ing through the last open crosscuts of entries, and the volume of air in each split. A record of these measurements shall be kept in a book on the surface and shall be open for inspection by interested persons.

SEC. 4. Coursing of air.-a. The main-intake and main-return air currents in slope mines driven after the effective date of thic code shall be in separate openings. The main-intake and main-return air currents in a single shaft sunk after the effective date of this code shall be separated by a curtain wall or partition substantially constructed of fireproof material.

b. Underground stables, battery-charging stations, and transformer stations containing liquid-filled transformers shall be well ventilated by separate splits of air conducted through vents to the return air courses and returning direct to the surface.

c. Changes in ventilation that may affect the safety of the men shall be made when the mine is idle and with no men in the mine, other than those engaged in changing the ventilation.

SEC. 5. Quality of air.-a. Air in which men work or travel in mines shall be improved when it contains less than 19.5 percent oxygen, more than 0.5 percent carbon dioxide, or is contaminated with noxious or poisonous gases.

b. If the air immediately returning from a split that ventilates any group of active workings contains more than 1.0 percent methane, as determined with a permissible flame safety lamp, by air analysis, or by other recognized means of accurate detection, the ventilation shall be improved.

c. If the air immediately returning from a split contains 1.5 percent methane, the employees shall be withdrawn from the mine or portion of the mine affected, and all power shall be cut off from said mine or portion of the mine until such dangerous condition has been corrected: Provided, however, That in virgin territory in those mines ventilated by exhaust fans, where methane is liberated in large amounts and a large volume of air is provided (double or more than the minimum requirements contained in section 3c of this article), the methane content in a split may exceed 1.5 percent but shall not exceed 2.0 percent: Provided further, That only permissible electric equipment is used, that the air does not pass over trolley or other bare power wires, and that a certified official is continually testing the gas content of the air during mining operations.

d. At working faces and other places where methane has accumulated and is likely to attain an explosive mixture, blasting shall not be done and the men shall be removed from such working faces or places until such condition has been corrected.

e. When the methane content of air in face operations exceeds 1 percent at any point not less than 12 inches from the roof, face, or rib, as determined by a permissible methane detector, a permissible flame safety lamp, or chemical analysis, this condition shall be corrected by improving the ventilation promptly.

SEC. 6. Crosscuts and stoppings.-a. Crosscuts between entries and rooms shall be made at intervals consistent with practice in the States where mine operations are conducted.

b. Crosscuts between entries shall be closed, except the last one in a pair or set of entries.

c. Where necessary to obtain a movement of air to the face of a room to clear the room of flammable or noxious gases, crosscuts between rooms shall be closed, except the one nearest the face.

d. Where practicable, a crosscut shall be provided at or near the face of each entry or room before the place is abandoned.

e. Entries, rooms, or chutes shall not be turned off an entry beyond the last crosscut. This does not apply to the driving of such places to make a connection at the first crosscut or similar passageway used as a main airway in connection with an entry. It does apply to extending such places beyond the airway before the main intake and return passageways are connected.

f. On entries other than room entries, stoppings in crosscuts between intake and return airways shall be built of solid, substantial, incombustible material, such as concrete, concrete blocks, brick, or tile. In mines where physical conditions exist because of heavy or caving ground so as to make the use of concrete, concrete blocks, brick, or tile impracticable, timbers laid longitudinally "skin to skin" may be used.

SEC. 7. Doors and overcasts.-a. Doors used on main-entry or cross-entry (entries from which room entries are turned) haulage roads, which when open would connect intake and return air courses ventilating the mine inby such doors, shall be built to allow minimum leakage of air and shall be in pairs to provide an air lock large enough to contain an entire trip: Provided, however,

When only a single door is installed, such single door shall be attended except in the case of panel or room entries in process of development. Where airlock doors are provided, there shall be sufficient leakage to prevent accumulations of methane between the doors.

b. Doors shall be kept closed except when men or equipment is passing through the doorways. Motor crews and other persons who open doors shall see that the doors are closed before leaving them.

c. Overcasts shall be constructed tightly of incombustible material, such as masonry, concrete, concrete blocks, or prefabricated metal, of sufficient strength to withstand possible falls from the roof, and be of ample area to pass the required quantity of air.

SEC. 8. Line brattice.-a. Substantially constructed line brattice shall be used from the last open crosscut of an entry or room, when necessary to remove gases, explosives fumes, and smoke. When damaged by falls or otherwise they shall be repaired promptly.

b. The space between the line brattice and the rib shall be large enough to permit the flow of a sufficient volume of air to keep the working face clear of flammable and noxious gases.

c. Flame-resistive brattice cloth shall be used in the construction of line brattice.

SEC. 9. Old workings.—a. Abandoned workings shall be posted to warn unauthorized persons against entering the territory.

b. Abandoned workings shall be sealed or ventilated. The sealing or ventilating of abandoned workings shall be governed by the law or practice in the State where the mine is operated.

c. Where practice is to seal abandoned workings, the sealing shall be done in a substantial manner with incombustible material. In every sealed area, one or more of the seals shall be fitted with a pipe and cap or valve to permit the gases behind the seals to be sampled and also to provide a means of determining any existing hydrostatic pressure.

d. Air that has passed through abandoned sections or that has been used to ventilate pillar lines shall not be reused to ventilate live workings. Mines that cannot comply with this requirement may continue to operate as at present until future mine development and ventilation can be changed to permit compliance with this section. (See article V, section 10a.)

SEC. 10. Examinations for gas and dangerous conditions.-a. Any mine in which methane has been ignited or has been found by a permissible flame safety lamp or by air analysis in an amount of 0.25 percent or more in any open workings shall be operated in full compliance with this code. However, a mine in which methane has not been detected shall be exempted from compliance with the following provisions or the part thereof indicated:

Article IV, section 5a7.

Article V, sections 1d; 1g; 2b; 2c1 (Permissible driving unit only); 2c4;
9d; 10c; 10j (Gas and oxygen testing only); and 10k (Gas testing only).
Article VII, section 6d (Except open-flame trip lights shall not be used).
Article VIII, sections 9a; 9c; 9d; 9f (Gas.testing only); and 9h.
Article XI, sections 5a; 6a; 6b (Gas testing only).

Article XII, sections 1c (Permissible cap lamp and flash lamp only).
The exemptions from compliance hereinbefore provided for shall continue
until the presence of gas in the mine has been verified by the United States
Bureau of Mines and the operating manger advised therof.

b. Not less than two permissible flame safety lamps in proper working condition shall be kept available at each mine for the use of authorized persons. Only permissible flame safety lamps, methane detectors, or air sampling and analysis shall be used for determining the presence of methane in mine air.

c. Mine officials whose regular duties require them to inspect working places shall have in their possession, when underground, a permissible flame safety lamp in safe working condition, for the detection of methane and oxygen deficiency. (See article V, section 10a.)

d. Fire bosses or mine examiners shall make examinations of all mines before other men are permitted to enter, and they shall begin their examination in the first working place in their assigned territory not more than 4 hours before the first shift enters the mine; however, such examinations in multiple-shift operations may be made by certified officials or other competent persons designated by the mine foreman or mine manager within 4 hours of the entrance of the next or succeeding shift, provided that in mines in which gas has not been found such examination need be made only once in 24 hours.

e. The duties of the fire boss or mine examiner shall be to visit every live working place in the mine; test with a permissible flame safety lamp for accumulations of methane, noxious gases, and oxygen deficiency; examine seals and doors; test and inspect the roof, face, and rib conditions on active roadways and travelways, approaches to abandoned workings, and accessible falls in active sections for explosive gas and other hazards; be certain that the air is traveling in its regular course in each split; and place his initials and the date at or near the face of each place examined.

f. Where dangerous conditions are found by the fire boss or mine examiner (or other official), the place shall be marked out with a DANGER sign and no one except an authorized person shall cross the DANGER sign, and then only for the purpose of correcting the dangerous condition.

g. Upon completion of his examination, the fire boss or mine examiner shall report to a proper official on the surface or report at a designated underground station any defects found before the men enter the mine or pass such designated station.

h. The fire boss or mine examiner shall record in ink or indelible pencil the result of his inspection in a book kept on the surface for that purpose. Similar records may also be kept at designated stations underground.

i. Idle and abandoned sections shall be inspected for gas and other dangerous conditions by a certified foreman or fire boss immediately before other employees are permitted to enter or work in such places.

j. At least once during each shift while the men are in the mine, or oftener if necessary for safety, the mine manager or mine foreman, his designated assistants, or other designated competent persons, shall examine all working places with a permissible flame safety lamp for methane, noxious gases, oxygen deficiency, and other hazards. Any dangerous condition found shall be corrected promptly. (See article V, section 10a.)

k. Pillar workings shall be examined for explosive gas and other dangers before a fall is made. If methane is found in amounts that can be detected with a permissible flame safety lamp, the fall shall not be made until the gas is removed or other precautions taken to safeguard all employees. (See article V, section 10a.)

1. At least once each week, air samples shall be collected for analysis, or tests for methane shall be made in all mines with a permissible methane indicator or a permissible flame safety lamp by the mine foreman or mine manager or other competent person designated by him, in the return of each split immediately out by the last working place, in the main return, pillar falls, seals, abandoned workings, and entrances thereto, who shall also make an examination for other dangerous conditions; leave his initials and date at the places examined; and, if dangerous conditions are found, they shall be corrected promptly. A record of these tests and examinations shall be kept.

m. The mine foreman or mine manager shall read and countersign the record book of the fire bosses or mine examiners daily and read and countersign the daily and weekly reports of assistant mine foremen, or where existing State laws require other procedure, such signing shall be done in accordance with prevailing practice. Where such reports disclose any dangerous conditions, prompt action shall be taken to have them corrected. The superintendent or official in charge of the mine shall also read and countersign the daily and weekly reports of mine officials.

n. All records of daily and weekly reports shall be open for inspection by interested persons.

ARTICLE VI-COAL AND ROCK DUST

SECTION 1. Control of coal dust.-a. Coal dust shall not be permitted to accumulate excessively on roadways and along conveyor lines.

b. When mining operations raise an excessive amount of dust into the air, water or water with a wetting agent added to it or other effective methods shall be used to allay such dust at its source.

SEC. 2. Rock dusting.-a. All mines, except those mines or those locations in a mine which are too wet or too high in incombustible content to propagate an explosion, shall be rock-dusted to within 80 feet of the faces of rooms and entries; however, if the mine or any part of it is wet but becomes dry, the mine or portion of the mine so affected shall be rock-dusted as soon as it becomes dry. b. In mines partially rock-dusted or in mines that are required to start rock dusting, haulageways and parallel entries connected thereto by open crosscuts shall be rock-dusted. Back entries shall be rock-dusted for at least 1,000 feet

outby the junction with the first active entry. Inby this junction, the rooms, entries, and crosscuts shall be rock-dusted by generalized rock dusting as proIvided for in section 2a.

c. Where rock dust is applied, it shall be distributed upon the top, floor, and sides of all open places and maintained in such quantity that the incombustible content of the mine dust will not be less than 65 percent. In trackless entries and air courses, protection in lieu of generalized rock dusting may be had by using bags filled with rock dust, if they are placed at regular intervals and staggered as described in Bureau of Mines Report of Investigations 3411.

d. When methane is present in any ventilating current, the 65 percent of incombustible matter shall be increased 1 percent for each 0.1 percent methane. e. Pending tests to be conducted at the Experimental mine, variations of the method described in Report of Investigations 3411 may be continued in mines now using or starting to use the bag method. After completion of these tests, the Director of the Bureau of Mines will review the results of the tests and will issue a revision of article VI, section 2.

ARTICLE VII-TRANSPORTATION

SECTION 1. Hoisting.-a. A qualified hoisting engineer shall be on duty continuously when men are underground.

b. Hoists used for handling men shall be equipped with overspeed, overwind, and automatic stop controls, unless a second engineer is on duty.

c. At the beginning of each shift and after the hoist has been idle, the hoisting engineer shall operate the cages up and down the shaft at least one round trip before hoisting or lowering men. Similar procedure shall be followed in slope hoisting, except that an attendant may ride on the trip.

d. Slope, shaft, or incline-plane hoists shall be equipped with brakes capable of stopping and holding the fully loaded unbalanced cage or trip at any point in the shaft, slope, or on the incline.

e. An accurate and reliable indicator, showing the position of the cage or trip, shall be placed so as to be in clear view of the engineer, unless the position of the car or trip is clearly visible to the engineer at all times.

f. Hoisting equipment shall be inspected daily and a record made of such inspection, which shall be open for inspection by interested persons.

g. Hoisting ropes on all cages or trips shall be adequate in size to handle the load and have a proper factor of safety as defined in the American Standards. Association's Wire Rope Standards and shall be replaced when it shows more than six broken wires in any single pitch length or lay of rope.

h. The rope shall have at least three full turns on the drum when extended to its maximum working length and shall make at least one full turn on the drum shaft or around the spoke of the drum (in case of a free drum) and be fastened securely by means of clamps.

i. A hoisting rope shall be fastened to its load by a spelter-filled socket or by a thimble and clamps.

SEC. 2. Cages and shafts.—a. Cages used for hoisting men shall be of substantial construction; with adequate steel bonnets; with enclosed sides; with gates, safety chains, or bars across the ends of the cage when men are being hoisted or lowered; and with sufficient handholds or chains for all men on the cage to maintain their balance.

b. The floor of the cage shall be constructed so that it will be adequate to carry the load and so that it will be impossible for a workman's foot or body to enter any opening in the bottom of the cage.

c. Cages used for handling men shall be equipped with safety catches that act quickly and effectively in an emergency.

d. Cages shall be inspected daily. A test of safety catches on cages shall be made at least every 2 months. A written record shall be kept of inspections and tests, which shall be open for inspection by interested persons.

e. The speed of the cage when hoisting or lowering men, unless regulated by State laws, shall not exceed 900 feet a minute.

f. There shall be at least two independent methods of signaling, one of which shall be audible to the engineer, from all landings in shafts and slopes.

g. An approved signal code shall be in use at each mine and shall be posted prominently in the engine room in easy sight of the engineer and at all places where signals are given.

h. Workmen shall wear safety belts while doing repair work in or over shafts.

i. An attendant shall be on duty at all cage stations when men are being hoisted or lowered at the beginning and end of each operating shift and when men are working in the shaft.

j. Shafts shall be equipped with self-closing or manually controlled safety gates at surface landings.

k. Positive stop blocks or derails shall be placed near shaft surface landings. 7. At the bottom of each hoisting shaft and at intermediate landings, a “runaround" shall be provided for safe passage from one side of the shaft to the other. This passageway shall be not less than 5 feet in height and 3 feet in width.

SEC. 3. Haulage roads.—a. The roadbed, rails, joints, switches, frogs, and other elements of the track of all haulage roads shall be constructed, installed, and maintained in a manner consistent with speed and type of haulage operations being conducted to insure safe operation.

b. Track switches, except room and entry development switches, shall be provided with properly installed throws, bridle bars, and guardrails; switch throws and stands, where possible, shall be placed on the clearance side.

SEC. 4. Clearance and shelter holes.-a. Haulage roads on entries developed after the effective date of this code shall have a continuous unobstructed clearance of at least 24 inches from the farthest projection of moving equipment.

b. On haulage roads where trolley lines are used, the clearance shall be on the side opposite the trolley lines.

c. On the trolley-wire or "tight" side, there shall be sufficient clearance to prevent the farthest projection of moving equipment from rubbing or coming in contact with ribs or timber.

d. After the effective date of this code, all new sidetracks, partings, or entries equipped with more than one track shall have a clearance of at least 24 inches between the outermost projection of moving traffic.

e. The clearance space on all haulage roads on entries driven before or after the effective date of this code shall be kept free of loose rock, coal, supplies, or other materials, provided that not more than 24 inches need be kept free of obstructions.

f. Ample clearance shall be provided at all points where supplies are loaded or unloaded along haulage roads or conveyors.

g. Where it is necessary for men to cross conveyors regularly and where the width of conveyors or low roof introduces a hazard, suitable cross-over bridges shall be provided.

h. Shelter holes shall be provided along haulage entries driven after the effective date of this code where locomotive, rope, animal, or shuttle-car haulage is used. Such shelter holes shall be spaced not more than 80 feet apart. Except where the trolley wire is 6 feet or more above the roadbed or guarded effectively at the shelter holes, they shall be on the side of the entry opposite the trolley wire.

i. Shelter holes made after the effective date of this code shall be at least 5 feet in depth, not more than 4 feet in width, and 6 feet in height or as high as the traveling space, if the traveling space is less than 6 feet high. Room necks and crosscuts may be used as shelter holes even though their width exceeds 4 feet.

j. Shelter holes shall be kept clear of refuse and other obstructions.

k. Shelter holes shall be provided at switch throws, except where more than 6 feet of clearance is maintained and at room switches.

1. At each landing of a slope where men are passing and cars are handled, a shelter hole at least 10 feet deep, 4 feet wide, and 6 feet high shall be provided. SEC. 5. Haulage equipment.—a. Nonpermissible internal-combustion engines or other machinery which gives off noxious fumes shall not be permitted underground in any coal mine.

SEC. 6. Safety devices and practices.-a. Locomotives shall be equipped with proper devices for the rerailing of locomotives and cars.

b. An audible warning device and headlights shall be provided on each locomotive,

c. Where hoists are used for handling men in underground slopes, in pitching beds, or on slopes between two or more beds, the provisions governing hoisting or haulage mentioned heretofore shall apply.

d. A permissible trip light shall be used on the rear of trips pulled, and on the front of trips lowered into slopes or pushed. Trip lights need not be used during gathering operations at working faces. The use of efficient reflectors in lieu of trip lights may be continued where now in use pending an investigation