Recently we had a client ask if he could use SODASORB® as an alternative to compressed nitrogen for calibrating a CO2 sensor.
SODASORB® absorbent is intended for use in anesthesia circle systems and respiratory therapy equipment for the purpose of removing exhaled carbon dioxide. SODASORB® makes it possible for intended in-line gases to be rebreathed by the patient. As it absorbs carbon dioxide, a dye added during manufacture changes color so you can tell when it must be replaced.
We have had customers put SODASORB® in a condenser tube and push or pull air through it with a small pump to achieve low CO2 air for calibration. While SODASORB® is fine for this purpose, it is not perfect. From our observations, 10-20 ppm (parts-per-million) of CO2 will remain in the gas after being passed through the absorbent. Therefore, if using SODASORB® for calibration, you will have to bias your baseline. For example, you could first calibrate using nitrogen, then measure air passed through SODASORB®, and record the CO2 level difference in ppm. The difference would be then used to bias your recorded data.