This means that you need to get rid of any possible air leaks when the grow space is closed. The only air getting in or out should be the air moving over your grow lights. You will keep this air segregated from your grow space by using ducting hooked up to the right type of reflector. In some cases, instead of an open room with batwings, growers will keep the air blowing over the lights completely separate. Cooltubes can keep your plants and grow lights cooler by trapping air and allowing it to be easily exhausted.
They are suitable for CO2 enrichment because they let you exhaust heat from your grow lights without letting outside air touch your grow space. Some cooltubes even come with an extra large reflector, which directs even more light down to your plants. Air-cooled hoods have piece of glass or plastic which keeps hot air contained near the bulb (and away from your plants). These would be used in the same situation as the cooltubes, though these usually are more effective at reflecting light downwards. Many air-cooled hoods (like the one pictured here to the right) have the ability to be hooked up to ducting on both ends, which allows these hoods to be used for CO2 enrichment. In other words, after you’ve sealed your grow room away from your lights, you can set up an intake and exhaust fan to blow air cool over the lights and have an exhaust fan vent out the hot air without also venting out all your CO2. Once you get your reflector, use ducting to allow air in and out of the sealed grow space, with the grow light & hood in the middle to rain light down over your plants. You should maintain high temperatures, between 85°F (30°C) and 95°F (35°C).
When you’re adding CO2, especially higher amounts, you will get the best results at higher temperatures. Normally you want your garden to be a comfortable room temperature, but when adding CO2 at very high levels, you want to keep temps above 85°F (30°C). Many growers recommend you keep temps as high as 95°F (35°C) when maintaining CO2 levels around 1200-1500 PPM. If the temperature is lower than 85°F (30°C), you won’t seeas much benefit from adding CO2. However, since you must seal your grow room to keep all the CO2 from escaping, it'll likely be easy to keep temps that high when you're running your grow lights. For growers supplementing smaller amounts of CO2, it isn't recommended that you specifically try to raise the temperature of your grow space, but the CO2 can help protect your plants from heat and light stress. No matter what, watch plants closely for signs of heat stress and react accordingly! 3.) Add CO2 By "Raining" It On Your Plants From Above. CO2 should “fall” onto plants from above if possible. CO2 is heavier than air and will sink to the bottom of your grow area, so you you want your CO2 to float down onto your plants. That means any CO2 enrichment method should be located above your plants. You’ll get the best results when you make sure CO2 is evenly dispersed over your plants. A small fan on the floor pointed upwards can help keep the CO2 circulating through the room and floating over your plants. There are 6 popular ways of adding CO2 to the air of your grow area… CO2 Generator 4.) Turn off CO2 at Night. Plants actually stop "breathing in" CO2 at night, so you can turn off your CO2 enrichment system when the lights go out! Save money by having your CO2 enrichment turn on a half hour after your lights do, and turn off a half hour before your lights turn off. In other words, have your CO2 off for about an hour longer than your dark period. This will save you many hour’s worth of CO2 injection each day and in tests has proven this will not affect the CO2 effectiveness. 5.) How to Use CO2 in the Vegetative Stage & Flowering Stage. In this section we'll cover exactly how CO2 affects marijuana growth at different stages of life, and what you can do to maximize your growth and yields. CO2 is most effective at increasing the speed of vegetative growth, so adding extra CO2 is a great way to grow bigger plants in less time during marijuana’s vegetative stage of growth. In the vegetative stage, just keep CO2 going during daylight hours, raining down over your plants. Almost all growers seems to agree that you can get increased growth and bud production by running CO2 during the first 2-3 weeks of flowering. After flowering is fully underway, some growers believe that CO2 is less effective, and it’s true that so far no one has been able to prove that CO2 can directly improve bud production beyond the first few weeks of the flowering stage. However, a lot of growers feel from personal experience that running CO2 does increase bud production.
Some growers recommend that you keep running CO2 all the way until 2 weeks before harvest.
There are a variety of ways to add CO2, some of which are better than others! A CO2 generator burns propane, ethyl alcohol or natural gas to produce CO2 for your grow space. (as long as you use a CO2 generator with safety features) Many of these can be hooked up to a monitor for no-worries, automatic CO2 enrichment.