CO2 importance for seedlings/veg

I have heard that CO2 supplementation can be very beneficial during the flowering stage, but how about when the plants are seedlings or during veg growth? I have my stuff in my basement, and its about 25 ft. from my furnace, which runs on natural gas. I was wondering if the burning of the natural gas in the furnace creates enough co2 for the room? I have fans blowing on my seedlings to keep the air moving but didn't know if I needed to get some excellofizz for the growth stage, or to just get it when i'm ready to flower. Thanks!

Bump.

I also would like to hear the answer to this.

Perhaps, once dangerousdiggity's question is answered, we could turn this into a thread about different methods of getting CO2 into the grow. Me, I'm growing in a stealth box, and I'd love to know what I could do to help my plants