To check these observations, a second exploration trip was made. No. 2 crew went to the face of No. 16 butt and No. 3 crew to between rooms 8 and 9 in No. 15 butt. No. 1 crew acted as reserve. Similar observations and reports were made. A sample taken at the seal of No. 16 butt on March 11 showed 2.9 per cent of CO2, 0.1 per cent of O2, 0.1 per cent of CO, 88.8 per cent of CH1, and 8.1 per cent of N2, and with this favorable analysis it was decided to reventilate the area. A line brattice was extended through the crosscut outby the seals in Nos. 15 and 16 butts, and the seal in No. 16 butt was opened by a rescue crew. The doors in the air locks in No. 15 butt were then opened and the fire gases removed as quickly as possible. The rescue crews then entered the area and removed the standing fire gases in the rooms off No. 15 butt. OUTSTANDING FACTORS IN SUCCESSFUL UNSEALING OF HORNING FIRE AREA Twelve crews of five men each, wearing oxygen breathing apparatus, built all air locks and stoppings used in recovering the bodies. In addition they made exploration trips and carried all bodies to the fresh-air base. Three crews were later used in unsealing the final block on March 13, 1926. No long trips were attempted at any time; 300 to 400 feet was the maximum distance the crews traveled or worked ahead of fresh air. All of the crews engaged in the operation did exceptionally good work, and too much can not be said for their training, obedience, willingness, endurance, and courage. The entire project was carried on without injury to any one and with but little apparatus difficulty. A large measure of this can be attributed to a well-planned, well-organized, and wellconducted procedure which was drawn up before the work was started, followed by strict adherence to the plan as outlined. The air sampling and analysis, which showed the condition behind the stoppings at all times, were important factors in the successful conclusion of the work. The type of men composing the apparatus crews and the men in charge of the different shifts also aided materially in the successful completion of the task. Air locks were also employed to unseal mine fires at the Sunnyside mine of the Utah Fuel Co., Sunnyside, Utah, in 1920; the Rockwood mine of the Roane Coal & Iron Co., Rockwood, Tenn., in 1925; the Connellsville No. 1 mine of the Connellsville By-Product Coal Co., Pursglove, W. Va., in 1927; and the Woodward mine of the Glen Alden Coal Co., Edwardsville, Pa., in 1927. RECOVERING A SEALED AREA BY DIRECT VENTILATION When a decision has been made to recover a sealed area by direct ventilation, an air lock should preferably be constructed near the intake seal. A rescue crew using a life line and fully equipped for the work at hand should break the seal, enter, observe conditions, take temperature readings and air samples, and return to the freshair base. If the observations and examination of the affected region have shown that conditions are favorable, the return seal should be broken by an apparatus crew; the air lock should then be opened to admit air. The area should be ventilated, but the combustible gases in the main return should, if feasible, be kept below the lowest. explosive limit. The unsealing of the final fire area of the Horning mine on March 13, 1926, is a good example of unsealing by direct ventilation. If this method of recovering a fire area is employed, it is advisable that all men be out of the mine before the air is actually directed into the sealed area. Some automatic arrangement should be employed which would give ample time for all persons to reach the surface before the fire gases are actually moved. A reasonable period should be allowed for the gases to be removed, and frequent determinations should be made of the return air from the mine; the time for any person to enter should be governed by the quality of the return air. This may be tested by installing a continuous methane recorder in the main return from the mine or by systematic periodic sampling and analyzing. If the workings under seal are extensive it will probably be advisable for crews equipped with oxygen breathing apparatus or possibly with gas masks to reenter the mine and completely clear any standing fire gases out of the fire area. PROCEDURE AT EXPLOSIONS An efficient organization and proper equipment and materials are of prime importance in conducting recovery operations safely after a mine explosion. Improper procedure may sacrifice all possible chance of rescuing any persons left alive in the mine after an explosion and may also result in loss of life among persons doing recovery work. If ventilating fans or appliances have been damaged, wrecked, or destroyed by the explosion, immediate attention should be given to repairs or to providing new equipment necessary for reestablishing the ventilating current. Advantage should be taken of any natural ventilation that has become established to enter the mine and form an idea of existing conditions. As soon as possible all mine openings should be roped off and guarded, a system for checking the men into and out of the mine established, and electric current cut off from the mine. Rescue and recovery crews, necessary equipment, and material should be assembled. The officials in charge of the shift should check over the crews before going underground (fig. 20) to see that everyone is properly equipped for the work at hand. On entering the mine recovery crews should advance in fresh air to the point where ventilation has been destroyed and establish a fresh-air base. A portable telephone (a permissible type should be used if available) should be installed at this point and communication established to the outside. As As recovery work progresses the necessary telephones and wires should be kept near the recovery crews. Telephones should not be installed or left where they are likely to come in contact with explosive gas. fully After a fresh-air base has been established explorations should be made ahead of the fresh air by gas-mask or oxygen breathing-apparatus crews to look for fires and bodies and observe conditions. It is always advisable to make short trips ahead of fresh air (about 250 or 300 feet) rather than long and dangerous trips. Experience has shown that more can be accomplished and the work carried on more safely by this method than by trips far in advance of fresh air. Long explorations should not be made unless they are absolutely necessary to save life or to do other work essential to the continuance of recovery operations. The work ahead of fresh air may be largely performed by gas-mask crews when conditions are such that the masks can be used safely. The oxygen breathing-apparatus crews should be held in reserve for support to the gas-mask crews or for use where gas masks can not be worn safely. When gas-mask or oxygen breathing-apparatus crews are working ahead of fresh air, there should always be another oxygen breathing-apparatus crew, equipped, with their apparatus adequately charged and in good condition, in reserve at the fresh-air base. (Fig. 21.) Before making an exploration the crew about to explore should examine apparatus, life lines, and other equipment to ascertain that everything is in good condition. The crew should be given definite instructions by the man in charge of the operations as to the extent of the trip, distance to travel, things to observe, and time to be taken. Members of the recovery crews who are not equipped with protective devices should not be allowed to go ahead of fresh air so that they breathe the afterdamp, as their efficiency will be reduced and they may be overcome. If no fires are found after exploring ahead of fresh air for some distance, possibly several break-throughs or crosscuts, to ascertain conditions, the next step is to erect the necessary temporary stoppings to ventilate the explored section. The fresh-air base is then advanced approximately to the end of the traveling air. This procedure of alternately exploring and advancing the air should be continued until the entire mine or affected area is recovered. Smoldering or sometimes active fires are frequently found after explosions. These are extremely dangerous, and unless proper precau tions are taken explosive gas may be ignited, causing another explosion. Safe practice requires that ventilation be kept under complete control at all times and that no air be allowed to travel over unex plored territory. If fires are found while exploring they should be extinguished by the rescue crews with water, rock dust, fire extinguishers, etc., before the fresh air is advanced to the fire. Where a FIGURE 20.-Oxygen breathing-apparatus crew, gas-mask men, and officials in charge of shift at an actual mine explosion |