The PPM of Co2 in my room match my PPM in my food. My food schedual is very strong. My strength of food goes up every week and my Co2 as well. I was told a long time ago for your Co2 to work best the PPM of Co2 should match your PPM in your food. I have allways used Co2 so I couldnt tell you what the difference is compared to not using Co2.