Hertha and William Ayrton acted as guardians for artist and suffragette Ernestine Mills after the death of Mills' mother Emily "Mynie" Ernest Bell in 1893. (Her father, writer Thomas Evans Bell, had died in 1887.) They stayed close and in May 1915, Hertha Ayrton tested an 'anti-gas fan’ in Mills' back garden in Kensington. It was later adopted as a device to clear poisonous chemical gases from British frontline trenches during the First World War. The story was transmuted into a scene in the 1924 novel The Call written by Ayrton's step-daughter Edith Zangwill, daughter of William and his first wife, doctor Matilda Chaplin Ayrton).