🔍 Key Concepts

• Grade D breathing air requirements (what they are intended for) • Difference between air used to operate machinery vs. air used for people to breathe • Typical systems on board that require clean, breathable compressed air

💭 Think About

• Ask yourself: Which option clearly involves air that will be breathed by a person, not just used to move mechanical parts? • Which systems (from the choices) would be sensitive to contaminants like oil mist, CO, or moisture from the air supply? • Think about where air quality standards and exposure limits (like for workers) would be most critical among these choices.

✅ Before You Answer

• Verify which systems are related to life support or respiratory protection rather than hydraulic or mechanical power. • Check your notes on Grade D breathing air – does it appear under topics like SCBA/SCUBA, supplied-air respirators, or accumulator systems? • Confirm that the choice you’re leaning toward involves human inhalation of the air, not just using it as a power medium.