A METHOD AND AN APPARATUS FOR PRODUCING A GASEOUS MEDIUM

The invention relates to a method and a system for producing a gaseous medium containing a sterilisation agent and for monitoring and regulating the concentration and quality of the gaseous medium. The method preferably includes concentration determination of a substance or agent in a sample of the gaseous medium in the presence of disruptive matter by means of light absorption, as well as an apparatus therefor. By measuring the light absorbency at two different wavelengths, it is possible to detect and compensate for the effect of disruptive matter such as dust particles, dirt and bubbles (aerosols). By also measuring the intensity of light emitted from the light source which has not yet passed through the measurement sample, simultaneously with the measurements of the absorbency of light allowed through the sample, at each measured wavelength, the actual concentration can be determined with improved accuracy. The method and the system are applied for the sterilisation of packaging materials, packaging containers and packing or filling machines within the food packing industry.