tjandrews20

I am trying to do an experiment for my school's science fair where I, in part, measure how different atmospheric compositions effect plant growth, but I might of hit a minor roadblock and I was hoping someone could help me out. I was wondering if anyone knew of a device or method to measure the percent composition of different components of air, specifically oxygen and carbon dioxide, in a closed environment. So for example I would want to manipulate the environment so it was say, 5% CO2, but I need a device to measure when it gets to this 5% level. Any help would be greatly appreciated.