After builindg it I did 3 tests. I measured the ambient CO2 levels, the amount of CO2 produced by the BBQ, and the CO2 levels after the filter.

I started with the baseline measurment of the ambient CO2 levels. I calibrated the CO2 monitor and got a measurment of 521ppm.

For the next test, I lit the barbecue and detatched the carbon fitler. After a few minutes the CO2 levels jumped to 3988ppm.

Then to capture the CO2 I reatatched the carbon filter and after a few minutes the CO2 levels reduced to 546ppm.