Hi,
Generally, the ppm of CO2 in the air is around 300. Optimal PPM for CO2 in a sealed grow room is 1500. The amount of CO2 you exhale is minimal and unfortunately will not make much of a difference, especially if your grow room is not air-tight. If you want to increase CO2 PPM levels, you need to seal your room as much as possible to prevent air from being cycled with outside air. Then, you have a few options as to how to increase the CO2 levels (yeast, dry ice, CO2 tanks).
I noticed that you live in boulder. If you need any advice/help, there's an awesome grow store in gun barrel (63rd & lookout) with very knowledgeable staff. Hope this helps!
-AR