Speedglas™ Sound-Dampening Breathing Tube SG-50W is required when used with Adflo™ Powered Air Purifying Respirator with high-efficiency (HE) filter and organic vapor/acid gas cartridge and Speedglas™ Welding Helmet 9100-Ai, 9100MP and M-Series. Use of the tube is required at all times for the Versaflo™ Respiratory Helmet Assembly M-405 and M-407 and the Adflo™ Powered Air Purifying Respirator regardless of filter choice. Speedglas™ SG-50W is not NIOSH-approved with V-Series Supplied Air Valves.