Chemical permeation testing of air-supply hoses.
Permeation of chemicals through the walls of air-supply hoses used with respirators is an underrecognized problem in industry. Transport of chemicals through the wall of a hose occurs in the same manner as through gloves and chemical suits--driven by the chemical concentration gradient--but for air-supply hoses, the chemical evaporating inside the air-supply hose is inhaled. A simple method based on the mathematical equivalence of filling a homogeneous hose with a chemical, to immersing it in a chemical, has been developed. The method requires a short section of hose to be filled, plugged, and weighed at intervals to determine the breakthrough detection time and the cumulative permeation per meter. The method has been tested experimentally, and calculations show that permeation of an air-line respirator hose could be a significant source of respiratory exposure, particularly for users of demand-type, supplied-air respirators.