RMGA System Testing 2 — Questions and Answers
Question 1: What is the minimum pressure used during a high-pressure leak test of a medical gas pipeline system per NFPA 99?
- 50 psig
- 100 psig
- 150 psig (Correct answer)
- 200 psig
Correct answer: 150 psig
NFPA 99 requires a high-pressure leak test at 150 psig (or 20% above the system's maximum operating pressure) for medical gas pipelines.
Question 2: During a cross-connection test, all zone valve boxes are closed and a test gas is introduced. What should the reading be at each outlet if the system is free of cross-connections?
- A positive pressure reading at every outlet
- Zero pressure at every outlet in the zone being tested (Correct answer)
- Atmospheric pressure only at the zone being tested
- No flow when tested with an oxygen analyzer
Correct answer: Zero pressure at every outlet in the zone being tested
With zone valves closed, pressure should be zero at all outlets in the isolated zone if there are no cross-connections feeding gas from another source.
Question 3: Which gas is typically used to perform the initial pressure test of a newly installed medical gas pipeline before purging?
- Oxygen
- Nitrogen (Correct answer)
- Carbon dioxide
- Medical air
Correct answer: Nitrogen
Dry nitrogen (or oil-free dry air) is used for initial pressure testing because it is inert, non-flammable, and avoids introducing combustion-supporting gas into an untested system.
Question 4: When conducting a standing pressure test on a medical gas system, how long must pressure be maintained without loss to pass?
- 10 minutes
- 20 minutes
- 24 hours (Correct answer)
- 72 hours
Correct answer: 24 hours
NFPA 99 requires the standing pressure test to be maintained for a minimum of 24 hours without pressure loss to confirm the integrity of the piping system.
Question 5: What does a positive result on an odor test during medical gas system verification indicate?
- The system passed and is ready for use
- Contamination is present in the pipeline (Correct answer)
- The gas is medical grade oxygen
- The zone valve is properly sealed
Correct answer: Contamination is present in the pipeline
An unusual odor detected during outlet testing indicates contamination such as oil, solvent, or purge gas residue still present in the pipeline.
Question 6: During a pipeline purity test, what maximum level of contamination (particulate) is generally acceptable for a medical gas system?
- No visible particulate on a white filter paper after 30 seconds of flow (Correct answer)
- Less than 1 mg/m³ measured by gravimetric analysis
- Less than 5 ppm by volume
- Less than 10 microns particle size
Correct answer: No visible particulate on a white filter paper after 30 seconds of flow
NFPA 99 requires that no discoloration appear on a white filter after flowing gas through it for 30 seconds, confirming freedom from particulate contamination.
Question 7: Which of the following best describes the purpose of the 'piping purge' step performed before final system testing of a medical gas pipeline?
- To pressurize the system for leak testing
- To remove debris, moisture, and residual test gases from the pipeline (Correct answer)
- To verify correct gas identification at each outlet
- To calibrate the pressure alarm setpoints
Correct answer: To remove debris, moisture, and residual test gases from the pipeline
Purging blows high-velocity gas through the pipeline to physically remove construction debris, moisture, and any residual gases before purity and cross-connection testing.
RMGA System Testing 2
What is the minimum pressure used during a high-pressure leak test of a medical gas pipeline system per NFPA 99?