copper disk and fiber gasket and filled with a metal (such as Rose's metal) having a fusing temperature of approximately 94° C. Such fusible metal shall not be forced from the perforated safety cap by a pressure less than 2,250 pounds per square inch.
(k) (1) The closing valve of the highpressure gas container shall be provided with a 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 to 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 without use of wrenches or external levers.
(2) Main and bypass valves that control the flow of compressed oxygen or compressed air from the source of supply shall be so located that they can be manipulated readily by the wearer when the apparatus is being worn.
(1) When an apparatus is equipped with a gage for recording time or pressure of compressed-oxygen or compressed-air supply, the Bureau of Mines will test such a gage for accuracy of calibration. A variation of 3 atmospheres (approximately 45 pounds per square inch) will be allowed in comparison with the pressure shown by the Bureau of Mines standard pressure gage.
(m) (1) Apparatus having a separate pressure-gage connection shall be equipped with a valve to shut off the compressed-oxygen or compressed-air supply from the gage. The gage-connection valve shall be so placed that it can be manipulated readily by the wearer without interfering with the flow of compressed oxygen or compressed air from the high-pressure gas container to the circulatory system of the apparatus.
(2) An oxygen-generating, self-contained breathing apparatus shall be equipped with a timing device that will indicate accurately the number of minutes a person may continue to wear the apparatus with safety.
(n) Any pressure gage or timing device shall be so located that it can be read easily by the wearer.
(0) Apparatus equipped with a reducing valve giving a constant or automatic flow of oxygen or air shall be provided with a bypass valve that will permit compressed oxygen or compressed air to flow freely from the high-pressure gas container to the circulatory system of the apparatus, independent of the reducing valve.
(p) When the compressed-oxygen or compressed-air supply of the apparatus is controlled by automatic devices, such devices shall adjust themselves readily to the needs of the wearer.
(q) Apparatus in which the expired atmosphere is recirculated and which is equipped with either a mouth-breathing device or a facepiece shall be provided with an adequate saliva or moisture trap and release valve at the exhalation side of the inhalation and exhalation valve assembly and shall be so designed that, while the saliva or moisture trap and release valve are functioning, any atmosphere that may be external thereto cannot be drawn into the apparatus.
(r) Apparatus equipped with a mouth-breathing device 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.
(s) Self-contained breathing apparatus submitted for testing and approval shall not weigh more than 40 pounds when completely assembled and fully charged.
(t) Apparatus equipped with a facepiece shall meet the following requirements:
(1) The facepiece shall be so constructed as to assure quick, gastight fit on persons of widely varying facial dimensions and contours.
(2) The eyepiece(s) of the facepiece shall be of the nonshatter type and be so designed as to provide a satisfactory field of vision for persons of widely varying facial dimensions and contours. Air or oxygen shall enter the facepiece in such manner as will prevent excessive accumulation of moisture on the eyepiece(s). If fog -preventing solutions or other substances are applied to or furnished for application to the lenses of the eyepiece(s), such solutions or substances shall be nonirritating, odorless, and nonflammable.
(3) A facepiece shall be provided with elastic headbands that are adjustable and replaceable.
(4) If a facepiece is equipped with an exhalation valve, the valve shall be guarded to prevent distortion and injury.
(5) For self-contained breathing apparatus, approved before the effective
