(a) The amount of oxygen supplied by the apparatus must meet the needs of the wearer at all times during these tests.

(b) The regenerating material shall absorb from the expired air carbon dioxide to the extent that not more than 22 percent shall at any time be present in the inspired air. The average shall not exceed 1 percent for the duration of the test period. This average is to be determined by analyses of air samples taken as near the point of inspiration as practicable and at uniform intervals of time. (c) The apparatus shall be sufficiently free from mechanical obstructions for the wearer to breathe freely at all times.

(d) The temperature of the inspired air must not exceed a maximum of 110° F. when that of the external air does not exceed 85° F. A much lower temperature than 110° F. for the inspired air is desirable. Temperature readings will be taken at regular intervals.

(e) The apparatus shall be sufficiently durable in construction and all vital parts so protected as to prevent material damage or wear to the apparatus during the tests to which it will be subjected.**

11.5 Construction. (a) When worn in irrespirable air the apparatus shall, without recharging, meet the needs of the wearer for not less than the period for which it has been designed. The apparatus shall be of a design using a mouth-breathing device or other face attachment that, when properly adjusted to the face of the wearer, has a capacity of not more than 250 cm.3 of dead space inside the face attachment or mouth-breathing device, exclusive of tubes or connections attached thereto.

Preferably, an apparatus shall not weigh more than 36 pounds complete with headpiece and fully charged, and no apparatus weighing more than 40 pounds, complete with headpiece and fully charged, will be accepted for final test.

(b) The mechanical construction of the apparatus shall be such that every part can be tested, inspected, and repaired by persons skilled in such work, and all parts which require sterilizing shall be readily accessible for this purpose.

(c) All parts of the apparatus subject to or liable to be subjected to pressures in excess of 5 pounds per square inch shall be of such construction or equipped with such safety devices as shall insure the safety of the wearer, as determined by the 15 tests hereinafter described.

(d) In apparatus equipped with breathing bag or bags, or their equivalent, the inhalation and exhalation compartments shall have a combined capacity of at least 8 liters. If a single breathing bag is used it shall have a capacity of at least 5 liters.

(e) When the breathing bag is used in conjunction with the operation of the oxygen admission valve the bag shall have capacity for at least 3 liters of air above the closing-off point of the admission valve, and after 3 liters of air is introduced in the bag the watergage pressure shall not exceed 3 inches.

(f) The breathing bag shall consist of material that will exclude mine gases and be impervious to gasoline fumes for at least a 21/2hour period; the material shall be of good strength and flexible, and the seams shall either be cemented and sewed or vulcanized or bound

**For statutory and source citations, see note to § 11.0.

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in such manner that the bag will not come apart at the seams under wearing conditions; or the bag may be made of one piece.

(g) The apparatus shall not have in its circulating system any zone of constant negative pressure, or a positive pressure at the mouthpiece of more than 3 inches water gage after a 22-liter exhalation.

(h) The apparatus shall be provided with a release valve, operated by hand or automatically placed at some point in the circulatory system of the apparatus. The function of this valve shall be to permit the escape to the outside air of a part of the air in the circulatory system of the machine. The valve shall be so designed that no outside air can be drawn into the apparatus on inhalation.

(i) Where apparatus is equipped with high-pressure oxygen cylinders, the applicant submitting the apparatus to the Bureau of Mines for test shall furnish therewith a certificate of test issued by the Interstate Commerce Commission under specifications No. 3-A or shall submit evidence satisfactory to the Bureau's engineer in charge of testing the apparatus that such oxygen cylinders have been tested in accordance with Interstate Commerce Commission Specifications No. 3-A.

(j) In apparatus equipped with high-pressure oxygen cylinders the safety cap attached to the closing valve, in addition to the usual copper disk provided, shall be filled with a metal (such as Rose's metal) fusing at a temperature of approximately 94° C. Such fusible metal shall not extrude from the safety cap under a pressure of 150 atmospheres.

(k) The closing valve of such oxygen cylinders shall be provided with the necessary device to prevent the wearer of the apparatus from screwing the stem entirely out of the valve. The closing valve shall also be provided with a device that will enable the wearer to lock the valve stem open when the valve has been opened to the desired point. The valve-closing device shall be operable by hand and without intervention of wrenches or external levers.

(1) When apparatus is equipped with gages for recording time or pressure of oxygen supply, such gages will be tested for accuracy of calibration by the Bureau of Mines. A variation of 3 atmospheres will be allowed in comparison with the Bureau of Mines standard pressure gage.

(m) The apparatus shall be supplied with a valve to cut off the oxygen supply from the gage; this valve shall be so placed that it can be manipulated readily by the wearer by hand and at the same time not interfere with the flow of oxygen from the oxygen container to the circulatory system of the apparatus.

(n) The gage shall be placed on the apparatus at a point where it can be read easily by the wearer.

(0) Apparatus equipped with a reducing valve giving a constant or automatic flow of oxygen shall be provided with a bypass valve which will permit a free flow of oxygen from the oxygen container to the circulatory system of the apparatus independent of the reducing valve.

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(p) When the oxygen supply of the apparatus is controlled by automatic devices, such devices shall readily adjust themselves to the needs of the wearer.

(q) An apparatus equipped with mouth-breathing device shall be provided with an adequate saliva trap so designed that during the operation of the saliva trap no surrounding atmosphere can be drawn into the apparatus during inhalation. The adequacy of the saliva trap will be determined by the tests to which the apparatus will be subjected.

(r) An apparatus equipped with mouth-breathing attachment shall be provided with a suitable nose clip properly attached to the apparatus. The suitability of the nose clip will be determined by the tests to which the apparatus will be subjected.**

CROSS REFERENCES: For requirement of retest of cylinders, see 49 CFR 80.174 (j). For Interstate Commerce Commission regulations prescribing requirements for shipping containers, Specification 3-A, see 49 CFR 72.3A-1 to 72.3A–8.

11.6 Character and general description of tests. After the self-contained oxygen breathing apparatus under test for permissibility has been thoroughly inspected for mechanical principles, a series of 15 working tests each for a period of time according to the type of apparatus (A, B, C, or D) submitted for testing will be made. At the beginning of the series of tests, if an oxygen bottle is used on the apparatus it shall first be charged with oxygen to a pressure of 10 atmospheres and the oxygen permitted to escape into the air. The bottle used in the tests shall be fully charged at the beginning of each test at a pressure prescribed by the manufacturer of the apparatus. At the beginning of each test the breathing bag or bags shall be deflated to expel any nitrogen contained therein.

A single test must be continuous, without removal of the apparatus from the wearer during the test.

Samples of air will be obtained from the apparatus on the inhalation side of the circulatory system and as near to the mouthpiece or the face attachment as possible. The first sample will be taken from the oxygen bottle to be used and just prior to the beginning of the test. The second sample will be taken immediately after the apparatus has been adjusted to the wearer and oxygen has been turned on. Samples will be taken every 10, 15, 20, or 30 minutes thereafter for 1/2-hour (A) types, 4-hour (B) types, 1-hour (C) types, and 2-hour (D) types, respectively, every half hour thereafter during the test. The physiological effects of the apparatus on the wearer will be noted in each test.

Not more than one test of 2 hours' duration will be made on any one day. The tests will be completed within 60 days from the date of beginning, unless prevented by conditions which are beyond the control of the engineer in charge of the tests.

All tests of apparatus will be conducted in a specially equipped gallery filled with an irrespirable atmosphere, at the Pittsburgh Experiment Station of the Bureau of Mines.

Before beginning each test the apparatus shall be examined and tested to insure that there is no air leakage under working conditions.

**For statutory and source citations, see note to § 11.0.

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The apparatus under test will be worn during each and all of the periods of the 15 tests by the Bureau of Mines engineer in charge of the testing or by one or more of his assistants. Immediately before participation in any of these tests the prospective wearer of the apparatus under test shall pass in a satisfactory manner a physical examination by a qualified physician. If it is impossible to carry any one of these tests to completion solely on account of the poor physical condition of the wearer, where such condition has been brought about through no fault of the apparatus under test, such test shall be disregarded and the apparatus under test shall not be penalized or disqualified thereby.

At the conclusion of each test a note shall be made of the general physical condition of the wearer and of the apparatus and the amount of oxygen, if any, remaining in the container. The schedule of work to be performed by the wearer of the apparatus in each of the 15 working tests is as stated in § 11.7.**

11.7 Detailed procedure of tests. The tests used are designed to represent conditions and work to which the wearer of a selfcontained oxygen breathing apparatus may be subjected while wearing apparatus under actual conditions in a mine or plant.

The distances specified for walking, running, crawling, and carrying material, with the exception of carrying over the overcast, are to be over a level, measured course free from obstructions.

(a) Test 1. The wearer of the apparatus shall walk continuously at a rate of not less than 32 miles per hour for the 12-hour, 34-hour, 1-hour, or 2-hour period, according to the type of apparatus being tested, except for time necessary to take air samples and temperature readings. At the end of each 10-minute period for the 2-hour (A)-type, 15-minute period for the 34-hour (B)-type, 20-minute period for the 1-hour (C)-type, and 30-minute period for the 2-hour (D)-type apparatus 2 minutes shall be allowed for taking air samples and temperature readings.

(b) Tests 2, 3, and 4. These tests will be repetitions of test 1. (c) Test 5. The wearer of the apparatus shall:

(1) Walk, at a rate of not less than 3 miles per hour, for 3 minutes with 12-hour (A)-type, 4 minutes with 3/4-hour (B)-type, 6 minutes with 1-hour (C) -type, and 10 minutes with 2-hour (D)-type apparatus.

(2) Carry a sack of bricks weighing 50 pounds over an overcast, making one complete trip every 2 minutes, 2 times with 1/2-hour (A)type, 3 times with 3/4-hour (B)-type, 4 times with 1-hour (C)-type, and 5 times with 2-hour (D)-type apparatus.

(3) Walk at the rate of not less than 3 miles per hour, for 3 minutes with 12-hour (A)-type, 5 minutes with 3/4-hour (B)-type, 6 minutes with 1-hour (C)-type, and 10 minutes with 2-hour (D)-type apparatus.

(4) Allow 2 minutes for taking air samples and temperature readings.

(5) Carry a 45-pound weight a distance of 400 feet with 1/2-hour (A)-type, 600 feet with 3⁄44-hour (B)-type, 800 feet with 1-hour (C)

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**For statutory and source citations, see note to § 11.0.

type, and 1,600 feet with 2-hour (D)-type apparatus, consuming while doing this work 2 minutes with the 1/2-hour (A)-type, 3 minutes with 34-hour (B)-type, 4 minutes with 1-hour (C)-type, and 8 minutes with 2-hour (D)-type apparatus.

(6) Raise a 45-pound weight a vertical distance of 5 feet, 30 times with 12-hour (A)-type, 45 times with 34-hour (B)-type, 60 times with 1-hour (C)-type, and 75 times with 2-hour (D)-type apparatus, consuming while doing this work 2 minutes with 12-hour (A)-type, 3 minutes with 34-hour (B)-type, 4 minutes with 1-hour (C)-type, and 5 minutes with 2-hour (D)-type apparatus.

(7) Saw wood for 4 minutes with 12-hour (A)-type, 7 minutes with 4-hour (B)-type, 10 minutes with 1-hour (C)-type, and 15 minutes with 2-hour (D)-type apparatus.

(8) Allow 2 minutes for taking air samples and temperature readings.

(9) Carry a sack of bricks weighing 50 pounds over an overcast, making one complete trip every 2 minutes, 3 times with 1/2hour (A)-type, 4 times with 3/4-hour (B)-type, 5 times with 1-hour (C)-type, and 10 times with 2-hour (D)-type apparatus.

(10) Walk, at the rate of not less than 3 miles per hour, for 2 minutes with 12-hour (A)-type, 5 minutes with 34-hour (B)-type, 8 minutes with 1-hour (C)-type, and 8 minutes with 2-hour (D)-type apparatus, taking an air sample and temperature readings at end of 1/2-hour (A)-type, 34-hour (B)-type, and 1-hour (C)-type apparatus tests, and allowing 2 minutes for same purpose with 2-hour (D)type tests.

(11) Continue test with 2-hour (D)-type apparatus by walking 28 minutes at a rate of not less than 3 miles per hour, taking an air sample and temperature readings at end of test.

(d) Tests 6, 7, and 8. These tests will be repetitions of test 5. (e) Test 9. In test 9 the wearer of the apparatus shall—

(1) Walk, at a rate of not less than 3 miles per hour, for 2 minutes with 1/2-hour (A)-type, 3 minutes with 3/4-hour (B)-type, 4 minutes with 1-hour (C)-type, and 5 minutes with 2-hour (D)-type apparatus.

(2) Crawl for a distance of 40 feet with 1/2-hour (A)-type, 60 feet with 34-hour (B)-type, 80 feet with 1-hour (C) type, and 100 feet with 2-hour (D)-type apparatus, consuming while doing this 5 minutes with 12-hour (A)-type, 6 minutes with 34-hour (B)-type, 8 minutes with 1-hour (C) type, and 10 minutes with 2-hour (D)type apparatus.

(3) Lie down on side for 2 minutes with 12-hour (A)-type, 4 minutes with 34-hour (B)-type, 5 minutes with 1-hour (C) -type, and 10 minutes with 2-hour (D)-type apparatus.

(4) Lie down on back for 1 minute with 12-hour (A)-type, 2 minutes with 34-hour (B) -type, 3 minutes with 1-hour (C)-type, and 5 minutes with 2-hour (D)-type apparatus.

(5) Allow 2 minutes for taking air samples and temperature readings.

(6) Walk, at the rate of not less than 3 miles per hour, for 4 minutes with 2-hour (A)-type, 6 minutes with 34-hour (B)-type,

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