RMGA Medical Gas Systems Design & Components 4 — Questions and Answers
Question 1: When sizing a medical gas pipeline, what factor primarily determines the pipe diameter selected for a given branch?
- The number of floors the pipe passes through
- The simultaneous use factor applied to the total connected outlet load (Correct answer)
- The distance from the bulk storage area to the zone valve
- The gas storage vessel pressure rating
Correct answer: The simultaneous use factor applied to the total connected outlet load
Pipe sizing is based on the simultaneous use (diversity) factor — not all outlets operate at once, so designers apply a usage factor to determine actual peak demand.
Question 2: A medical gas cylinder manifold system with automatic switchover is required to have how many independent supply banks?
- One primary bank only
- A primary bank and one reserve bank
- A primary, secondary, and reserve bank (Correct answer)
- Four independent banks for continuous redundancy
Correct answer: A primary, secondary, and reserve bank
NFPA 99 requires cylinder manifolds to have primary, secondary, and reserve supply banks to ensure uninterrupted gas supply during changeout.
Question 3: Which medical gas is stored as a cryogenic liquid in bulk storage systems due to its extremely low boiling point?
- Medical air
- Nitrous oxide
- Nitrogen (Correct answer)
- Carbon dioxide
Correct answer: Nitrogen
Nitrogen has a boiling point of -196°C (-321°F) and is stored as a cryogenic liquid in bulk systems, vaporizing to gas through ambient vaporizers before distribution.
Question 4: Under NFPA 99, what color is assigned to the medical oxygen outlet and related labeling in the United States?
- Blue
- Yellow
- Green (Correct answer)
- White
Correct answer: Green
Medical oxygen is designated green in the United States for all outlets, labels, and piping identification per NFPA 99 and CGA standards.
Question 5: What is the minimum distance NFPA 99 requires between a bulk liquid oxygen storage system and the nearest combustible construction?
- 5 feet
- 10 feet
- 25 feet (Correct answer)
- 50 feet
Correct answer: 25 feet
Bulk liquid oxygen systems must be located at least 25 feet from combustible construction to reduce fire and explosion risk.
Question 6: In a medical gas zone alarm system, what condition triggers a 'high pressure' alarm at the area alarm panel?
- Supply pressure drops 20% below the normal operating range
- Supply pressure rises 20% above the normal operating range (Correct answer)
- A zone valve is found in the closed position during normal operations
- A gas cylinder is nearly empty in the manifold supply bank
Correct answer: Supply pressure rises 20% above the normal operating range
A high-pressure alarm activates when the monitored zone pressure rises 20% or more above the normal operating pressure, indicating a PRV failure or over-pressurization.
Question 7: Which of the following tests is performed on medical gas piping after installation to verify system integrity before being placed in service?
- Hydrostatic pressure test with water at 1.5x working pressure
- Initial pressure test with oil-free dry nitrogen at 1.5x working pressure (Correct answer)
- Operational flow test using the intended medical gas
- Ultrasonic thickness measurement of all pipe joints
Correct answer: Initial pressure test with oil-free dry nitrogen at 1.5x working pressure
Initial pressure testing uses oil-free dry nitrogen at 1.5 times working pressure to verify leak-free integrity before introducing medical gases.
RMGA Medical Gas Systems Design & Components 4
When sizing a medical gas pipeline, what factor primarily determines the pipe diameter selected for a given branch?