Optrel® Helix Pure Air 2.5The Helix Pure Air 2. 5 the new PAPR and slide up welding & grinding helmet with a panoramic field of vision and a brightness level of 2. 5 built for welding in the toughest conditions. With the Helix 2. 5, youre prepared for all welding tasks that require a large field of vision and frequent switching between transparent and protective filters. With a light level of 2. 5 for welding and a shade range from 5 to 12, its the ideal choice for a wide