Chemical permeation of breathing hoses used with supplied air respirators has largely been neglected. This study investigates the long-term permeation of methylethyl ketone (MEK), Turco paint stripper, aviation fuel and diesel through the wall of Arbin Rinba brand breathing hose. The testing used a new, simple test method that involves filling a short length of breathing hose with the chemical. While the MEK and components of the MEK permeated in a few hours, it took several weeks for significant permeation of the aviation fuel and diesel. The main implication of this work is that hoses need to be kept clean, as chemicals like MEK and Turco that permeate easily can contaminate the breathing air, while chemicals that permeate more slowly, like aviation fuel and diesel, show a potential for significant permeation if the breathing hose is stored contaminated. These findings affect the selection, service life and maintenance of breathing hoses