3. Low-Pressure System

3.1 Check initial status of low-pressure system

• All vaporizers correctly installed
  • Vaporizers are full and fill ports closed
  • Tops of vaporizers are parallel to manifold - cannot be lifted off manifold
  • Only one vaporizer turns ON at a time

• overfilling of vaporizer
• vaporizer not locked on to manifold
• faulty interlock mechanism - can turn on two vaporizers simultaneously
• vaporizer will not turn ON - interlock obstructed by ECG lead, etc

3.2 Perform low-pressure leak test

• Verify master switch OFF, vaporizers OFF
• Do leak test with "suction bulb" device on common (fresh) gas outlet
  • Verify bulb stays collapsed for > 10 secs

• defective suction bulb
• leak somewhere between flow control valves and common gas outlet
• cracked, loose, misaligned flow tubes
• loose connections - piping, components

• Repeat leak test for each vaporizer, one at a time - setting dial to 1% conc.

• partially open filler/drain port
• missing port O-ring on manifold

• Verify all vaporizers OFF, fresh gas hose reconnected, and flush system with O₂

3.3 Turn ON gas machine master switch

• O₂ supply failure alarm activated
• Electrical mains light activated and battery fully charged

• alarm mechanism malfunction
• battery discharged because machine left ON and unplugged to AC outlet

3.4 Test flowmeters

• Minimum flows are 20025 ml/min for O₂ and zero ml/min for other gases

•  
• no flow - broken tip of needle valve

• Flowtubes are undamaged; floats move smoothly throughout their full range

• floats sticking - dirt, grease, static
• float stuck at top of flow tube
• stop broken off from top of flow tube and resting on float

• You cannot set the O₂ and N₂O flow controls to supply hypoxic flowrates

• N₂O/O₂ 3:1 proportioner - linkage broken or gear stop misaligned

• Low O₂ pressure stops other gas flows
  • Set floats to mid-range - disconnect O₂ pipeline - push O₂ flush
  • O₂ supply failure alarm sounds and Air and N₂O floats drop

• no low O₂ supply alarm at 30 psig
• shutoff valves fail to close at 20 psig

• Turning ON vaporizer does not lower gas flow

• obstruction in vaporizer or manifold