Clean way to add extra Co2?

[cigarettes42]

I tried baking soda and vinegar in the past and it made a merry mess. Still, when growing with LED's you need :

• more heat
• more Co2
• less water
• less nutes

My current cabinet is much smaller- 2' X 1' X 4' 8". and has an active air intake (camouflaged by a kitty litter box) so...what's a clean, safe way to increase Co2 levels? Does it really matter for such a small grow (2 plants in a small cabinet)?

if its just 2 plants i would just make sure you have a lot of air moving in and out. co2 is beneficial but with only 2 plants, you are going to be paying a lot. easy way is getting a tank of co2 with regulator and timer. but if you wanted to do a cheaper way is dry ice. put it in a bucket and direct it to your intake. but it will cost a lot in the long run cause the constant exhaust will just suck it right out and you would have to keep buying dry ice. imo 2 plants will do fine without it, if you have good air flow