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Spectrophotometric method for contamination control of gas media filters

The possibility of measuring air filter contamination by colourimetry methods is investigated. It is found that the optical density Drel, measured relative to a clean filter surface can be used to assess filter contamination with coloured contaminant. This indicator is convenient for the specific weight of the contaminant in the range of 5-50 g/m2 for substances with a density ρ < 1 g/cm3, and for the specific weight of the contaminant 10-250 g/m2 for ρ > 1. It is shown that in case of a colour dust contaminated filter, the most reliable indicator is the colour difference ΔE of the contaminated surface relative to the clean one. The analysis of colour charts a*b*, a*L* and b*L* constructed in the CIE L*a*b*-1976 system shows that the lightness value ΔL* is appropriate to measure dark contaminants, and the value ΔE is acceptable for light contaminants.