| Show explosive fumes in metal mining mini ng BY D harrington AND B W two recent occurrences in western metal mines in each of which three men were killed due to breathing fumes from explosives have aroused keen interest among mining men not only as to the exact cause of such accidents hut but also as to possible preventive measures in sinking the forty five degree incline marsh shaft near burke idalio idaho on may 13 1920 a round of holes containing about sixty pounds of 40 per cent gelatin explosive was blasted by the night shift upon leaving at 1130 p in it was customary for the night shift to leave compressed air blowers open at the bottom of shaft until the compressor was shut down slightly before midnight presumably this was not done on the night of the as the fumes were so heavy in the shaft bottom on the morning of the that at about 8 superintendent bergen and one of the shaft men on oil reaching the shaft bottom were overcome abild and fell from the bucket into the sump containing about six feet of water and when two other men went down in the bucket a few minutes later to investigate one also fell into the sump and the other was barely able to reach the shaft collar the three bodies were later on recovered from the sump at p m june 10 1920 at the dominion mine colville washington a round of eleven holes containing about fifteen pounds of 60 per cent nitroglycerine explosive was blasted in a fifty degree raise about fifty feet above the main tunnel level by the shift going off for the night in this mine it was the practice not to try to blow out the fumes until just before the shift went to work the next morning although no work was being done on the night shift one of the raise men curious to ascertain the effect of the shots about p in wandered into the mine which was a tunnel only a few hundred feet in length and was missed by one of his companions about an hour later when three men tried to remove the body of the inquisitive miner two of them were also overcome ultimately these two and the first man were removed from the point at which all were asphyxiated asphyxia ted which was practically at the foot of the raise in this case the explosive was wag seven eighths nitroglycerine used because the ordinary one and one fourth gelatin was temporarily unobtainable though the holes were drilled for the larger sized stick the explosive too was about a year old while two of the eleven holes missed fire there was no obtainable evidence of burning of supervising mining alining engineer bureau of engineer bureau mines and metal mining of mines explosive but later on after blasting these two missed holes containing possibly three pounds of the explosive an air sample taken a few minutes after blasting and essentially at the point at which the three men had been asphyxiated asphyxia ted gave per cent CO or sufficient to cause death after having been breathed a comparatively few minutes it was thought locally that the deaths were due to other gases but analyses indicate strongly that CO was responsible dangers daily confronting men these accidents indicate forcibly a danger daily confronting men working in metal mines and especially in small or prospecting mines in one case the dangerous fumes were in a shaft in the other in a raise the deaths in the latter case being however practically on the tunnel level compressed air constituted the usual method for removal of dangerous gases and in both cases it failed 0 in both cases there is at present no obtainable evidence of defectiveness of explosive or of method of firing hence the situations are practically such as may be encountered at any of our operating metal mines especially those operating on a small basis and the question arises as to possible prevention of such occurrences these two disasters are recent and the loss of life makes them of serious concern yet the situation brought out is one which confronts nearly all metal mines in the country large and small the bureau of mines has been asked to attack altac k the problem from various points of view some companies having several mines and employing hundreds of men have numerous cases of powder gassing annually frequently with fatal results and have asked the assistance of the bureau largely as to the possible finding of methods of firing of explosives so that no poisonous fumes will be developed others wish experimental work along the line of developing a foolproof fool proof explosive such that practically irrespective of method of handling surrounding conditions etc no dangerous fumes may be found and still others realizing the probability that dangerous fumes will be generated irrespective of present day available precautions wish information as to positive methods of handling dangerous fumes with the idea of their removal hard to eliminate dangerous gases theoretically there are in existence today explosives with constituents chemically balanced such that with complete detonation there should be no resultant gases of 0 more potential danger than CO which mixed with the almost invariably larger quantities of ordinary air present would be diluted to such an extent as to be practically harm less the bureau of mines has in several publications notably in bulletins 48 and 57 and technical paper 17 given data as to proper methods of blasting selection of explosives plo etc however numerous air samples at blasting faces in metal mines almot almost invariably reveal the presence of dangerous gases due generally to incomplete combustion these dangerous gases being usually CO and oxides of nitrogen dangerous percentages cen upwards of 1 per cent of CO have been obtained at drift faces in matal mines after blasting with explosives of ammonium nitrate as well as gelatin base detonated with number 7 as well as with number 6 caps fired electrically as well as by fuse ramped tamped and the most dangerous gas found in fumes of explosives is CO of which quantities up to and over 1 per cent are frequently found in the general air around newly blasted faces in metal mines and frequently as much as two or three tenths of one per aper cent in air from muck piles several hours after blasting this gas gives headache in air with proportions as low as per cent and is dangerous at 02 per cent and quickly fatal when over per cent another gas sometimes found is nitrous oxide and its eff effect act while serious is not likely to be so quickly fatal as that of CO however when dynamite burns instead of exploding the nitrous oxide content of surrounding air death to may be sufficiently high to cause those breathing it other dangerous gases be found fauna such as HS SO etc may also in i in explosive ve fumes but rarely present however st straight raigh W harmful proportions off offs sev gives explosive dynamite tro glycerine or as 9 gelatin elatin CO gas eral times as much straight hence stra ammonium base explosive the used in nitroglycerine should never be found in mining confined places there at least at present it appears that metal In ining to is no explosive applicable forda that in which there is any guarantee prevented can be pr tion of dangerous gases pre feasible asiDie fe one in blasting hence the bentive is effective ventilation is urged urge mechanical ventilation great eat the 1 1919 it is significant that in states the unite united of coal mining industry tite attea minu inin which is compelled to give deaths but three tion to ventilation had es from suffocation from explosive e though over men were bulletin see U S bureau of mines gas as edip or about three times as many only too metal mines in our metal mines on natural frequently place entire reliance and both air al compressed gna and ventilation or on rous ballge inefficient are likely to be in the long run costly rarey y dea 1 will ivil to 0 o compressed air blower than J face more cob liver to a working tile air pe per x god cubic feet of 1000 cu abc feet is two to five cents per there is danger that at least occasionally tile the compressed coni pressed air may through defective d compressing system be charged with dangerous gases ordinary ventilation methods by mechanical fans produce air circulation at a cost of about two to five cents per 1000 1000 cubic feet and with proper supervision will readily deliver several thousand cubic feet of air per minute to working faces instead of the or thereabouts cubic feet per minute by compressed air blowers for dead end faces of drifts crosscuts cross cuts raises dinzes and shafts small electrically driven fans direct connected to one half to ten H P motors force air through canvas tubing or galvanized pipe and readily deliver 1000 to or more cubic feet of air per minute or ten to fifty times as much air as can be obtained from compressed air blowers and at much less cost these small fan and canvas pipe or galvanized pipe units not only remove explosive fumes from the face but if operated as blowers will keep a stream of moving air at point where the machine man or works and in hot mines especially the workers comfort and efficiency are greatly improved and his health and safety assured at least as far as explosives fumes are concerned larger metal mines now recognize this as and many new mechanical ventilation installations in large metal mines are found especially in the west and the time will soon be at hand when laws will demand efficient mechanical ventilation of metal mines as well as of coal mines efficient ventilation consisting essentially of providing circulation of ample currents of fresh air at all places where men work underground |
