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Type F: Other special gases. Tests similar to those described will be performed on other special gases and will be arranged as the need arises.

Special combination for different types of gases, as above:

Canisters may be tested according to two or more methods, under types A, B, C, D, and E, to obtain approval for different gases classed under the different types.

To meet the approval of the Bureau of Mines the life for gases in each type or class must equal the separate requirements.

Extension of approval may be granted a canister for a warning agent used in conjunction with another gas for which the canister has been approved providing the test most nearly exhausting the life of the approved canister is repeated in duplicate with the warning agent present in the highest amount for which the canister is to be approved.

To meet the approval of the Bureau of Mines the life of the canister for the gas and warning agent mixture must be the same as for the gas alone and the air from the canister during the test must not contain more than 5 parts per million of the warning agent.

Type N: For protection in air against all gases, vapors, and smokes. These canisters are set for protection in air against all substances included in the preceding classes, and in the same degree. The canisters will be tested as described under types A, B, C, D, and E, class 1; or E, class 2. To meet the approval of the Bureau of Mines, it will be necessary that the life for gases in each type or class equal the separate requirements.

(g) Chemical stability tests. To determine the chemical stability under extreme conditions of dryness and moisture, two canisters will be subjected to each of the following tests for which approval is desired:

(1) Air free of carbon dioxide, at a temperature within the range 22° to 26° C. and 25-percent relative humidity, will be passed through each canister at a rate of 64 liters per minute for a period totaling 6 hours. The canisters will be placed in an upright position, kept at a temperature within the above-mentioned range for a period not to exceed 18 hours, and then tested as described under paragraph (f), against gases as follows:

Approval for acid gas: Chlorine.

Approval for organic vapor: Carbon tetrachloride.

Approval for ammonia: Ammonia.

Approval for carbon monoxide: No test.

Approval for special gas: Special gas to be arranged.

Approval for dusts and mists: No test.

Approval for combinations: Any two or more of the above.

To meet approval, the life of the canister must not fall below 10 minutes in any test. The chemical-stability tests may be omitted for canisters designed for carbon monoxide as one of a combination.

(2) Tests as described in (1) of this paragraph to be repeated using the same test conditions except with air containing 85 percent relative humidity. The test gases and requirements are also the same as described in (1).

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(h) High rates of breathing and maximum concentration tests. To insure protection to the wearer at high rates of breathing in gas of high concentration a stream of air containing 1 percent of gas and flowing at a rate of 64 liters per minute will be passed continuously through a canister. The other conditions of the tests will be the following:

Humidity: 50 percent relative humidity.

Temperature: Room temperature (approximately 25° C.).

Gas used in testing:

Approval for acid gas: Phosgene.

Approval for organic vapors: Carbon tetrachloride.

Approval for special gas: Ammonia, carbon monoxide, or other special gas.

Approval for dusts and mists: No test.

Approval for combinations: Any two or more of the above.

Number of canisters: Two, tested against any gas.

To meet the approval of the Bureau of Mines the life of the canisters under any of the above tests against gas must be at least 5 minutes, except for carbon monoxide, which must be at least 15 minutes for class 1; class 2 need not undergo these tests.

(i) Tests required to obtain approval for higher concentrations. The Bureau of Mines requires that a gas mask pass the tests outlined in the preceding sections to obtain approval for use in concentrations of 1 percent of gas, the minimum for which the Bureau will grant approvals. To obtain approval for higher concentrations the canister must pass tests similar in every way to those that have been described, except that in tests described in paragraph (h) of this section the maximum concentration of the gas is used for which approval in higher concentrations than 1 percent is desired. Approvals will be limited to concentrations not exceeding 2 percent of acid gases, organic vapors, carbon monoxide, and 3 percent of ammonia, or 2 percent total of poisonous gases when more than one class is present.

(j) Man-tests. The final criterion for judging a gas mask for permissibility will be the protection afforded by the complete mask when worn by men. The mask shall be capable of giving complete respiratory protection a period of 30 minutes when worn by men breathing the maximum concentration of gas or gases for which the mask is to be approved. When the approval is for concentrations of 1 percent or less of acid gases and 2 percent or less of organic vapors, carbon monoxide, or ammonia, with the exception of hydrocyanic acid gas, the man-tests shall be made by men wearing the mask in a room filled with the gas-laden air. With concentrations higher than the foregoing the men shall wear the mask for 10 minutes in the gasladen air and immediately following shall breathe the gas-laden air through the canister attached to a source of the test atmosphere for 20 minutes. This change in procedure is necessitated by the fact that these high concentrations of ammonia and such acid gases as sulphur dioxide cause marked discomfort through irritation of the skin and even severe blistering if exposure is prolonged. Man-tests with the entire body exposed to hydrocyanic acid gas will be limited to 2 minutes in 2 percent, followed by breathing through the canister (with body unexposed), the concentration for which the device is approved for a duration of 28 minutes. The period for exposure of

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the entire body to hydrocyanic acid gas during man-tests is decreased, owing to the danger of absorbing enough gas through the skin to cause poisoning if exposure is for longer periods. No excessive fogging of the eyeglasses shall take place, or no undue discomfort shall be experienced because of fit or other physical or mechanical features of the gas mask.*+

13.14 Changing detail of tests. If the mechanical or other features of a gas mask render it advisable to omit any of the tests or part of a test previously described, or to perform accessory tests, the Bureau reserves the right to modify the test in such manner as to obtain substantially the same information and degree of safety as is provided by the tests described.**

13.15 Approval letter. After all inspections and tests have been satisfactorily completed and suitable drawings and specifications placed on file, the manufacturer will be given official notification by letter from the Director of the United States Bureau of Mines, Washington, D. C., that his mask has been judged to have met the requirements of this part; he shall then be free to advertise such a gas mask as permissible.

No verbal reports of the Bureau's decisions concerning the investigation will be given, and no informal approvals will be granted.*†

13.16 Wording of approval plate and label. With the approval letter the manufacturer will receive a photograph of a design of an approval plate and any necessary labels. These approval markings shall bear the seal of the Bureau of Mines and be inscribed in effect, as follows:

Permissible gas mask for

not exceeding‒‒‒‒‒‒percent in air.

in concentrations

(Name of gas)

U. S. Bureau of Mines Approval No.‒‒‒‒‒‒
Issued to‒‒‒‒

(Name of manufacturer)

With canister gas masks it is the usual practice to require an approval plate on the container for the complete device and an approval label for the canister. The wording on the approval plate may differ slightly from that on the canister label.

The carbon monoxide gas mask of class 1 should have the inscription:

Use only where flame safety lamp will burn. Self-rescue respirators should have the inscription:

Approved only for self-rescue from carbon monoxide. When deemed necessary, appropriate instruction and caution statements will be included.

The manufacturer shall have this design reproduced on each permissible canister and gas-mask case in any of the ways described in $13.13 (a). The size and position of the approval markings shall be satisfactory to the Bureau.

Should the label not be plainly visible when the canister is attached to the harness for use it may be necessary to attach a similar label to the harness. To be able to identify the approved face pieces the Bureau requires a symbol as "B. M. 1400" stamped or

*For statutory and source citations, see note to § 13.0.

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stenciled on each facepiece in bold, waterproof letters and figures at least three-eighths inch high, placed in a position plainly visible.** 13.17 Purpose of approval plate and label. The approval plate and labels identify the gas mask and/or canister so any one can tell at a glance that they are permissible. By means of the approval plate or label the manufacturer can point out that his gas mask complies with the specifications of the Bureau of Mines and that it has been judged to be safe for use in irrespirable atmospheres under the conditions stated on the approval markings. Permission to place the Bureau's marks of approval on his gas mask obligates a manufacturer to maintain the quality of his product and to see that each gas mask in all its parts is constructed according to the drawings or records that have been accepted by the Bureau for this gas mask and are in the Bureau's files. Gas masks that exhibit changes in design or include any parts that have not been approved are not permissible gas masks and must not bear the Bureau's approval label.**

13.18 Withdrawal of approval. The Bureau reserves the right to rescind for cause any approval granted under this part.**

13.19 Changes in design subsequent to approval. All approvals are granted with the understanding that the manufacturer will make his gas mask according to the drawings or designs submitted to the Bureau and considered and included in the approval. Therefore, when he desires to make any change in the design of a permissible gas mask he should first of all obtain the Bureau's approval of the change. This procedure is as follows:

(a) The manufacturer shall write to the Director of the Bureau of Mines at Washington, D. C., requesting an extension of his original approval and stating the change or changes desired. He should send a copy of the letter, a revised drawing and specification showing the change in detail, and one of each of the gas-mask parts affected, to the Pittsburgh Experiment Station, United States Bureau of Mines, 4800 Forbes Street, marked "Attention of the Supervising Engineer."

(b) The Bureau will consider the application and inspect the drawings and parts to determine whether it will be necessary to make any tests.

(c) If no tests are necessary the applicant will be advised of the approval or disapproval of the change through the Director's office. (d) If tests are judged to be necessary the applicant will be advised of the material that will be required and of the necessary deposit to cover fee for test.*†

13.20 Material required for Bureau of Mines record. In order that the Bureau may know exactly what it has tested and approved, detailed records are kept of each investigation. These include drawings and actual equipment as follows:

(a) Drawings. The original drawings and specifications submitted with the application for the tests and the final drawings and specifications that the manufacturer must submit to the Bureau before the approval is granted to show the details of the gas mask as

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**For statutory and source citations, see note to § 13.0.

approved will be retained by the Bureau. The drawings are used to identify the gas-mask parts in the approval and as a means of checking the future commercial product of the manufacturer.

(b) Equipment. If the Bureau so desires, parts of the gas mask or a complete mask used in the tests may be retained as a permanent record of the investigation and of the gas mask submitted. Other apparatus will be returned to the manufacturer.

If the gas mask is approved the Bureau will require the manufacturer, as soon as his first permissible gas masks are available, to submit gratis one complete gas mask, with approval labels attached, as a record of his commercial product.

(c) Revision of requirements. In the original preparation and the subsequent revisions of these requirements there has been a continued endeavor to provide for safe, durable, and practical devices which will meet not only the demands of the existing situations for which canister gas masks are designed, but also the demands of potential and anticipated situations. However, with the continued adaptation of these devices to new situations and conditions it is possible that instances might arise where the protection afforded would be inadequate. The Bureau of Mines, with the cooperation of the manufacturers of gas masks and the users of gas masks, endeavors to be alert to these new situations. When any situation arises in which inadequacy of protection or unusual hazard attending the use of an approved device is established, the manufacturer or manufacturers of any devices involved are requested to affix caution statements or, if necessary, to cease marketing the device for the particular situation or condition until such changes or provisions as will provide adequate protection are made, it being understood that any provisions or changes made must be submitted to the Bureau of Mines and have this Bureau's approval before they are adopted. Should the situation require a change in the basic requirements and/or tests provided in this part, such changes will be issued as a supplement to the current schedule (this part) and later incorporated in a re

vision.*+

Sec.

PART 14-FILTER-TYPE DUST, FUME, AND MIST

RESPIRATORS

Sec.

14.0 Compliance with the require 14.9 Date for conducting tests.
ments necessary for obtaining 14.10 Witnesses.
approval.

14.1 Preliminary statement.

14.11 Notification to manufacturer of approval or disapproval.

14.2 Definition of a permissible dust, 14.12 Requirements for Bureau of

fume, and/or mist respirator.

14.3 Classes of filters.

14.4 Conditions under which respira-
tors will be tested.

14.5 Table of fees for approval.
14.6 Drawings and specifications re-
quired.

14.7 Requirement concerning control
of filtering characteristics.

14.8 Material required for investigation.

Mines approval.

14.14 How approvals are granted.
14.13 Changing details of tests.
14.15 Purpose of approval label.
14.16 Withdrawal of approval.
14.17 Changes in design subsequent to
approval.

14.18 Material required for Bureau of
Mines record.

14.19 Revision of requirements.

**For statutory and source citations, see note to § 13.0.

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