The SR 500 is a battery-powered fan that, together with a filter and an approved head top, is included in the Sundstrm fan-assisted respiratory protective device systems. The SR 500 can be used as an alternative to filter respirators in all situations in which these are recommended. This applies particularly to work that is hard, warm or of long duration. The human interface may consist of a hood, face shield, half mask or full face mask. The fan is equipped with a filter, and the filtered air is fed through a hose to the human interface. The pressure then generated prevents surrounding pollutants from penetrating into the mask. The characteristics of the SR 500 are as follows: The battery is of lithium-ion type Two battery alternatives, i.e. STD (Standard 2.2 Ah) and HD (Heavy Duty 3.6 Ah) The charging time for the Standard battery is around 1.5 hours and for the Heavy Duty battery, about 2 hours Equipped with two filters/combined filters Operating time of up to 13 hours The same