a fan - supported gas mask and breathing equipment with a fan unit with adjustable delivery output such that the delivery output of the fan and detection sensor will be automatically adjusted to the necessary filter property , depending on the type of the filter insert used . to achieve this , the filter connection and the filter insert are provided with a marking , which characterizes the filter property , on the one hand , and , on the other hand , actuates electric contacts for setting the necessary fan output and , if desired , for actuating a detection sensor .