The 9920 half-mask airline respirator from Allegro offers a comfortable silicone facepiece. Low pressure continuous airflow gives continuous protection from airborne chemicals. Intended to be used with air supply provided by an ambient air pump. Popular with spray foam installers and welding applications. Low profile design fits under many welding helmets. Durable silicone rubber is hypoallergenic, resistant to many chemicals, and remains soft even after years of use. Standard double elastic suspension straps keep the mask comfortably in place. A 90 degree elbow allows the hose to be directed over the shoulder and out of the way. The hose itself is made of a lightweight corrugated material for flexibility and greater comfort. The hose may be switched to either side of the mask - however it works best for you. An OBAC quick-connect plug has a wide diameter opening and minimal air restriction. Great when you are using a low power ambient air pump. Nylon waist belt is included. NIOSH Approval No. TC-19C-355 Per NIOSH regulations, only the manufacturers (Allegro) approved airline hose may be used up to the 'point of attachment'.