, permanent stoppings for coal mines are constructed of concrete blocks. Recently, paneled steel stoppings that satisfy many of the requirements demanded of permanent stoppings, such as incombustibility and strength, have been introduced. Their use also introduced concerns such as the ability of a steel stopping to maintain its ventilation control function when exposed to a fire and the potential that the fire could transmit enough heat through the stopping to ignite combustible materials on the unexposed side. To address these concerns, the Bureau of Mines investigated the fire endurance of galvanized steel and concrete block stoppings.

Jan 1, 1989

By R. H. Grau

Improving the air quality in metal/nonmetal mines is important in protecting the health of miners. Air quality can be improved in metal/nonmetal mines by developing proper ventilation techniques. Mine ventilation systems require stoppings to direct the airflow and establish pressure differentials throughout the mine. Due to their large size, stoppings in large-opening mines are cumbersome and costly to construct and maintain. As part of its mining health and safety program, the National Institute for Occupational Safety and Health (NIOSH) designed and tested two novel stoppings (Super Stopping and the EZ-Up Curtain Stopping) at its Lake Lynn Laboratory (LLL). The Super Stopping is designed as a long-term permanent stopping for use in the main entries of the mine, while the EZ-Up Curtain Stopping, although very durable, is designed more for portability and ease of installation. This paper describes the design, materials, and construction methods used for these stoppings as well as their performance and durability when subjected to tests simulating actual production face blast pressures.

Jan 1, 2006

By Oscar Lee

"Flotation is generally regarded as a process that is only applicable to metallic minerals. However, its scope is now known to be greater than this, because some of the nonmetallic minerals are floatable, such as graphite, sulphur, and fluorite. Recent observations show that limestone may be added to the list of floatable nonmetallic minerals. Such work is being done on a laboratory scale at the Southern Experiment Station (Tuscaloosa, Ala.) of the Bureau of Mines, Department of Commerce, where experimental magnetic concentration of the low-grade iron ores of the Birmingham district is in progress. Certain experiments have demonstrated that the limestone may be floated from the magnetic log-washer tailing, and then incorporated in the iron concentrate.If the loss of lime could be prevented, some ores though low in iron and high in insoluble contain enough lime to make their concentrates self-fluxing. Since this loss in the magnetic log-washer can not be avoided, the Time must be recovered from the tailing by some method and added to the magnetic iron concentrate before sintering. Then the resulting concentrate will be self-fluxing.While seeking a suitable means of treating the tailing for recovery of lime, flotation was tried. It was at once evident that this method had possibilities, during the early part of the investigation, soap solution made from a common soap was used as a flotation reagent. The froth obtained was a fairly good lime concentrate. This result was an important clue, and led to tests with the use of such reagents as oleic acid and sodium oleate. Later, cresol, creosote, coal tar and other similar flotation reagents were tested in combination with the oleic acid and soap solutions. As a result, oleic acid and cresol used together were found to be satisfactory.The tailing from the magnetic log-washer is in excellent physical condition fur flotation. The iron ore had been ground in a ball mill to 100 mesh for magnetic concentration. Hence the bond between the lime carbonate and the other constituents of the tailing was well broken."

Apr 1, 1926

By Rudolf E. Greuer, Linneas W. Laage, Xinton Chang

MFIRE is useful for the analysis of ventilation networks under thermal and mechanical influence MFIRE simu¬lates a mine&apos;s ventilation system and its response to altered ventilation parameters, external influences, and internal influences Extensive output enables detailed quantitative analysis of the effects of the proposed alteration on the ventilation system MFIRE was written in FORTRAN 77 and compiled with Microsoft° FORTRAN for the Intel 8086-8088 central processing units The source code is listed in appendix A for users who wish to modify the source code for operation on other computers MFIRE MODIFICATIONS OF MTU-BOM CODE The program described in Bureau of Mines Informa¬tion Circular 8901 has become known as the MTU-BOM codes MFIRE is an evolutionary product of the MTU¬BOM code with major improvements and enhancements 6 For users previously familiar with the MTU-BOM code, the following is a listing of the major improvements and enhancements incorporated by MFIRE 1 The length of an airway is an input value, LA The elevation difference of the airway is calculated from the elevation input, Z, in both programs It is possible for a data file to describe an airway that is shorter than its el¬evation difference The MTU-BOM code does not check for this error and uses the values of LA and Z This does not cause a computational problem, only a simulation problem MFIRE issues a warning message for this case, and the airway length is made equal to the elevation dif¬ference if LA is less than Z 2 To evaluate rock temperatures (average wall surface temperature of airway before a fire), it is assumed that the air temperature at an airway entrance is equal to the air temperature at the airway starting junction, and that the air temperature at the airway exit is equal to the air tem¬perature at the exit junction. The MTU-BOM code follows this assumption in all cases When a rock temperature of less than 0° F is calculated, an average temperature is used to represent the rock temperature of the airway MFIRE uses the same principle, except the consideration of unlikely rock temperatures When the exit junction of an airway is the atmosphere (a fixed condition junction), the air tempera¬ture at the exit is made equal to the air temperature at the airway beginning If an unlikely value of wall temperature (<0° F or > 150° F) results from calculations, a message is issued and the rock temperature is set equal to the air temperature at the airway exit The program user can always input rock temperature (TROCK) for an airway to override the calculated value. 3 MFIRE allows use of an optional reference airflow rate to define and limit the heat generation of a fire source This allows the simulation model to more closely resemble a real fire and to improve simulation conver¬gence Heat generation corresponds, but is not linearly related to airflow rates reaching the fire In the simula¬tion, heat generation is calculated from oxygen consump¬tion and is directly related to the variable incoming airflow Use of this optional reference airflow rate allows the heat generation to vary, but in a damped, user defined manner When the airflow rate passing through a fire source is equal to its reference airflow rate, the data items describ¬ing the fire source are not modified If the airflow rate is lower or higher than its reference airflow rate, the data items used to define the fire source are modified according to the following equations

Jan 1, 1990

By M. Kanda, J. W. Adams

A system for measuring amplitude probability distributions (APD’s) of electromagnetic noise in coal mines is described and typical APD’s from an underground coal mine are presented. The APD is a basic statistic required for the design and analysis of communication systems, especially those intended for use in noisy environments, and where neither overdesign nor underdesign is acceptable. The rms and average field strengths are obtained by integration of the APD, and examples are shown at several frequencies. All field strength levels are given in absolute units. Selected frequencies cover the range from 10 kHz to 32 MHz.

Jan 1, 1973

Illinois has the largest reported bituminous coal resources of any state and is one of largest coal-producing states in the nation. Coal-bearing rocks underlie about 65 percent of Illinois, including all or part of 86 of its 102 counties. An estimated 18 1 billion tons of coal resources are still in the ground. Using present mining methods, more than 30 billion tons of coal are classified as recoverable. This represents almost one-eighth of the total recoverable reserves of all types of coal in the United States. The state&apos;s surface mining regulatory program was conditionally approved June 1,1982. It received full approval October 25,1988. The Abandoned Mine Land Program was approved June 1, 1982, and the AML emergency authority June 11, 1984.

Jan 1, 1992

By Joseph E. Chilton, Robert J. Timko, Charles D. Taylor

No regular monitoring of methane is required in areas of gassy coal mines outby the mining face. Methane ignitions that have occurred in mine outby areas indicate the need to provide better protection to workers. Handheld methane monitors are now used by some miners to make periodic measurements of methane at the working face. The IYONI II gas detector which is incorporated into a miner’s cap lamp and worn on a miner’s helmet can continuously provide an alarm signal whenever methane levels exceed a set level. Tests were conducted to evaluate the performance characteristics of this methane detector by measuring response times with methane gas supplied through a calibration fixture or adaptor. Other response time tests were performed with the detector in an environmental test box. Performance was also evaluated in a full scale test gallery where face methane emission and underground ventilation were simulated. Procedures for calibration by response time measurement of the IYONI II detector have been developed. In limited testing, the IYONI II detector was found to reliably detect the presence of 1 percent by volume methane.

By Rudolf Kudlich

"During the coming winter, it is probable that many householders who have habitually been users of anthracite coal will be obliged to turn to some other fuel for heating purposes, because of the limited supply of anthracite. The next best fuel, from a standpoint of cleanliness and ease of operation, is coke, but here again the supply is inadequate and the householder will have to fall back on bituminous coal. Though bituminous coal has the dis¬advantage of being dirty to handle, requiring more care in firing, and of giving off considerable smoke, it will be more generally available, costs less, and in the better grades which will naturally find their way to the domestic market, is higher in heat value, and contains less ash than anthracite.Choice of CoalThere a variety of bituminous coals are available, the householder should choose a low volatile coal, such as New River, Pocahontas, or some other ""smokeless"" coal, or the British coal now being offered in the markets along the Atlantic seaboard. Though not necessary to have the coal sized, as is the case with anthracite, it will be found cleaner to use coal from which the fine dirt has been screened. If it is found that excessive dust is caused when firing the coal, this can be reduced by slightly wetting the coal at the front of the bin, as it is being used.Method of Firingusing bituminous coal instead of anthracite in the domestic furnace, it will be necessary to use an entirely different method of fir Instead of leveling the fuel bed and putting on fresh coal in an even layer over the entire fire box, the coked and partly burned coal remaining from the previous firing should be pushed as much as possible to one side of the box, and the fresh coal thrown into the empty side so as to leave some burning coal exposed. In this way the green coal is heated slowly, the volatile gases are given off gradually, and are ignited by the burninggoing to waste up the chimney unburned."

Oct 1, 1922

By Jami M. Girard, Ed Mchugh

Slope stability accidents are one of the leading causes of fatalities at U.S. surface mining operations. The Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) is currently conducting research to reduce the fatalities associated with slope failures. The purpose of this paper to discuss some of this research and to present potential new technologies for slope monitoring and design. The paper also briefly discusses various warning signs of slope instability, introduces the most common slope monitoring methods, describes the limitations of various slope monitoring systems, and presents some field results using some of this new technology.

By Rudolf Kudlich

"SUMMARYThe Ringelmann Smoke Chart fulfills an important need in smoke abatement work and certain problems in the combustion of fuels. A knowledge of its history and method of preparation is, therefore, of interest to many. Since instructions on its use are not shown on the recent edition of the chart, those included in this revision of the previous information circular, by Rudolf Kudlich, now are a necessary complement to the chart. More detail regarding the use of the chart is included than was given in the earlier manuscript.INTRODUCTIONThe Ringelmann Smoke Chart, giving shades of gray by which the density of columns of smoke rising from stacks may be compared, was developed by a Professor Ringelmann of Paris. Maximilian Ringelmann, born in 1861, was professor of agricultural engineering at l'Institute National Agronomique and Director de la Station d'Essais de Machines in Paris in 1888, and held those positions for many years thereafter.The chart apparently was introduced into the United States by William Kent in an article published in ""Engineering News"" of November 11, 1897, with a comment that he had learned of it in a private communication from a Bryan Donkin of London. It was said to have come into somewhat extensive use in Europe by that time. Kent proposed in 1899 that it be accepted as the standard measure of smoke density in the standard code for power-plant testing that was being formulated by the American Society of Mechanical Engineers.The Ringelmann Chart was used by the engineers of the Technologic Branch of the Federal Geological Survey (which later formed the nucleus of the present Bureau of Mines) in their studies of smokeless combustion beginning at St. Louis in 1904, and by 1910 had been recognized officially in the smoke ordinance for Boston passed by the Massachusetts Legislature."

Apr 1, 1955

This pamphlet and the enclosed video describe a safe, effective and economical method for removing dust from work clothes. Background Information Dusty work clothes can increase a worker’s exposure to respirable dust. Respirable dust is usually considered to be particles having an aerodynamic diameter of 10 microns or less and able to enter and deposit in the gas-exchange region of the human lung. A former U.S. Bureau of Mines report documented a 10-fold increase in worker dust exposure on a number of separate occasions from dusty work clothes.* It was found that once clothes become contaminated, they are a continual dust source until cleaned. The only MSHA approved method to clean work clothes requires a HEPA-filter vacuuming system which is very time consuming and difficult to perform effectively. Therefore, most workers use a single air hose (not MSHA approved) which can elevate dust levels for the worker, co-workers, and the work environment. A substantial amount of engineering technology has been developed that, when applied, can significantly lower respirable dust exposures of workers at mineral processing plants. But even with these improvements, some workers continue to exceed their permissible exposure limit. Elevated exposures increase the potential for developing debilitating or fatal lung diseases. ?e clothes cleaning method described within is an example of a continuing effort to reduce the potential for developing these lung diseases. Information about engineering research by the former U.S. Bureau of Mines and NIOSH can be found online at www.cdc.gov/niosh. ?is website can also be used for obtaining NIOSH information about health hazards associated with crystalline silica.

Reduce longwall shearer operator&apos;s dust exposure by selecting the best drum water spray sys-tem for minimizing dust generated durinq cutting. Approach Three of the most commonly-used drum water spray systems were installed on the same set of shearer drums and compared to determine which system best suppresses dust. The spray systems studied were: ? pick-point flushing ? cavity filling ? water-through-the-it Instantaneous and gravimetric sampling instruments were used to measure the respirable dust exposures of the shearer operators and dust concentrations downwind of the shearer. The Three Systems: Longwall shearer drums are routinely equipped with internal drum spray systems since these systems have been shown to be more efficient than external systems in terms of dust suppression per gallon of water applied. All U.S. longwall shearer faces utilize some type of internal water delivery spray system. The two most common systems are bit-or pick-point flushing and cavity filling. Pick-point flushing uses nozzles mounted in the bit blocks or in special blocks immediately in front of the bits. Cavity filling utilizes spray nozzles installed in a pipe manifold mounted on the drum hub between the scrolls or along the edge of the vane scrolls; water is sprayed radially from the manifold towards the adjacent vane scroll.

Jan 1, 1986

By Robert C. Hickman

"INTRODUCTION The Cline mine has been worked intermittently for copper and gold since 1895. Scheelite has recently been detected with the aid of a ""Mineralite"" on the old waste dumps of the mine. Four diamond-drill holes were drilled by the Bureau of Mines from August 13 to September 25, 1946. Results of this drilling showed the vein to pinch at depth and to carry no mineralization of economic importance.ACKNOWLEDGMENTSIn its program of investigation of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, does the actual investigation work, and prepares the final report. The Metallurgical Branch, Oliver C. Ralston, chief, analyzes samples and makes beneficiation tests.The project was under the general supervision of Mitchell H. Kline, chief, Raleigh Division, Mining Branch.Acknowledgment is due Dr. Jasper L. Stuckey, State geologist, for logging the drill core and to J. B. Zadra and associates, Metallurgical Branch, College Park, Md., for analytical determinations."

Feb 1, 1948

By Erica E. Hall, Robert H. Peters, Charles Vaught, Jon C. Volkwein

Coal Workers Pneumoconiosis is the leading cause of death due to occupational illness among coal miners. This disease is caused by miners’ exposure to respirable coal mine dust. A Personal Dust Monitor has recently been developed to provide near real time feedback to miners regarding the number of milligrams of respirable coal mine dust in the air they breathe. This paper was prepared by the National Institute for Occupational Safety and Health to document coal miners’ reactions to this new device, and how they make use of the information it provides. Structured interviews were conducted with 30 coal miners at four mines. A four-stage conceptual model of miners’ decision processes with respect to how they interpret and respond to the dust exposure numbers from their personal dust monitor is proposed. The stages are: Diagnosis, Action Planning and Intervention, Evaluation, and Institutionalization. The interview responses provide considerable support for the model. Most miners paid attention to Personal Dust Monitor feedback and made efforts to reduce their dust exposure. Their efforts included: changing where they positioned themselves, making ventilation system improvements, and using respirators more often. The 29 miners who reported having experience wearing both the old and new type of dust monitors were asked which dust sampling system they preferred. Eighteen (62%) preferred the new monitors, 7 (24%) preferred existing monitors, and 4 (14%) had no preference. The most frequently cited advantage of the new monitor is its ability to provide relatively quick feedback on dust exposure. Miners provided several suggestions for improving the design of the instrument.