The Breathing Air System removes excess moisture, solid particles, oil and oil vapor, and carbon monoxide that may be present in ordinary compressed air. The system meets health and safety requirements, and can feed face masks, hoods, and other breathing devices. With six stages of purification, the unit supplies OSHA Grade D breathing air for flows from 15 to 940 scfm. An activated carbon filter removes gases normally absorbable by activated carbon, and a moisture indicator features visual color change. The system includes air sample ports for analyzer installation, and options include a recommended Carbon Monoxide monitor.