Hach-Lange BODTRAK II: Respirometric Biochemical Oxygen Demand (BOD) - Manual (Page 9)

General information
9
2.2.2 Pressure sensor function
The BODTrak II is sealed to prevent external atmospheric pressure changes in the
test bottle. Pressure sensors monitor air pressure in the sample bottles. When
oxygen is consumed, the pressure in the bottle head space drops. The pressure
drop correlates directly to BOD.
2.2.3 Removing carbon dioxide
Carbon dioxide is made when microorganisms oxidize organic matter in the
sample. The carbon dioxide must be removed from the system so it does not
interfere with the measurement. Potassium hydroxide pellets put in the seal cup of
each sample bottle before the test remove the carbon dioxide.