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(e) Direct leakage and man-tests. To determine whether the submitted respirator has a certain minimum filtering efficiency and whether on man-test there is any leakage of unfiltered air, three complete respirators will be worn by three men having different facial features (full, more or less average, and lean) in a room containing a plainly visible atmospheric suspension of powdered bituminous coal. The men shall do moderate work (as at approximate rate of 3.5 miles per hour) and resting (seated) alternately 5 minutes of each for a total period of 30 minutes.

To meet the requirements of this test the forced nasal discharge at the end of the test period (as shown on a white cloth), the sputum, the nasal cavities as examined by aid of a speculum and illumination, and that part of the face covered by the face piece of the respirator must not show appreciably more black particulate matter than similar observations made before entering the coal-dust atmosphere. (f) Respirator filter element tests. Unless otherwise stated, a new respirator filter element shall be used for each of the tests listed in this section.

Type A: Dusts. Six respirators will be tested on a mechanical testing apparatus under the following conditions:

(1) High-dust-concentration test. Three respirators will be tested on a mechanical testing apparatus under the following conditions:

Humidity: 40-70 percent relative humidity.

Temperature: Room temperature (approximately 25° C.)

Rate of air flow: 32 liters per minute, continuous flow.

Test suspension-50±10 milligrams per cubic meter of ground flint, air-floated (99+ percent through 325 standard-mesh sieve), and which consists of 99+ percent free silica (SiO2).

The particle-size distribution of the test suspension shall not exceed a geometric mean of 0.6 micron and a standard geometric deviation of

1.90.

Length of sampling period-three 30-minute periods for each respirator.

Tested in this way, the total amount of the test suspension unretained must not exceed 9.0 milligrams for the three respirators or 4 milligrams for any one of the three respirators.

Respirators with filter elements, designed for cleaning and re-use, will be put through the above tests (using one respirator with the same filter element) on three different occasions. The manufacturer's directions for cleaning the filter element will be followed not more than once for each of the three occasions. Requirements, same as above. (2) Low-dust-concentration test. Three respirators will be tested on a mechanical testing apparatus under the following conditions: Humidity: 40-70 percent relative humidity.

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

Rate of air flow: 32 liters per minute, continuous flow.

Test suspension: 5±2 milligrams per cubic meter of the same test suspension (ground flint) as used in test (1) above.

Length of sampling period: Two 156-minute periods for each respirator. Tested in this way the total amount of the test suspension unretained must not exceed 30 milligrams for the three respirators or 12 miligrams for any one of the respirators.

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In the case of respirators to be marketed for use against poisonous dusts, such as lead, manganese, vanadium, cadmium, and organic dusts of known or questionable toxicity, special tests may be run to determine the efficacy of the respirator in question against the poisonous dust. Type B: Fumes. Six respirators will be tested on a mechanical testing apparatus under the following conditions:

(1) For low-plugging fumes (those which do not cause an appreciable increase in resistance to the flow of air through a filter) such as those of lead, manganese, copper, and chromium.

Three respirators will be tested on a mechanical testing apparatus under the following conditions:

Humidity: 40-70-percent relative humidity.

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

Rate of air flow: 32 liters per minute, continuous flow.

Test suspension: 15±5 milligrams per cubic meter of lead, as lead oxide fume produced by the decomposition and combustion of lead tetra-ethyl.

Length of sampling period: Two 156-minute periods for each respirator. Tested in this way, the total amount of the test suspension unretained by each respirator must not exceed 1.5 milligrams in any

case.

Test (2) below is also required for respirators on which approval for all fumes is desired.

(2) For fast-plugging fumes, such as those of magnesium, zinc, cadmium, aluminum, and antimony, the respirator must pass the requirements of test (1) for type B respirators and the following additional test.

Three respirators will be tested on a mechanical testing apparatus under the following conditions:

Humidity: 40-70-percent relative humidity.

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

Rate of air flow: 32 liters per minute, continuous flow.

Test suspension: 100±25 milligrams per cubic meter of freshly formed magnesium oxide produced by burning magnesium ribbon.

Length of sampling period: Until air which originally contained approximately 200 milligrams of magnesium oxide has been pulled through the respirator. When tested in this manner the respirator must meet the requirements for resistance to flow of air as required in paragraph (d).

Respirators with filter elements designed for cleaning and re-use, will be put through test against magnesium oxide on three different occasions using one respirator with the same filter element. The manufacturer's directions for cleaning the filter element will be followed before each test.

Type C: Mists. Nine respirators will be tested under the following conditions:

(1) Chromic acid mist. Three respirators will be tested on a mechanical testing apparatus under the following conditions:

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

Rate of air flow: 32 liters per minute, continuous flow.

Test suspension: 15±5 milligrams per cubic meter of chromic acid mist (calculated as chromic acid) produced by electrolyzing an (200-500 grams of chromic acid per liter) of chromic acid.

aqueous solution

Length of sampling period: Two 156-minute periods for each respirator. Tested in this way, the total amount of chromic acid unretained

by each respirator must not exceed 1 milligram in any case.

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The additional tests described under (2) and (3) of type C are also required for respirators on which approval against all mists is desired.

(2) Lead-paint mist. Three respirators will be tested on a mechanical testing apparatus under the following conditions:

Humidity: 40-70-percent relative humidity.

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

Rate of air flow: 32 liters per minute, continuous flow.

Test suspension: 300-600 milligrams of lead per cubic meter produced by spraying a paint, having the following composition: White lead (paste having approximately 91 percent white lead and 9 percent linseed oil by weight), 100 grams; linseed oil, 50 cubic centimeters; and steam-distilled turpentine, 25 cubic centimeters.

Length of sampling period: Two 156-minute periods for each respirator. Tested in this way the total amount of lead unretained by each respirator must not exceed 1.5 milligrams in any case.

(3) Water mist carrying silica dust. Three respirators will be tested on a mechanical testing apparatus under the following conditions:

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

Rate of air flow: 32 liters per minute, continuous flow.

Test suspension: 10±5 milligrams per cubic meter of silica dust produced by spraying a 2-percent aqueous suspension of ground flint, air-floated (99+ percent through 325 standard-mesh sieve), which consists of 99+ percent free silica (SiO2).

Length of sampling period: Two 156-minute periods for each respirator. Tested in this way the total amount of silica dust unretained by each respirator must not exceed 5 milligrams in any case.

Respirators designed for cleaning and reuse will be put through the test against the water mist carrying silica dust on three different occasions while using the same filter element. The manufacturer's directions for cleaning will be followed after each test. Requirements are the same as above.

(g) Tests covering special combinations for different types of atmospheric particulate matter. Respirators may be tested against any two of the three types (dusts, fumes, and mists) of atmospheric particulate matter or against two or more of the various test suspensions of the three types of particulate matter.

To meet the approval of the Bureau of Mines it will be necessary that the respirator meet all the separate requirements.

Type D: Tests for protection in air against all dusts, fumes, and mists. These respirators are for protection in air against all substances included in the preceding types, and in the same degree. The respirators will be tested as described under types A, B, and C. To meet the approval of the Bureau of Mines it will be necessary that the respirator meet all the separate requirements.

Special-type tests for protection in air against a single substance of the types A, B, or C of atmospheric particulate matter. Similar tests to those described will be performed on other special suspensions of atmospheric particulate matter of types A, B, and C and will be arranged as the need arises.**

14.13 Changing details of tests. If the mechanical or other features of a respirator render it advisable to omit any of the

**For statutory and source citations, see note to § 14.0.

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tests or part of a test previously described or to perform accessory tests the Bureau reserves the right to modify the test in such a manner as to obtain substantially the same information and degree of safety as is provided by the tests described.**

14.14 How approvals are granted—(a) Approval letter. After all inspections and tests have been satisfactorily completed and suitable drawings and specifications have been placed on file the manufacturer will be given official notification by letter from the Director of the Bureau of Mines, Washington, D. Č., that his respirator has been judged to have met the requirements of this schedule; he shall then be free to advertise such a respirator as permissible.

No verbal reports of the Bureau's decisions concerning the investigation will be given, and no informal approvals will be granted. (b) Approval label. With the approval letter the manufacturer will receive photographs of designs of approval labels for the respirator container and for filter-unit containers. These labels shall bear the seal of the Bureau of Mines and contain statements in effect, as follows:

Permissible

(respirator or filter)

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

Approved only when assembled with

This

(respirator or filter)

for

(Name of type of atmospheric particulate matter or particular substances)

(Approval number of filter or facepiece) is of the mechanical filter type and is approved

only for protection against the above-mentioned type of atmospheric particulate matter. It will not protect against harmful gases or vapors or an atmosphere having a deficiency of oxygen.

When deemed necessary other inscriptions, appropriate instruction, and caution statements will be included.

The manufacturer shall have this design legibly reproduced on each permissible respirator container and filter-unit container. Proofs of the size and position of the approval label shall be submitted to the Bureau of Mines for approval before adoption by the manufacturer.

To be able to identify approved respirators, the facepieces and filter units shall be marked by stamping, stenciling, or labeling in a legible and permanent manner with the approval number assigned to the device and the type of particulate matter or particular substance for which the device is approved, in letters and figures at least one-eighth inch high, placed in a position plainly visible. Examples of marking are "B. M. ---- Type B" or "B. M. ---- Lead fume."*+

14.15 Purpose of approval label. The approval label identifies the respirator so any one can tell at a glance that it is permissible. By means of the approval label the manufacturer can point out that his respirator complies with the specifications of the Bureau of Mines and that it has been judged to be safe for use under the conditions stated on the approved label. Permission to place the Bureau's approval label on his respirator obligates a manufacturer to maintain the quality of his product and to see that each respirator in all its

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**For statutory and source citations, see note to § 14.0.

parts is constructed according to the drawings or records that have been accepted by the Bureau for this respirator and that are in the Bureau's files. Respirators that exhibit changes in design or include any parts that have not been approved are not permissible respirators and must not bear the Bureau's approval label.*+

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

14.17 Changes in design subsequent to approval. All approvals are granted with the understanding that the manufacturer will make his respirator according to the drawings, designs, and specimens that he has submitted to the Bureau and that have been considered and included in the approval. When he desires to make any change in the design of a permissible respirator he should first 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 respirator parts affected to the Supervising Engineer, Bureau of Mines Experiment Station, 4800 Forbes St., Pittsburgh, Pa.

(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.*t

14.18 Material required for Bureau of Mines record. The Bureau will keep for record purposes 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 respirator as approved, will be retained by the Bureau. The drawings are used to identify the respirator parts in the approval and as a means of checking the future commercial product of the manufacturer.

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

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

14.19 Revision of requirements. In the preparation of the requirements in this part, an endeavor has been made to provide

*For statutory and source citations, see note to § 14.0.

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