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Although the PHG/PH Hood had made important strides in protecting infantry from chemical weapons, the overall hood design had arguably exhausted its longevity. The PH hood masks hosted a fair number of notable flaws; it was not entirely effective against highly concentrated gases, it failed to filter phosgene effectively, the British Gas Department Laboratory noted that the PH hoods were near useless against arsine, and finally, the various chemicals soaked into the hoods would often leach out and burn soldiers skin when it was raining. By early 1915 it had become apparent that a 'box' type filter was required.
Bertram Lambert (1881 - 1963), a noted chemist and lecturer at Oxford University was one of the first to suggest a filtering solution housed within a 'box'. Initially, the British had received information from the Russians that activated charcoal was effective at filtering out the more troublesome gases such as Phosgene. Using large amounts of activated charcoal presented a problem; the industry in Britain at this time would not be able to make and maintain such a large supply quota. Thus Lambert laboured to create a box filter medium that, while still using charcoal, could be constructed of various other chemicals to increase filtration efficiency. In July 1915, Lambert submitted his box filter design to the Royal Army Medical College in London.
Lamberts original box filter was made from an army canteen. About 3/5ths of the box filter was standard charcoal. The other 2/5ths were made from a variety of chemicals - potassium permanganate, soda lime, crushed pumice (a porous volcanic rock) which was soaked in a solution of sodium sulphate. The charcoal used in these box filters were sourced from coconut shells (the practice of using coconut shells lasted well into WW2).
The box filter was a vast improvement over the conventional PH hood method of soaking the fabric in various compounds. Lamberts filter worked because of its employment of different chemical layers to deal with different chemical threats - organic gases (such as phosgene) were destroyed via oxidation from the permanganate and soda-lime granules absorbed acid gases (such as chlorine).
Edward Frank Harrison (1869 - 1918) and John Sadd developed the actual LBR apparatus itself. The LBRs facepiece was constructed of many layers of muslin cloth that were soaked in a solution of zinc-hexamine. Sadd developed the LBR mouthpiece. The LBR used a rubber hose that was strengthened via corrugation which stopped the rubber hose collapsing. The LBR mask itself was attached to the user via elastic straps which went around the back of the users head.
It should be noted that the LBR itself did not offer any eye-protection. This role was filled by pairing the LBR with sponge goggles. The rationale behind this was that exhaled breath often fogged the lenses on the PH hoods, so by keeping the eyepieces separate from the oral area, the problem of fogging was removed.
The LBR was first issued on the 16th February 1916. Men in static positions, such as machine gunners and artillery crews, were given overall priority for LBR issue. Once issued, the LBR did not come without its own issue - its weight. Due to the LBR filters weight and bulk, the LBR was difficult to use in narrow trenches. The overall bulk of the LBR led to several nicknames, the most used being Harrison Tower and Tar box. later in 1916 the motor corps and tank corps were issued large amounts of large box respirators and continued to use them well into 1917 when they were fazed out in favour of the SBR.
As soon as the LBR had gone into production, Harrison, Sadd and Lambert began improving the LBR and eventually constructed what would become the Small Box Respirator. No record of the total amount of masks produced by wars' end survives though it is estimated around 20-35 thousand masks were produced in all.
There were three main stages in LBR development, the Mk.I (used in the main image of this article), the Mk.II (shown in the colourised image below) and the experimental Mk.III. the differences between the MK.I and MK.II was the angletube, MK.IIs had welded angletubes whereas the Mk.I was bent copper or tin tubing. There was a transitional model although this is rarely seen. Finally the Mk.III utilised a facepiece with built in goggles, this is the rarest example and about 20 examples were produced for testing.