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4.5 Zero the Airway Pressure Gauge 
Stop manual or mechanical ventilation. Allow the breathing tube patient connection to open 
to the air. The airway pressure nears zero. If the pointer of airway pressure gauge fails to go 
to zero, the airway pressure gauge will indicate incorrect pressure. In this case, you need to 
zero the airway pressure gauge as follows   
1.  Stop manual or mechanical ventilation. Connect a breathing tube to the breathing circuit 
and let the breathing tube patient connection open to the air. Make sure that the folding 
bag fully collapses. 
 
2.  Remove the lens by digging out the lens buckle using a flathead screwdriver. 
 
3.  Adjust the zeroing screw using a small cross screwdriver to let the pressure gauge 
pointer go to zero.