have lost their lives by neglecting to build barricades. Also, imprisoned miners have built barricades in an imperfect or inadequate way and as a result have perished. A barricade must be gas tight, and the barricaded place must not have any other connection and must not have been gas contaminated before use as a refuge. Investigations after mine explosions have shown that many of the men found dead had escaped the violence and flame of the explosion but had succumbed to the gases, called afterdamp, left by the explosion. The evidence collected shows that in a selected list of 140 mine disasters 1,477 men were killed outright and 1,391 men were overcome by afterdamp. In other words, about 48 per cent of the men killed in these disasters were alive after the explosion occurred and probably died from afterdamp. In some instances miners have traveled long distances from their working places before encountering deadly gases, and groups of men have been found dead in remote sections of mines to which they had retreated to escape the afterdamp. Again, men have been found dead near a pile of brattice material, which they did not use because they probably did not know that a barricade would be of value. In several instances where miners were rescued after an explosion they said that they knew nothing about the erection of barricades, so there are possibly many others unaware of this method of escaping death when left alive in a mine during a fire or after an explosion. When there is a fire or an explosion in a mine, undoubtedly the first impulse of the survivors is to dash for the nearest exit, either to the surface or to the shaft bottom to be hoisted out of the mine. Under circumstances such as these men naturally desire to get out as quickly as possible, but frequently in making their way to the surface they rush into afterdamp or the afterdamp overtakes them and they are overcome. In every crowd there is nearly always at least one cool-headed man who is able to take charge of a number of excited and more or less terror-stricken men, and he should be obeyed for the welfare of all concerned. When miners are trapped by a mine fire or left alive after an explosion, they should not rush aimlessly around but should immediately make an effort to protect themselves. The following recommendations are made as an aid to the proper method of doing this. RECOMMENDATIONS FOR CONSTRUCTION OF BARRICADES 1. When entrapped by gases from mine fires or explosions, keep uppermost the thought of building a barricade or bulkhead and collect tools, timber, canvas, water, dinner buckets, and anything else that might be useful. 2. As soon as possible a suitable place should be chosen for the erection of a barricade and its construction started without delay, as the deadly gases often travel quickly. An efficient barricade can be erected in periods of 30 minutes to 2 hours, depending on conditions. 3. The ventilation should be short-circuited as soon as possible by opening doors or destroying stoppings, and temporary barricades should be erected by hanging brattice cloth or moving a door to a new place across an entry. The permanent barricade should be started about 50 feet from the temporary construction. 4. As much territory as possible, such as entries or drifts, rooms, and crosscuts, should be included in the barricaded area, regardless of the number of men in the party, so as to provide a maximum quantity of air. 5. Before constructing barricades make sure that there are no other openings or connections with other workings through which gases could enter. Also make sure that the entry or drift is not in broken ground or in strata through which gas could find its way. In metal mines back-filled ground should not be chosen, as gases are likely to pass through such regions. 6. If a barricade of lumps of coal, slate, rock, or ore is erected, two walls about 2 to 3 feet apart should be built and the space between filled with fine material, preferably mud. The stoppings must be air-tight. Board stoppings are, as a rule, not as easily made gastight as those erected of dirt or rock and dirt, especially dirt in the form of soft clay or mud. However, board stoppings covered by canvas or damp brattice cloth can be made sufficiently tight to exclude the dangerous gases. 7. All chinks and holes in the barricade should be stopped with clay, rags, clothes, or similar material. 8. Barricades in coal mines should not, if avoidable, be erected in workings or places that give off gas (methane), for fire damp may accumulate and be ignited in some way. Also the accumulations of methane will displace air behind the barricade, and the life-sustaining capacity of the barricaded area will be shortened. 9. If a piece of pipe is available, it should be placed through a stopping of the barricade and plugged at the inner end, so that tests of air outside the barricade can be made. 10. After the barricade has been built the men should keep as quiet as possible, because a man uses several times as much oxygen when he exerts himself as when he keeps absolutely quiet. However, occasionally somebody should walk around so as to mix the air. All the men should not congregate in one place. 11. All flame lamps should be extinguished to conserve oxygen; also, if methane is given off the flame would soon cause an explosion. It is desirable not to use candles, carbide lamps, flame lamps, or electric batteries needlessly. 12. Food and water should be conserved as long as possible. 13. A sign should be placed outside the first stopping, if more than one is built, to show that men are behind it. 14. If possible, barricades or bulkheads should be erected with a valve inclosed in the compressed-air line if compressed air is used in the mine. The valve should be opened when necessary to furnish additional air, precautions being taken, however, not to allow poisonous gases to enter the barricaded region through the compressed-air line after the compressed air fails. 15. It is very important that underground employees should be familiar with all escapeways, manways, and other exits. They should also know which entries serve for intake and return air currents. A mining company should have all parts of a mine equipped with easily read direction signs indicating the pathway to exits. 16. Many lives have been sacrificed because miners did not know the coursing of the ventilation in the particular section of the mine in which they were at work at the time of the explosion or fire. LIFE-SUSTAINING CAPACITY OF BARRICADED CHAMBERS A barricaded area forms a refuge chamber for the men within, and the cubic content of the inclosed space determines the number of men and length of time they can safely remain there. In breathing, the men consume oxygen from the air and give off an almost equal amount of carbon dioxide. When the proportion of carbon dioxide in the air of the inclosed space reaches 8 per cent, the men will breathe heavily and be at the point of complete exhaustion. Actually, men have lived for considerable periods in an atmosphere in which a carbide light would not burn, indicating that the air they breathed had less than 13 per cent of oxygen. A man at rest consumes less oxygen and gives off less carbon dioxide than if he were at work. In a confined space, however, the air will finally become unfit to sustain life. Experiments have shown that a man in a confined space requires approximately 1 cubic yard of air per hour. At the end of an hour this cubic yard of air will contain about 14 per cent of oxygen and 5 per cent of carbon dioxide; an oil lamp will not burn, and an acetylene lamp will be almost extinguished. On the basis of 1 cubic yard of air per hour an inclosed space which is 10 feet wide, 10 feet high, and 10 feet long and contains 1,000 cubic feet or 37 cubic yards of space will support one man for 37 hours before he begins to suffer 20855°-29-2 through lack of breathable air. This minimum allowance of 1 cubic yard per hour per man, however, does not provide for loss of oxygen through absorption by the coal or timber in the inclosed space or for the impairment of the air by methane or carbon dioxide from the coal or rock. In some bituminous coal mines the oxygen behind seals is absorbed so rapidly that in one or two weeks not enough will be left to support life. In a metal mine a barricaded drift 250 feet long, 6 feet high, and 6 feet wide, containing 9,000 cubic feet of air, kept 29 men alive for 36 hours. In the same mine another one 130 feet long, 7 feet high, and 7 feet wide, containing 6,500 cubic feet, supported 6 out of 8 men for 50 hours; the other 2 were found dead. The 6 who were alive were all unconscious but were later revived. VALUE OF BARRICADES The value of barricades can not be emphasized too strongly, as they have been the means of saving hundreds of lives in coal and metal mines, and as many additional lives may be saved if men are properly instructed in their use. The first barricade recorded in the reports of the Bureau of Mines was built by entombed miners during the fire in the Cherry mine, Cherry, Ill. This saved the lives of 20 men, who were rescued 7 days after the erection of the stoppings. Many additional lives in both coal and metal mines have since been saved by the prompt erection of barricades. Table 1 is a list of the barricades erected in coal and metal mines up to January, 1929. TABLE 1.--Summary of barricading incidents by dates TABLE 1.-Summary of barricading incidents by dates-Continued. 1 Add columns 7 and 11 to get total deaths in each mine; columns 10 and 11 together show how many men were behind the barricades. Canvas brattice. Of these 4 were lost after leaving the barricade and were gassed, 2 died from exhaustion behind the barricade, and 19 overlooked an open manway through which gases entered the bulkheaded drift. Only partly built; men waited too long. $1 built and another partly built, but an explosion blew down the first one. Second barricade unfinished; air bad from start. 71 started out from barricade too soon and was found dead; 1 horse saved. * 2 started out from barricade too soon and were found dead; 13 horses saved. BARRICADES IN COAL MINES According to records of the bureau barricades in coal mines have saved a total of 496 lives. This number would undoubtedly be much larger if other miners had made an effort to erect barricades instead of rushing into poisonous atmospheres. The barricades erected will be briefly described according to type. BARRICADES CONSTRUCTED OF BRATTICE CLOTH 1. By bratticing themselves in an emergency shelter hole, closing the sliding door in a stopping above a compressed-air pump, erecting a curtain on the other side of the pump, and then breathing the exhaust from the pump 13 men saved their lives in the San Bois mine at McCurtain, Okla. 2. At the time of the explosion in No. 5 mine at Eccles, W. Va., 74 men were in No. 6 mine above it; of these 8 men were overcome by afterdamp, 31 were rescued, and 35 saved themselves by retreating from the hot afterdamp to a sump room, where they bratticed themselves off with canvas. |