The original Imperial War Museum exhibit caption provides the following information: '...was in daily use at the Front since May, 1916; principally for clearing-outs, shell-holes, mine craters, etc., of the foul gases that always accumulate in them under shell fire. These can now be cleared in from a few seconds to a few minutes, and can therefore be consolidated immediately after taking instead of having to be left for hours, and sometimes for days, before they can be entered. They are made of waterproof canvas stiffened with cane, with a wooden handle. The blade has a semi-rigid centre, with loose end and side flaps, and the back has an extra very limited hinge in it to enable it to accommodate itself to the varying shapes of the backs of parapets, corners of traverses etc. They are 3 feet 6 inches long, have a blade 15 inches square, weigh less than 1lb., can be folded and carried in the braces behind the pack.' The fan was the outcome of the experiment, begun soon after the first German cloud gas attack, to find - 'some obstacle which, when oscillated in the air close to our trenches, would set up currents which would, while sending the noxious gases back towards the enemy, at the same time keep our men well supplied with fresh air from behind.'
The Ayrton anti-gas fan was designed in the First World War to be used to attempt to drive back an enemy poison gas cloud and for clearing gas from trenches and dug-outs. It was invented by Hertha Ayrton, a pioneering physicist, electrical engineer, mathematician and inventor, in response to the first major use of poison gas by German forces in April 1915.
Ayrton, educated at Girton College, Cambridge, was the first woman to be elected to the Institution of Electrical Engineers in 1899. She was also the first woman to be awarded a prize from the Royal Society, being awarded the Hughes Medal in 1906 for her research on the motion of ripples in sand and water and her work on the electric arc.
Ayrton was a prodigious inventor who submitted her idea of an anti-gas fan to the 'Inventions Committee' of the British Army's General Headquarters in 1915. The Committee rejected the idea, but after appeals to prominent figures including David Lloyd George and Douglas Haig, a trial was arranged at Helfaut in France. While some accounts suggest the trial showed the fan to be ineffective, ultimately around 104,000 Ayrton anti-gas fans were supplied to the British Army in France. A further 50,000 were ordered by the US Army as they began to arrive on the Western Front in 1918.
A development model is also held in the collections, see MOD 1110, and in June 1917 Mrs Ayrton devised a mechanically driven fan, see MOD 1108.