Yes, mushrooms do give off CO2 (carbon dioxide) as part of their metabolic processes. Like all living organisms, mushrooms consume oxygen and release carbon dioxide as a waste product during respiration. This process occurs continuously in mushrooms, just as it does in other organisms, meaning that they will always be releasing some amount of CO2 into their environment. However, the amount of CO2 released by mushrooms is generally quite small compared to that released by larger organisms like humans or animals. Additionally, mushrooms are also capable of absorbing some of the CO2 in their environment through a process called photosynthesis, which can help to offset their own CO2 emissions to a certain extent. Overall, while mushrooms do release some amount of CO2, they are not a major source of greenhouse gas emissions compared to other sources like fossil fuels or industrial processes.