Experimental version of the gas mask. The first gas masks mostly used circular lenses made either of glass, mica or cellulose acetate. With the exception of the latter, these materials were quite brittle and needed frequent replacement. Later on, the Triplex lens style (two layers of glass and one layer of cellulose acetate in between) became more popular, and alongside the simpler cellulose acetate they became the standard into the 1930s. Panoramic lenses were not popular until the 1930s, but there are some examples of those being used even during the war (Austro-Hungarian 15M). Later, polycarbonate started being used for its strength.
In August 1916, a new gas mask version inspired by the German WW1 gas mask units was engineered, and produced in January 1917. Though, its usage only started in January 1918. This new mask called ARS mask (special respiratory device) or MCG (chemical warfare mask) was at that time the best protective unit against gases the Allied soldiers had to face. Breathing is made safe through air purifying cartridges for an efficient protection. The ARS well covered the face thanks to adjustable elastic straps and offers a good protection to eyes and breathing system. As it evolved, this mask used several filter types including filtering cartridges filled with agglomerated coal and glycerin water.
This mask was of fragile construction, required excess training to use effectively and largely immobilized men during a gas attack as they were concerned about their mask coming loose.
The German army used poison gas for the first time against Allied troops at the Second Battle of Ypres, Belgium on April 22, 1915. As an immediate response, cotton wool wrapped in muslin was issued to the troops by 1 May and followed by the Black Veil Respirator, a cotton pad soaked in an absorbent solution which was secured over the mouth using black cotton veiling. Seeking to improve on the Black Veil respirator, Macpherson created a mask made of chemical absorbing fabric and which fitted over the entire head. A 19.9” × 18.9” canvas hood treated with chlorine-absorbing chemicals, and fitted with a transparent mica eyepiece. Macpherson presented his idea to the War Office Anti-Gas Department on May 10, 1915, with prototypes being developed soon after. The design was adopted by the British Army and introduced as the British Smoke Hood in June 1915; Macpherson was appointed to the War Office Committee for Protection against Poisonous Gases. More elaborate sorbent compounds were added later to further iterations of his helmet (PH helmet), to defeat other respiratory poison gases used such as phosgene, diphosgene and chloropicrin.