CIRAS-3 Operation Manual V. 1.09  168  support@ppsystems.com 
 
It is taking longer than normal for my CO2r levels to settle 
•  Under settings your CO2 Reference is likely set to “Fixed analysis air”.  Change to “Fixed 
reference air”. 
I am unable to achieve a Max C calibration above 2000 ppm and it is failing 
•  Your CO
2
 cartridge is low and needs to be replaced. 
•  Your desiccants are exhausted and require replacement.  Replace all desiccants. 
H
2
O Measurement and Control 
My H2Or levels are reading higher than expected 
•  There may be a leak somewhere in the gas circuit allowing external ambient air into the system.  
Usually this is associated with the absorber columns and the result of a recent desiccant change.  
Check that both absorber column assemblies are firmly fitted to the CIRAS-3 console and check 
all “O” rings to ensure that they are all firmly seated and not pinched off or cracked. 
•  Exhausted H
2
O scrubber in the Zero column.  Check the Drierite and replace. 
 My H2Or levels are reading lower than expected 
•  Exhausted H
2
O scrubber in the Zero column.  Replace the Drierite and Molecular Sieve. 
My H2Or or H2Oa values are fluctuating 
•  First I would check your desiccants and change out if exhausted. 
•  There may be a leak somewhere in the gas circuit allowing external ambient air into the system.  
Usually this is associated with the absorber columns and the result of a recent desiccant change.  
Check that both absorber column assemblies are firmly fitted to the CIRAS-3 console and check 
all “O” rings to ensure that they are all firmly seated and not pinched off or cracked. 
•  Your reference or sampling pump might be dirty or dusty and require cleaning or replacement.  
See Servicing the Air Sampling Pump (Reference & Analysis). On page 181
.  Another quick trick 
is to simply swap the pumps to see if the problem follows the pump. 
•  Dirty air supply unit hydrophobic filter.  See Air Filters on page 183 for more details. 
My H
2
O readings are drifting 
•  Exhausted H
2
O scrubber in the Zero column.  Replace the Drierite and Molecular Sieve.