Indian infantry in the trenches, prepared against a gas attack (Photo 24-300)

The Hypo helmet, or British Smoke Hood (its official name), was an early British

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

gas mask, designed by

Cluny MacPherson Ewen MacPherson of Cluny, also known as "Cluny Macpherson" (11 February 1706 – 30 January 1764), was the Chief of Clan MacPherson during the Jacobite Rising of 1745. He took part as a leading supporter of Prince Charles Edward Stuart. After th ...

Earlier designs

The German army used

poison gas Many gases have toxic properties, which are often assessed using the LC50 (median lethal dose) measure. In the United States, many of these gases have been assigned an NFPA 704 health rating of 4 (may be fatal) or 3 (may cause serious or perman ...

for the first time against Entente troops at the

Second Battle of Ypres During the First World War, the Second Battle of Ypres was fought from for control of the tactically important high ground to the east and south of the Flemish town of Ypres in western Belgium. The First Battle of Ypres had been fought the pr ...

, Belgium on 22 April 1915. As an immediate response, the British began issuing cotton wool wrapped in muslin to its troops by 3 May. This was followed by the Black Veil Respirator, invented by John Scott Haldane, which began to be issued to troops on 20 May 1915. The Black Veil was a cotton pad soaked in an absorbent solution which was secured over the mouth using black cotton veiling. The veiling could be drawn up to cover the eyes, providing some protection against

lachrymatory agent Tear gas, also known as a lachrymator agent or lachrymator (), sometimes colloquially known as "mace" after the early commercial aerosol, is a chemical weapon that stimulates the nerves of the lacrimal gland in the eye to produce tears. In ad ...

s, however the mask itself still only provided little protection against chlorine gas. It was also of fragile construction, required training to use effectively and largely immobilized men during a gas attack as they were concerned about their mask coming loose.

Development and design

Seeking to improve on the Black Veil Respirator, Dr Cluny Macpherson created a mask made of chemical absorbing fabric and which fitted over the entire head. MacPherson had seen a German soldier putting a bag over his head after a gas attack and sought to replicate the design. Macpherson presented his idea to the

War Office The War Office was a department of the British Government responsible for the administration of the British Army between 1857 and 1964, when its functions were transferred to the new Ministry of Defence (MoD). This article contains text from ...

Anti-Gas Department on 10 May 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 and manufactured until September 1915. 2.5 million mask were manufactured before being superseded by subsequent designs. The design consisted of a canvas hood treated with chlorine-absorbing chemicals, and fitted with a single rectangular mica eyepiece. It was simply a

khaki The color khaki (, ) is a light shade of tan with a slight yellowish tinge. Khaki has been used by many armies around the world for uniforms and equipment, particularly in arid or desert regions, where it provides camouflage relative to sandy ...

-coloured

flannel Flannel is a soft woven fabric, of various fineness. Flannel was originally made from carded wool or worsted yarn, but is now often made from either wool, cotton, or synthetic fiber. Flannel is commonly used to make tartan clothing, blankets, ...

bag soaked in a solution of

glycerin Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...

and

sodium thiosulphate Sodium thiosulfate (sodium thiosulphate) is an inorganic compound with the formula . Typically it is available as the white or colorless pentahydrate, . The solid is an efflorescent (loses water readily) crystalline substance that dissolves well ...

. The soldier placed it over his head and tucked the bottom into his tunic. No inlet or exhaust valve was provided, and the wearer's lungs forced the air through the material making up the bag.

Later versions

This primitive type of mask went through several stages of development before being superseded in 1916 by the canister gas mask. More elaborate

sorbent A sorbent is a material used to absorb or adsorb liquids or gases. Examples include: *A material similar to molecular sieve material, which acts by adsorption (attracting molecules to its surface). It has a large internal surface area and good th ...

compounds were added later to further iterations of the helmet (

P Helmet The P helmet, PH helmet and PHG helmet were early types of gas mask issued by the British Army in the First World War, to protect troops against chlorine, phosgene and tear gases. Rather than having a separate filter for removing the toxic ch ...

and

PH helmet The P helmet, PH helmet and PHG helmet were early types of gas mask issued by the British Army in the First World War, to protect troops against chlorine, phosgene and tear gases. Rather than having a separate filter for removing the toxic ch ...

), to defeat other respiratory poison gases used such as phosgene,

diphosgene Diphosgene is an organic chemical compound with the formula ClCO2CCl3. This colorless liquid is a valuable reagent in the synthesis of organic compounds. Diphosgene is related to phosgene and has comparable toxicity, but is more conveniently handl ...

and

chloropicrin Chloropicrin, also known as PS and nitrochloroform, is a chemical compound currently used as a broad-spectrum antimicrobial, fungicide, herbicide, insecticide, and nematicide. It was used as a poison gas in World War I. Its chemical structural f ...

References

Bibliography

* * * * World War I military equipment of the United Kingdom Gas masks of the United Kingdom {{UK-mil-stub