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By Seth C. Schaefer

The Bureau of Mines investigated thermodynamic properties of Mn304 (manganomanganic oxide) and Mn203 (manganese sesquioxide). The standard Gibbs energies of formation (?Gf°) of Mn304 and Mn203 from their lower oxides were determined with high-temperature galvanic cells using stabilized Zr02 (zirconia) as the electrolyte. Potential measurements were obtained for the cell Pt, MnO, Mn304//Zr0 2//02(g, 0.0112 atm), Pt, with the overall cell reaction 6Mn0(c) + 02(g, 0.0112 atm) = 2Mn304(c), where- 02 refers to indicated partial pressure of oxygen at the reference electrode. Similar measurements were obtained for the cell Pt, Mn304, Mn203//ZrO2//02(g, 0.0115 atm), Pt, with the overall cell reaction 4Mn304(c) + 02(g, 0.0115 atm) = 6Mn203(c). Equilibrium oxygen pressures for the Mn0-Mn304-02 and Mn304-Mn203-02 systems were measured and may be expressed for the respective systems as [23,400 109 P02 T + 11.91 (764.9 - 1,208.6 K) and log p02 = - 11,957 + 9.66 T (968.6 - 1,208.2 K),] where pressure (p02) is in atmospheres and temperature (T) is in kelvins. Standard thermodynamic properties of Mn304 and Mn203 were derived from these measurements and auxiliary thermodynamic data from the literature.

Jan 1, 1982

By W. W. Weller

Heat-capacity measurements of sodium dimolybdate (Na2Mo207) and sodium ditungstate (Na2W207) were conducted over the temperature range from 51° to 298° K. The entropies of the two compounds at 298.15° K were calculated from the heat-capacity values and were used, in conjunction with other entropy data, to evaluate the entropies of formation of the compounds from their constituent elements and oxides.

Jan 1, 1963

By R. F. Abernethy

A chemical method of determining microgram quantities of arsenic in coal was investigated by the Bureau of Mines to supplement a semiquantitative spectrographic method of determining arsenic in coal ash. In accordance with a method recommended by the International Organization for Standardization, 1-gram samples of coal are decomposed by wet oxidation with boiling sulfuric acid (H2S04) and nitric acid (HN03) to remove the organic matter. After heating to fumes of SO3 to remove HN03, the arsenic is separated as arsine by the action of zinc in H2S04 solution. The arsine is absorbed in dilute iodine solution in which the arsenic is determined colorimetrically by the molybdenum-blue reaction. Two modifications of the method for obtaining the arsenic in solution, in addition to the wet oxidation method, give satisfactory results. The modifications are (1) furnace ashing with MgO added to the coal, followed by treatment with H2S04, and (2) extraction of arsenic from the coal by dilute HNO3 without ashing. Float-and sink-tests show that arsenic is associated mainly with mineral matter in the three coals examined. High-temperature ashing tests show that very little arsenic is volatilized from coal ash below 1,000° C, but it is virtually all removed from the ash at 1,300° C.

Jan 1, 1968

By L. W. Brandt

As part of its objective to expand the body of mineral information as a basis for new technology, the Bureau of Mines conducted research on the fundamental behavior exhibited by phosphate clay waste in settling ponds. A semiempirical equation used to describe the compaction of ceramic powders in a single-acting die was applied to aqueous phosphatic clay waste and attapulgite slurries. This equation, [*V = a1 e ?k1/P + a2e ? k2/P] was found to describe the compaction of an attapulgite gel and a phosphate slime gel by a moving screen. [*V] is the ratio of the compaction achieved at a given pressure, P, to the compaction achieved at a pres-sure sufficient to remove all space between particles. The constant al represents the fraction of compaction achieved at low pressure by rearrangement of floes to higher packing density, and a2 represents the fraction of compaction achieved at higher pressure resulting from removal of voids within floes. K1 and K2 are constants determined from the experimental data. Both the low-pressure and high-pressure compaction mechanisms were observed in the compaction of the clays. These two compaction mechanisms offer an explanation for the observation that impounded slimes initially dewater rapidly and then dewater at a much slower rate.

Jan 1, 1982

By D. J. Parker

This report is based on data collected in and about the Liberty mine of the Liberty Fuel Co. by D. J. Parker and W. W. Kessler on December 13 and 14, 1933. An important phase of an examination to determine the general condition of a mine with respect to safety is the collection of dust samples from rock- dusted areas. Definite conclusions, based on intelligent interpretation of the analyses of such samples, can be reached only when the general condition of the mine is known. A similar examination and report were made on this property in January 1930 by D. J. Parker and R. I. C. Manning. Since that time much has been done by the management to improve safety conditions in this mine. The changes made will be noted in the course of this report. The mine is in Spring Canyon at Latuda, Carbon County, Utah, and is served by a branch line of the Denver & Rio Grande Western Railroad about 7 miles long and connecting to the main line near Helper, Utah. The writer desires to express his sincere appreciation for the many courtesies and helpful cooperation extended by Superintendent George Schultz and Mine Foreman F. W. Koelling.

Nov 1, 1934

By Larry J. Nicks

The Bureau of Mines is investigating the catalytic activity of rare-earth compounds to develop a catalyst for the cathode reaction of a hydrogen-oxygen fuel cell. This report presents the results of studies of the catalytic activities of lanthanide oxides for the oxidation of hydrogen at 150° to 250° C. Preliminary activity tests were made with approximately stoichiometric mixtures of hydrogen and oxygen diluted with helium. A series of tests was also run under oxygen-rich conditions in which specific rate constants and activation energies were determined. Variations in rate constants up to 2,000 times were observed for the various lanthanide oxides. The three most active catalysts were oxides of Ce, Pr, and Eu, having specific activities of 6.93 X 10-7, 4.88 X 10-7, and 4.06 X 10-7 moles H2.sec-1.m-2, respectively, at 200° C.

Jan 1, 1973

By Roy H. Grau

The National Institute for Occupational Safety and Health (NIOSH) has conducted research to improve the ventilation of large-opening mines whose entries are at least 93m2 (1,000 ft2). The ventilation of large-opening mines is unique compared to other types of mines because (1) it is challenging to keep airflow velocities high enough to effectively remove or dilute airborne contaminants because the entries are so large, (2) large air volumes can be moved through the mines with little static pressure drop, and (3) stoppings that are used to direct ventilation airflows are costly to construct and to maintain. The research results suggest that the ventilation of large-opening mines is improved significantly by incorporating ventilation planning into the mine planning process, using propeller fans to direct airflow, developing new stopping materials and construction methods, and using long pillars to eliminate crosscuts where possible.

Jan 1, 2009

1. In 2002, a total of 2,065 coal mining operations reported employment to the Mine Safety and Health Administration (MSHA). Coal mines comprised 14.2% of all mining operations. • Bituminous mines comprised 92.5% (n = 1,910) and anthracite mines 7.5% (n = 155) of coal mining operations. • More than 70% of all coal mines were located in three states: Kentucky (28.7%), West Virginia (21.7%), and Pennsylvania (20.1%).

Jan 1, 2004

By John J. Sammarco

This report (Safety File Guidance 6.0) is the eighth in a nine-part series of recommendations and guidance addressing the functional safety of processor-controlled mining equipment. It is part of a risk-based system safety process encompassing hardware, software, humans, and the operating environment for the equipment’s life cycle. Figure 1 shows a safety framework containing these recommendations. The reports in this series address the various life cycle stages of inception, design, approval and certification, commissioning, operation, maintenance, and decommissioning. These recommendations were developed as a joint project between the National Institute for Occupational Safety and Health and the Mine Safety and Health Administration. They are intended for use by mining companies, original equipment manufacturers, and aftermarket suppliers to these mining companies. Users of these reports are expected to consider the set in total during the design cycle. • 1.0 Safety Introduction (Part 1).—This is an introductory report for the general mining industry. It provides basic system/software safety concepts, discusses the need for mining to address the functional safety of programmable electronics (PE), and includes the benefits of implementing a system/software safety program. • 2.1 System Safety (Part 2) and 2.2 Software Safety (Part 3).—These reports draw heavily from International Electrotechnical Commission (IEC) standard IEC 61508 [IEC 1998a,b,c,d,e,f,g]and other standards. The scope is “surface and underground safety-related mining systems employing embedded, networked, and nonnetworked programmable electronics.” System safety seeks to design safety into all phases of the entire system. Software is a subsystem; thus, software safety is a part of the system’s safety. • 3.0 Safety File (Part 4).—This report contains the documentation that demonstrates the level of safety built into the system and identifies limitations for the system’s use and operation. In essence, it is a “proof of safety” that the system and its operation meet the appropriate level of safety for the intended application. It starts from the beginning of the design, is maintained during the full life cycle of the system, and provides administrative support for the safety program of the full system. • 4.0 Safety Assessment (Part 5).—The independent assessment of the safety file is addressed. It establishes consistent methods to determine the completeness and suitability of safety evidence and justifications. This assessment could be conducted by an independent third party. • Safety Framework Guidance.—It is intended to supplement the safety framework reports with guidance providing users with additional information. The purpose is to assist users in applying the concepts presented. In other words, the safety framework is what needs to be done and the guidance is how it can be done. The guidance information reinforces the concepts, describes various methodologies that can be used, and gives examples and references. It also gives information on the benefits and drawbacks of various methodologies. The guidance reports are not intended to promote a single methodology or to be an exhaustive treatment of the subject material. They provide information and references so that the user can more intelligently choose and implement the appropriate methodologies given the user’s application and capabilities. The guidance reports comprise parts 6 through 9 of the series and are listed below: [5.1System Safety Guidance (Part 6).—This guidance supplements 2.1 System Safety. < 5.2 Software Safety Guidance (Part 7).—This guidance supplements 2.2 Software Safety. < 6.0 Safety File Guidance (Part 8).—This guidance supplements 3.0 Safety File. < 7.0 Independent Functional Safety Assessment Guidance (Part 9).—This guidance supplements 4.0 Independent Functional Safety Assessment.] [ ]

Jan 4, 2006

By J. S. Tosh

An equilibrium study of the system potassium carbonate, potassium bicarbonate, carbon dioxide, and water has been conducted with solutions of 20-, 30-, and 40-percent equivalent potassium carboaate concentrations. These equilibrium data cover the operating range of the hot carbonate scrubbing system for removing carbon dioxide from gas mixtures. Such data are necessary to establish the limits of purification and are used to design absorption and regeneration towers. Values of K in the relationship K = (KHCO3)2/(K2CO3)PCO2 were determined for higher temperatures of 70" to 140° C. and greater concentrations, I 20 to 40 percent, than employed by previous investigators. For the 20- and 30-percent concentrations, K is constant at a given temperature; thus, once K has been determined the equilibrium pressure of carbon dioxide can be calculated for any conversion. Variation of & values with changing conversion was observed with the 40-percent solutions, so that equilibrium calculated pressures are less reliable from average K values.

Jan 1, 1959

By D. J. MacDonald

The Bureau of Mines has carried out investigations on a method for producing zirconyl sulfate solution from zircon sand, comprising (1) reacting zircon sand with molten NaOH, (2) leaching the resultant fusion frit with water to remove sodium silicate and to convert sodium zircon-ate to hydrous zirconium oxide, and (3) leaching the hydrous zirconium oxide from unreacted sand with hot, dilute H2S04 to produce crude zirconyl sulfate solution. The following conditions were found to be suitable: reacting 0.6 kg of NaOH per kilogram of zircon sand for 10 min at 600° C; leaching the frit with 3 to 4 liters of water per kilogram of solids; leaching the residue with 5.1 liters of water and 1.25 liters of 98-pct H2S04 per kilogram of original solids for 10 min at 90° C; and filtering or decanting to recover unreacted zircon sand. A preliminary cost estimate is included.

Jan 1, 1982

By P. R. Bremner

The United States is more than 90 pct dependent on imported bauxite a source for aluminum, but it has vast nonbauxitic aluminum resources, such as kaolinite, anorthosite, alunite, etc. As part of a program to devise processes for treating these resources, the Bureau of Mines investigated a bench-scale leaching process using hydrochloric acid (HC1) and fluoride to extract aluminum from Wyoming anorthosite. HC1 and fluoride-to-aluminum (F/Al) mole ratios were studied with respect to aluminum extraction for single-stage, cocurrent, and countercurrent leaching modes. Using 95 pct stoichiometric HC1 and a F/Al mole ratio of 0.27, 90 pct of the aluminum was extracted by countercurrent leaching. Single-stage leaching with the same amount of acid and fluoride extracted 48 pct of the aluminum. Three fluoride sources, CaF2, Na2SiF6, and H2SiF6, were used and gave similar results on aluminum extractions.

Jan 1, 1982

By P. R. Bremner

In keeping with its mission to maximize mineral and metal recovery from domestic sources, the Bureau of Mines investigated a method to extract silver from tailings not amenable to cyanidation. Results of a laboratory study on the recovery of silver from cyanide tailings containing 1.7 ounces of silver per ton by leaching with an acidic ferrous chloride-sodium chloride solution are presented. The effects of reagent concentration and reaction time on the leaching of silver were investigated. A leaching solution containing 5 wt-pct NaCI, 2.5 wt-pct FeCI2, and 1.2 wt-pct HCI (for acidity) extracted 82 pct of the silver from the tailings during a 24-hour leach. The amount of HCI consumed during the leach was 46 pounds of HCI per ton of feed. Only 23 pct of the silver was extracted by conventional cyanidation. Ninety-nine percent of the silver was recovered from the pregnant solution by cementation onto iron powder.

Jan 1, 1982

By R. D. Currie

"INTRODUCTION Compressed air for operating coal-mining equipment is seldom considered in conjunction with modern methods and appliances. But the Jamison Coal & Coke Co. has proved the economy and efficacy of compressed air for this purpose at its Mine 8 near Farmington, 8 miles west of Fairmont, Marion County, W.. Va., and the mining industry as a whole concedes its superior safety in gassy or dusty coal mines.The uses for compressed air in coal mining are now generally associated with such equipment as coal punchers, chain-breast machines, and to a lesser extent the ""radialaxe"" type of mining machines.Electricity has rapidly superseded compressed air for power in coal mines during the past 20 years; and in the last few years the general, and often unwise, use of electricity at the face region has taken on added impetus through the widespread use of mechanical loading equipment.Some of the unfavorable results of this increased use of electricity are shown in the growing number of mine explosions and fires of electrical origin. In the past four years 59 explosions of this type took the lives of 672 men, or 74.8 per cent of the total number of deaths from explosions were due to explosions of electrical origin.3In 1926, an explosion in Mine 8 of the Jamison Co. killed 19 men. The exact source of ignition was not determined, although it was definitely decided that it was of electrical origin and probably was at an electric coal-cutting machine.Prior to this disaster the company had done some experimenting with compressed-air-driven mining machines, and its Mine 9 had been completely equipped with air-driven chain-breast machines; a few of these machines were also in use in Mine 8. The explosion, however, gave impetus to the adoption by this company of compressed air for operating face equipment. The chain-breast machines were as satisfactory as electric machines of the same type; but the trend in the industry was toward faster cutting machines, which required less physical exertion on the part of the operating crews. A track-mounted machine of the arcwall type was found to be suitable for the conditions and system of mining, so that one of these operated by compressed air was developed by the Jeffrey Manufacturing Co. working with the officials of the Jamison Co.The first of these machines was installed in the latter part of 1926 and additional machines were delivered from time to time, until at present there are nine of them in the mine. Necessary improvements have been made, with the result that a fast-cutting, easily handled, efficient, and safe mining machine has been developed for cutting the hard Pitts¬burgh bed coal of the Fairmont field."

Oct 1, 1932

By R. H. Lien

The Bureau of Mines, U.S. Department of the Interior, has developed a flue gas desulfurization process as part of its goal of minimizing the undesirable environmental impacts associated with energy and mineral-processing plants. This process, known as the citrate process, involves absorption of sulfur dioxide (SO2) in a buffered solution of citric acid. The S02-loaded solution is regenerated by reaction of the S02 with hydrogen sulfide (H2S) to form elemental sulfur. As an adjunct to the citrate process, bench-scale research has shown that S02-loaded citrate or glycolate solutions can be regenerated by countercurrent contact with steam (stripping) in packed towers. Concentrated S02 is produced by condensing the steam from the stripper product. Thus, steam stripping provides strong S02 gas for liquefaction, sulfuric acid production, or reduction to elemental sulfur. Stripping steam requirements were determined for treatment of 0.25-, 0.50-3 1.0-, and 2.0-pct-S02 waste gases. Steam requirements decreased with increasing S02 concentration n the simulated waste gases. For example, 5 grams of steam per gram o S02 was required to remove 90 pct of the S02 from a simulated copper smelter gas (2.0 pct S02), while 30 grams of steam per gram of S02 was needed for 90 pct S02 removal from a simulated coal-fired powerplant gas (0.25 pct S02).

Jan 1, 1979

By MINE SAFETY BOARD

Mining men and State officials in their efforts to make mining safer are confronted from time to time with various complicated questions . In recent years these questions have tended to increase with the use of mechanical appliances . Twenty- five years ago electricity had hardly been used in mines . To - day there is practically no other means of transmitting energy employed in American mines , except in metal mines where compressed air is used for drilling and small portable hoists . In coal mines there has been a great increase in mechanization and a tendency to concentrate the mining operation , which has resulted in attendant difficulties of ventilation and intensified the danger of coal - dust in bituminous and subbituminous mines . The answers to the questions which arise are not always obvious , as is shown by the fact that even able , experienced men differ in their opinions of the best way to overcome a particular mining hazard . The difficulty of solving the problems is also demonstrated by the varying provisions in mine safety rules , both in official regulations and in the rules of those mining companies who are endeavoring to do more than follow the letter of the law . Such differences of opinion on the best way of meeting a difficult situation are often found within the same mining organization , and so it has been in the Bureau of Mines .

Nov 1, 1929

By R. V. Ramani, P. M. T. White, D. Sutton

4.1 Introduction Using methods outlined in previous sections of this report, programs were written and/or obtained to: i) select best combinations of "a" and "k" for up to 8 different value parameters, ii) calculate available and unavailable ore tonnages and other statistics, and iii) produce contour maps of various parameter characteristics and available tonnages on a line printer. All the above programs are written in Fortran IV for execu¬tion on IBM 360/370 computers. 4.2 Calculation of Coal Reserves The Ore Reserve program suite consists of the following sections: (a) UNIT 1: This unit is a subroutine called by Unit 2 to determine values for "a" and "k" from the given data. (b) UNIT 2: These programs calculate ore reserves and are composed of a main program and several sub¬routines. In the following, their functions are abbreviated: i) MAIN - calls subroutines, reads run parameter variables, reads borehole data and interpolates grid node values for the area of investigation

Jan 1, 1974

By M. S. Seehra, R. S. Pandurangi

"A comparative study of the intensities of the IR modes in the pjlotoacoustic and. FrIR spectroscopy of amorphous and crystalline SiO2 particles is presented. It is observed that in photoacoustic spectroscopy of amorphous SiO2, IR modes of surface species are enhanced by over an order of magnitude compared to the bulk IR modes of SiO2. This effect, though not yet understood, may find applications in surface science.Since the publication of the Rosencwaig-Gersho theory of the photoacoustic effect in solids in 1976 [1], a great deal of attention has been paid to the development .of photoacoustic spectroscopy (PAS) into an analytical technique for condensed matter studies, especially when combined with the modern Fourier transform infrared (FTIR) spectrometer [2-8]. PAS has now been applied to a variety of experimental situations [2, 3] and it is particularly suitable for opaque powders and for cases where ~ample preparation (e.g. mixing with KBr as is usually done in FTIR spectroscopy) is not desirable. Another area of interest is the depth profiling feature of PAS, which is studied by varying the modulation frequency of the incident radiation [2-8]. The one-dimensional Rosencwaig-Gersho theory for non-porous samples has been extended to other cases [9-12]. Recently it has become known [11, 12] that for porous samples with porosity the IR modes are enhanced by a factor proportional toe. This enhancement is due to the pressure wave set up in the interstitial gas in the porous sample and this enhancement has been reported by a number of groups [12-14].In this Letter we report the observation of anomalously large enhancement of the PAS signal for certain surface IR modes on the surface of amorphous silica particles. This observation differs from the previous reports in that certain surface modes are enhanced by over an order of magnitude compared to the bulk IR modes. Although the reasons for this enhancement of the surface IR modes in PAS are not understood at present, this observation may open up new approaches to the study of surfaces. Results of these initial observations are given in this Letter. ·Experimental studies reported here were carried out on an FTIR spectrometer (Mattson Instruments, Model Cygnus 100) equipped with an MCT detector. The same instrument was used for PAS studies in conjunction with an MTEC (Model 100) PA cell. The sample cell and the spectrometer are continuously flushed with dry, CO2 free air obtained by the use of Balston Instruments Air Dryer Filter System (Model 75-60). Usually data were collected for 32 scans at 4 cm-I resolution, although both scan and resolution can be varied. For FTIR studies, samples were mixed with IR-grade KBr and pelletised. For PAS, no sample preparation is necessary and data are ratioed against dry carbon black [4, 5]."

Jan 1, 1989

By T. Whitrnoyer, J. Sneckenberger

"The acOustic impedances of seven rat lungs were measured at frequencies between 100 and 6400 Hz. Rats were divided into two groups: a silica exposed group (N=3) and a control group (N=4). The silica exposed group was injected intratracheally with silica solution. Three of the control group were intratracheallyinjected with saline. Between four and six weeks after theinjections, all lungs were excised and degassed. Lungs were,suspended in a pressure Chamber, with the trachea canula attached to the end Of a tapered impedance tube. The lungs were subjected to transpulmonary pressures between -30 cm H2O and 6 cm H2O to simulate deflation and inflation. With transpulmonary pressure being held constant, the impedance tube was excited with random noise. A dual channel analyzer calculated H12(f), the transfer function between the two microphones. This function was used to calculate the lung's impedance at that pressure. The impedance magnitude spectra of both groups typically had peaks at 2000,3500, and 5500 Hz. Statistically significant differences. (90%confidence level or greater) between the two groups occur at the 3500 Hz peak at transpulmonary pressures of 20, 8, 6, 4, and 2 cm of H2O. This fact seems to confirm that this method can detect. lung disease. Further research will indicate whether this method will be able to detect the onset Of coal worker's pneumoconiosis.INTRODUCTIONOne of the first studies of impedance Of the human lung were conducted by DuBois et al.[2] using the forced OscillatiOn technique. This technique, however, was limited to frequencies below 30 Hz. Further studies by Van Den Berg [6] revealed thatthe lung reflected higher frequency sounds (100-10,000 Hz), instead Of behaving as an anechoic termination. This discovery has lead to several studies of the acoustical properties of both human and animal lungs at high frequencies [3,4,5]."

Jan 1, 1988

By John J. Gordon, Neil K. Cooperrider

The International Organization for Standardization (ISO) standard ISO 2631 [1,2] provides three methods for evaluation of human exposure to vibrations that contain occasional shocks or impacts. Part 1 of the standard specifies the running r.m.s. or maximum transient vibration method (MTVV) and the fourth power vibration dose value (VDV). Part 5 of the standard provides a method of computing the stress in the lumbar spine for humans exposed to multiple shocks. Alem et al [3] have reported application of these methods to data for tactical ground vehicles. This paper reports and compares VDV and spinal stress evaluations of more than 90 hours of vibration and shock measurements on North American locomotives engaged in through freight operations. The measurements evaluated in this paper were obtained for full crew shifts on 19 freight locomotive runs on mainline track in locations from New York to California. The shifts ranged in duration from 187 minutes to 497 minutes. The average speeds for the shifts were from 21.0 mph to 54.6 mph. All measurements were made on locomotives hauling freight trains in regular revenue service. Data Acquisition and Processing The results reported here were computed using test data acquired from a tri-axial seat pad, accelerometer at a sample rate of 400Hz with an anti-aliasing filter corner frequency of 100Hz. The VDVs and the lateral and longitudinal spinal stress values were computed directly from the acquired test data according to the procedures specified and described in [1] and [2]. The vertical spinal stress values were computed by converting the as-acquired test data to a sample rate of 160Hz for input to the vertical spine model, as required in [2]. The conversion of the test data from the as-acquired sample rate of 400Hz to the required sample rate of 160Hz involved up sampling or interpolating the test data to an equivalent sample rate of 800Hz, band limiting the resultant data with a low-pass filter corner frequency of 60Hz and finally down sampling or decimating the 800Hz data to a sample frequency of 160Hz. Discussion The vertical VDVs computed according to [2] for the 19 shifts ranged from 2.68 to 9.33 m/s1.75. In all but one case, the vertical values were greater than the values for the lateral or longitudinal directions. Note that the health guidance in [1] puts the lower boundary of the health guidance caution zone at a VDV value of 8.5 and the upper boundary at 17 m/s1.75. The daily equivalent static compression dose computed following [2] ranged from 0.123 to 0.434 MPa. Health guidance provided in [2] states that there is a low probability of an adverse health effect if the daily dose is less than 0.5 MPa.

Jan 6, 2006