What wartime device did Franklin's coal research help improve?

Franklin’s coal research helped improve gas masks. Her wartime work examined how coal’s microscopic pores absorbed and released gases, knowledge that mattered for activated-carbon filters.

She worked at the British Coal Utilisation Research Association from 1942, studying coal’s density, porosity and fine structure. By comparing how gases and liquids moved through different coals, she established that pore size and accessibility varied with the way coal had been formed and heated.

That mattered because the carbon used in gas-mask filters had to trap harmful substances while allowing air to pass. Franklin’s findings helped scientists understand how coal-derived carbon could adsorb gases and how processing affected its performance. The research was also valuable for predicting coal’s usefulness as fuel.

The other options belong to different wartime technologies. Franklin did not conduct this coal research to improve radios, parachutes or radar sets. Her wartime contribution was materials science, linking the microscopic structure of carbon to protective equipment used during the war.