Apparatus for monitoring the effectiveness of a gas mask comprises comparing a range of pollution readings rather than relying on a calibrated sensor

摘要

The quality of the absorbent in a gas mask filter is measured at points (8,9,10), placed at equal intervals in the absorbent bed (3) along the flow path 6 - 7, and compared with that at a reference point (12) at the entry to the filter. Gas is drawn sequentially from the sample points by pump (13) through a Photo-Ionization-Detector (14) whose readings are collected at (15) and presented as dimensionless quotients of the reference reading in the form of a bar chart. A limiting value of 1, usually first shown at point (8), indicates exhaustion of the absorbent and hence the need for its replacement.