Here is a little info I found that might help you buddy.
DRY ICE METROD OF CO2 ENRICHMENT: This method works well for small areas, especially if some cooling effect is desired. Dry ice, solid carbon dioxide, is very coldóabout 109 degrees F below zeroóso we suggest you handle it with gloves. Dry ice is available through freezer and meat packing outlets and is relatively inexpensive. In our std. 8' X 8' X 8' room, you would need about 0.8 lbs. of dry ice per day to raise the atmospheric CO2 content to 1300 parts per million. If the growing area is quite warm, 0.8 lbs. can melt much faster than 12 hours. Two methods can be used to regulate this. One is to cut just small pieces, about .1 lb., and add a new piece every two hours to the growing area. The second method is to put the required amount in an insulated styrofoam box with a few small holes cut in it. This will slow the rate of melting considerably but must be "tuned in" to get it just right so 0.8 lbs. melts in the 12 hours of light "on" time. Extra dry ice must be kept in a freezer to prevent loss due to evaporation.
Since CO2 is heavier than air, one good method of distributing it to the plants is to attach the container or dry ice to the light reflectors which are normally placed over the plants. The CO2 will then flow down through or over the lights and evenly bathe the plants. If a circulation fan is used, the dry ice or its container should be placed directly in front or behind it for even distribution. Common to all CO2 enrichment methods, try to seal up the room or greenhouse as best you can, especially around the bottoms of doors and walls.
The dry-ice method will cost around 60 cents per day for our standard sized, 512 cu. ft. grow room. A possible benefit of using dry ice is the cooling effect it produces.