The Effect of Humidity Level on the Efficiency of Carbon Dioxide Absorption by Soda Lime

Soda lime - Ca(OH)2 - is a substance used in many different situations to absorb carbon dioxide - CO2. Soda lime is used in closed circuit breathing systems to remove CO2 and recycle unused oxygen back into the system. These breathing systems can be found in diving rebreathers and anesthetic breathing machines. An innate dilemma with soda lime is that it must be replaced quite frequently, which can become costly.

This research experiment sought to determine if higher levels of humidity would lead to increased absorption efficiency of CO2 by soda lime. This was prompted by the fact that the absorption reaction involves water, H2O, and the idea that increasing H2O levels would increase the reaction rate. Data was collected by pumping a CO2/O2 mixture with varying humidity levels through a homemade soda lime filter and measuring the output CO2 level in parts per million.

The resulting data showed no sign of humidity having an effect on CO2 absorption efficiency of soda lime. An ANOVA test was run to look for any statistical significance in the data, and it came back with a 0.62 p-value, meaning that the data between the different humidity levels was very similar and within random variation of each other. Overall, the experiment has shown that humidity level does not affect CO2 absorption efficiency of soda lime.

Research Conducted By:

Evan Gonzales
Sterling Heights High School

Rachel Quesnelle
Warren Woods Tower High School