WIP: Please be patient, documentation is being timelined to make for a better article.
- Baroque4Days
The Light Anti-Gas Respirator was the first British respirator described as a self-containred respirator, a type of respirator which did not require any other equipment apart from the facepiece and container, unlike the General Service Respirators before it. By the end of its life, 10 marks had been created and issued, along with a few modified variants.
Prior to the officially recognised Mk. I Light A. G. Respirator design, an experimental Mk. I design was proposed, created and later trialled to see how well the concept of a self-contained respirator, a type of respirator with the filter attached by means of a female threaded port on the side of the respirator, would perform in specialist combat situations. After some time, by the end of 1941, the design proved unusually successful, leading to the adoption of the Mk. I Light Anti-Gas Respirator by 1942, and later mass issue of the design after much improvement by during the latter years of the war.
Inception
On the 4th February 1941, the initial request for a special respirator to be designed for assault troops was put to the C.D.E.S. (Chemical Defence Experiment Station), Porton, Wiltshire but the then Inspector of Chemical Warfare of the War Office, Brigadier A. K. Crawford (possibly a misspelling of K. N. Crawford). The project was discussed at a meeting on the 15th of July, specifically to discuss the design of a special light respirator for assault troops and other special troops. At the meeting were many people, including some from the War Office and Ministry of Supply among many others from inside and outside of the CDES and, of course, Brigadier Crawford himself. The members from Porton are known to have been involved in and out of this project but, as with virtually all development of respirators since the First World War, it seemed that Major John Ambrose Sadd was somewhat in charge of the project.
Development & Discussion on the Design
The Experimental Mk. I design was created only from existing components from two of the many types of civilian-issue respirator, the Small Child Respirator (SCR), and the Civilian Duty Respirator (CDR). To create each of the Light Respirator components, i. e., the valve holder, rubber mask, container mount and container, various parts from these two respirators were either modified or assets from them were reused to shape new components. The following details roughly how each component was seemingly constructed based on visual inspection, this process was not documented.
Rubber Mask
The rubber mask was identical to that of the CDR with only a single modification applied to create the mask of the Light Respirator. Civilian Duty Respirators would typically have a blanked mic port which could but cut into to allow the connection of a No. 1 or No. 2 Respirator Mic. On the light-type mask, what would later be referred to as the No. L1 Rubber Mask, this area is transformed from a 31,75 mm (1 1/4 inch) diameter microphone port to a roughly 63,5 mm (2 1/2 inch) aperture. This aperture, much like the large opening at the front of the rubber mask, has a cylindrical shape and thus allows for the insertion of the container mount. The rubber overlap from the mask is then fastened down onto the container mount by means of wire and tape.
To create this aperture, it is unclear whether it was the mould that was modified or the mask itself. Regardless, based on observation alone, there does not appear to be any sort of patchwork to the rubber, heavily suggesting that the CDR mould was modified prior to a rubber mask being created.
It should also be noted that on the CDR masks, an aperture would be cut into the triangular base between the eyepieces and would also be fitted with support fabric, characteristic of the late-war Light-type Respirators. This, however, was not something that was carried over into the early production of Light-type Respirators and, of course, no such aperture was cut as there was no need to install a flutter-type outlet valve due to the creation of the Light-type valve holder.
Valve Holder
from GasMasksUK
The way in which the valve holder was created is unclear, but, origins can be traced back to the container designed for use with the Small Child Respirator. The component found inside many containers of the period which served as a divider, constructed from metal with holes to allow air to pass through, was known as a diaphragm. This valve holder was made from diaphragms and also part of the canister body, of the SCR container.
from GasMasksUK
Inside of this, a few newly made components could be found, namely the seating and the outlet valve. As only one example of this respirator has been discovered, it would be unrealistic to dissect the valve holder to inspect these components, though, from visual inspection, it does appear that the seating and outlet valve were either identical or, at least, very similar to the types used with the actual L1 valve holder, i.e. L1 Seating and L1 Outlet Valve.
It is unclear why, but these parts were not repainted and were tested in the iconic blue colour of the SCR container.
Container & Container Mount
.jpg){kind=link}
Experimental container design
The container and container mount pair were mostly based on the Small Child Respirator container mount and container, in that a 60mm thread was used to allow the two to be simply screwed into each other. The container mount used on the Experimental Light Respirator was identical to the type used on the SCR, only now it was painted black instead of blue. This container mount, officially known as Container Mount Mk. I, retained the inlet valve disk and, as was the case with the SCR, could be simply wired on to the newly cut aperture into the CDR-type rubber mask. Once attached, a new container design was required to be light enough to avoid excessive weight on one side of the mask.
A new container was eventually created and dubbed the Mk. I Light Container, or at least the experimental version of what would become the actual Mk. I Light Container. The initial model was painted black and, due to the heavy limitations put on the team developing this, and based on the shortage of resin-wool filter material, the container used an asbestos-wool filter to save costs during the trials.
This container was made up of two sub-containers, one housing the charcoal mix and with the 60mm thread at the top of its body, and the other housing the asbestos-wool filter mix with an inlet at the bottom. This sub-container also had a distinctive lip around the base. These two were then attached together using a white fabric-tape, just as the contex pre-filters were often attached to civilian respirators during this period.
from GasMasksUK
Facepiece Assembly
On the completion of the former three components, respirators would be assembled fairly similar to how they were to be assembled but with a few differences. Whilst the container mount was attached by means of wire and tape to the aperture cut into the side of the CDR rubber mask, the valve holder was secured in place with the CDR-style toggle clip, the set-size locking clamp which would often be used to secure the container to the CDR. Underneath this was a brown tape of length enough to allow the wearer to carry the mask in the alert position, even without the haversack.
Once the container mount and valve holder are attached, the experimental container could then be screwed well-home into the container mount, no different to how we might expect. This would now render a respirator complete and ready for trial. As mentioned in the previous section, only 1,000 of these were made for the trials discussed below, and many of these construction practices were abandoned, whilst some were adopted, during the production of the official Mk. I Light A. G. Respirator design in 1942.
Trials
Improvements & Comparison to the final L Mk. I Design
References
- Special Light Respirator for Assault Troops: Development - Held at the National Archives, Kew as WO 188/897 (scans by Baroque4Days)
- Report on service trials with experimental light type respirators - Held at the National Archives, Kew as WO 189/2249 (scans by Baroque4Days)
- Photos from the collection of GasMasksUK and an unknown former owner of the only known example.
- Patent No. 555,668, Improvements in Respirators, filed by J. D. Pratt of the Ministry of Supply and Major J. A. Sadd of the C.D.E.S., Porton. - https://worldwide.espacenet.com/patent/search?q=pn%3DGB555668A