Absorbents.
| Absorbent. | Composition. | Weight. | Volume. | |
|---|---|---|---|---|
| 1917. | No. 1. | Chemical Absorbent. | 66 gr. | 105 cc. |
| No. 2. | Impregnated Charcoal. | 36 gr. | 85 cc. | |
| No. 3. | Chemical Absorbent. | 15 gr. | 45 cc. | |
| 1918. | No. 1. | Impregnated Charcoal. | 58 gr. | 185 cc. |
| No. 2. | Chemical Absorbent. | 29 gr. | 45 cc. | |
| Total Volume of Absorbents, | 1917, 235 cc. = | 14.3 cu. in. |
| 1918, 230 cc. = | 14.0 cu. in. | |
| Total Weight of Absorbents, | 1917, 117 gr. | |
| 1918, 87 gr. | ||
| Volume of Air Space above Absorbents = 50 cc. = 3.1 cu. in. | ||
Body. The body of the canister is made of sheet metal (probably iron), which is protected on the outside with a coat of dark gray paint and on the inside with a japan varnish. For ease in assembling the sides of the canister have a gentle taper, and are formed so as to supply a seat for each of the follower rings. The protrusion or neck has about six threads to the inch, the pitch of the screw being 4 mm. The lower part of the body is rolled so as to give a finished edge, and the upper part of the cylinder is grooved to receive the top support.
The first screen is double, consisting of a coarse top screen five to six mesh, per linear inch, and immediately below, a finer screen of 30-40 mesh, per linear inch. The top support is a rigid ring of metal with two cross arms, which give added, strength to the ring and support to the screens. It springs into a groove at the top of the body and forms the support for the contents of the canister. Both screens are made of iron wire and the top support is made of iron (probably lightly tinned).
The second screen, which separates the second and third absorbents, is double, consisting of two disks of 30-40 mesh iron screen. Both screens are held in place by a follower ring.
The third screen is single, but otherwise it is exactly similar to the second screen. It serves to keep separate the layers of absorbents No. 1 and No. 2.
The fourth screen (30-40 mesh) is made of iron wire and is held to the bottom support by six cleats which are punched from the body of the support. The bottom support is simply a flanged iron cover for the bottom of the canister. It is punched with 79 circular holes each 4 mm. in diameter and is painted on the outside to match the body of the canister. The screen and the inside of the bottom support or cover are coated with a red paint.
American Mask
At the entrance of the United States into the war, three types of masks were available: the PH helmet, the British S. B. R. and the French M-2 masks. Experiments were made on all three of these types, and it was soon found that the S. B. R. offered the greatest possibilities, both as regards immediate protection and future development. During the eighteen months which were devoted to improvement of the American mask, the facepiece underwent a gradual evolution and the canister passed through types A to L, with many special modifications for experimental purposes. The latest development consisted in an adaptation of the fighting mask to industrial purposes. For this reason a rather detailed description of the construction of the facepiece and of the canister of the respirator in use at the close of the war (R. F. K. type) may not be out of place. The mask now adopted as standard for the U. S. Army and Navy is known as the Model 1919 American mask, with 1920 model carrier, and will be described on [page 225].