Standard on all MSA Air Masks Wide variety to meet all types of budgets, use requirements and weight preferences High-quality design and proven technology Designed for quick activation, even with gloved hands . Type C Supplied-Air Respirators, commonly called air-line respirators, provide long-duration respiratory protection. Systems generally consist of a full- or half-mask facepiece connected by air-supply hose to an air source. When connected, respirators deliver respirable air to users. This guide is designed to aid in understanding specific pressure-demand and constant flow air-line systems from air source to respirator. Complete air-line kits consisting of frequently-ordered systems for ease of ordering are listed as well.