Yellow Cross: Measures to protect against Mustard Gas

As a follow-up to my post on the introduction of mustard gas I have provided some details of the means that could be taken to protect against the weapon.

During the first three weeks after its first use on 12-13 July 1917, around 14,000 British soldiers were admitted to Casualty Clearing Stations affected by mustard gas. Of this number, 7,797 were Fifth Army casualties from the Ypres Salient.  This was more casualties than had been suffered by the British from gas shelling during the entire previous year.  Owing to the length of time required for recovery, more than three quarters had to be evacuated to hospitals on the lines of communication.

Mustard Victim 1

A British victim of the first mustard gas attack, recorded five days after exposure, this man was suffering from slight laryngitis and bronchitis but his eyes and skin were affected, the latter in areas of perspiration. W. G. MacPherson (ed.), History of the Great War Medical Services Diseases of the War, Vol. II, plate VI.

The British found unexploded shells marked with a yellow cross the morning after the first bombardment and within three days scientists, at the British Expeditionary Force’s (BEF) Central Laboratory at Helfaut, identified the contents as mustard gas.  Rapid treatment and secrecy prevented mustard from having a fatal effect on British morale.  Limited detection was possible from the smell of garlic or mustard and, until the Germans modified the shells, the distinctive ‘plop’ sound of their bursting.  Mustard gas evaporated in sunlight and, after a night bombardment, might not be noticed until sunrise when the vapour became dangerous.  In winter it could lie dormant for several weeks.  Those affected might not know they were contaminated for several hours, feeling no pain until conjunctivitis and skins lesions appeared, the sweaty parts being affected worse.

Mustard Victim 2

A British mustard gas victim recorded eleven days after exposure showing the effects of sitting on contaminated ground. This man’s injuries healed in three weeks. W. G. MacPherson (ed.), History of the Great War Medical Services Diseases of the War, Vol. II, plate VII.

Powdered chloride of lime became the standard means of removing mustard gas and was scattered over the shell craters and areas where the shells had burst.  The chloride of lime then had to be covered with clean earth both to camouflage it and because the smell prevented the detection of further mustard.  It was used in solution to wash guns, trees, etc which had been splashed.  Clean uniforms had to be issued immediately.

The French had already attached a pharmacist to each unit for anti-gas duties and in response to mustard created battalion and battery decontamination squads.  However, the affected areas were often so extensive that there was insufficient chloride of lime: the teams therefore had to choose the key points to treat, and prohibit access to others.  In late August fatigue uniforms impregnated with oil were issued while special overalls treated with boiled linseed oil and dyed horizon blue, impregnated gauntlets, and trench boots were developed.  The British were unimpressed by the French anti-mustard gas clothing, finding that neither the gloves nor the boots would keep out mustard.  They devised hooded overalls of black oiled cloth but the BEF Army Chemical Advisers did not consider that the amount of injury suffered from mustard gas warranted special clothing and concentrated instead on training and discipline.  Skin blistering could sometimes be prevented by directly applying chloride of lime and Britain, Germany and France all developed anti-mustard gas ointments, the French version Pommade Z comprising 10% chloride of lime in Vaseline.

Member of a French mustard gas decontamination squad, with oil impregnated overalls, ARS respirator and Vermorel sprayer containing chlorine of lime. © Simon Jones

German mustard shelling became intense with the series of offensives beginning in March 1918, and during the period of withdrawal of September – October when the British suffered 3-4,000 casualties per week.  Special clothing was again issued by the British from March but it was seldom possible to have it available when needed.  The USA ultimately developed the most extensive measures for both protection and decontamination in the form of mobile shower units.  Germany lacked the resources to produce either adequate protective clothing or replacement uniforms.  As the Allies began to use mustard, this presented Germany with a potentially disastrous situation.


Memorandum by the Chemical Advisor to the Canadian Corps, 27 September 1917, expressing concern that men were deliberately contaminating themselves with mustard gas. (Library and Archives Canada

Chemical weapons added novel ways to the already horrific means of injury and death during the First World War.  Morale, discipline and training were major factors in combating mustard gas.  The non-permanent nature of mustard injury led the Chemical Advisor to the Canadian Corps to report at the end of September 1917 that he believed men were deliberately exposing their eyes to mustard in order to gain a few weeks rest in hospital.  Tens of thousands of Allied soldiers were hospitalised for months with mustard gas.  Yet mustard gas presents a paradox because the mortality rate was far lower than for any other weapon and, by being kept away from the fighting at a time when casualty rates were extremely high, mustard gas will actually have saved the lives of many of its victims.


British troops temporarily blinded by mustard gas at an Advanced Dressing Station at Béthune, 10 April 1918. The Germans bombarded areas north and south of the Lys attack area on 7 – 9 April to cut off support from the flanks. Note the soldiers in the background staring at the casualties (Wikimedia Commons/ Imperial War Museum).

Further reading

Simon Jones, World War I Gas Warfare Tactics and Equipment, (Osprey, London 2007).

W. G. MacPherson (ed.), History of the Great War Medical Services Diseases of the War, Vol.  II, (HMSO, London, 1923).

Join me on a battlefield tour with The Cultural Experience:

Simon Jones Battlefield Tour Somme Poets 2019

The War Poets: Words, Music and Landscapes, 6th-9th July 2023

First & Last Shots 1914 & 1918

Medics & Padres in the Great War

Walking Ypres 1914-1918

Walking the Somme, Summer 2023

More Information about Battlefield Tours

German Yellow Cross mustard gas shell for 105mm howitzer.

Yellow Cross: The advent of Mustard Gas in 1917

Sawyer Spence (1)

Understanding Chemical Warfare in the First World War

Simon Jones, World War I Gas Warfare Tactics and Equipment

Contact me



One thought on “Yellow Cross: Measures to protect against Mustard Gas

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s