MCL and SCL series sirens are used in potentially explosive areas such a chemical/petrochemical plants and refineries where flammable dusts or fibres may be present in the atmosphere. Due to their power, these units are deployed in areas where there is a lot of background noise. These Ex de electromechanical sirens are suited for giving short warnings and not continuous operation. They emit a regular sound and very quickly reach optimal frequency. The regular sound emitted consists of a continuous pitch that the ear gets used to after a few minutes. The sound can be modulated or set to intermittent operation using a modulator to improve audibility.