Porous glass optical fiber sensor as an end-of-service indicator for respiratory cartridges

Sections of porous glass optical fibers were fabricated and characterized. They were found to show a significant drop in light transmittance when exposed to solvent vapors. A sensor has been developed that uses these porous fibers to detect the saturation of activated charcoal inside cartridges. The sensor is sensitive to toluene vapors at a few thousand ppm. Various approaches for increasing this sensitivity are proposed.