Abstract: The present invention is an improved method and apparatus for monitoring the status of particle filtration devices found in various filter units. The invention employs one or more light sources aimed across the filter units and one or more corresponding detectors that detect changes in light intensity from the light source. When a leak occurs whereby dust is released into the atmosphere around any given filter, the detectors will note a decrease in light intensity and will signal a problem. By using multiple light sources and detectors, or by getting signals from different angles from a single light source and detector, the present invention allows for quick and accurate pin-pointing of leakage problems.