He was the husband of Jessie Blanche Fulford.
Aaron enlisted in the Army on April 3, 1918 at age 22 and after basic training was assigned to the Chemical Warfare Service. This was a branch of the military that was created in July 1918.
The CWS had a defense unit and an offensive detachment. Aaron served in the defense unit. They designed, created and tested gas masks and protective clothing for the US troops.They used the actual chemicals to do the testing.
When the US entered WWI it had no gas masks. The first troops went to Europe without any protection from the mustard gas and other chemicals being used by the Germans and British troops.
The US started making gas masks based on the British model but later developed their own. The Chemical Warfare Service was also supposed to train US troops on how to protect themselves from the gas.
The spring of 1918 saw the highest use of chemicals in the war and US troops had very high casualty rates.
Aaron Bell was in the Chemical Warfare Service until February 1919, three months after the end of the war. He was fortunate the war ended before he was sent overseas so he never had to wear the mask in combat.