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principles of carbon dioxide enrichment


CO2 will dramatically increase the growth of green plants. Green plants use carbon dioxide (CO2) and water in the presence of light to synthesize organic compounds. The plant then converts these organic compounds into elements that it can use (food). This process is called photosynthesis. If any of these ingredients (CO2, water or light) are at levels below what the plant can use for maximum efficiency, it will only be able to perform at that level and no greater. Adding carbon dioxide to a growing environment that is not receiving proper nutrients or is low on light will not produce the desired results. Similarly, plants that are receiving plenty of sunshine and nutrients will only perform as well as the ambient level of CO2 will allow. The ambient level of CO2 in the earth's atmosphere is generally between 300 and 600 ppm. Most plants receive far more water and energy in the form of sunshine than they can use. Increasing the CO2 in the growing area will let the plant use the excess water and energy that is stored in the leaves. The result is a substantial increase in the growth rate of any plant that uses chlorophyll in the process of photosynthesis. Enrichment should commence at sunrise or when photoperiod begins and refrain during darkness hours. The average CO2 level that is recommended is 1000 to 2000 parts per million (PPM). The object is to maintain a constant level in the atmosphere. You can run a small unit continuously during photoperiods or you can use a larger unit and time it to function periodically. Where exhaust requirements are frequent, the latter method is preferable. After the exhaust function the generator can be cycled to replenish CO2 quickly to maintain rapid plant photosynthesis. Use the operation time charts to determine the size of generator and the number of minutes of operation required for the level of CO2 desired. Frequency of recharge depends on the rate of consumption. For the greatest fuel economy and accuracy of recharge it is recommended that the Green Air Products CO2 Monitor Controller (CDMC) be used with all generator and emitter systems.


Carbon dioxide generators operate by burning carbonaceous fuels such as propane or natural gas. The burners used in Green Air Products CO2 generators are specially designed to maximize the production of CO2 and minimize heat as a by-product. Green Air Products generators provide CO2 far more economically than any other means of enrichment. An electronic igniter is used to strike a flame when the generator is turned on. If the burner flame is lost the valve will close so that unburned fuel will not be released into the enclosure. CO2 Generator operations may be automatically functioned according to actual ambient values when installed in conjunction with the SPC-1 or CDMC CO2 controllers. This control device continually samples the level of carbon dioxide in the growing area and functions the generator whenever CO2 levels do not meet your predetermined values. Generators are easily installed, dependable and efficient. Transformer included. Operates on 110 VAC

Green Air Products offers an assortment of models to fit any size enclosure. Use the links below to choose the model best suited for you needs.

All models include: 120/12VDC 6W 1 amp power transformer with 2.1 mm plug, 10 ft. 3/8 ID fuel hose, propane small appliance gas pressure regulator, fuel line fitting for connect to NG supply, and ceiling mount hardware kit. Propane tank not included. No regulator required for NG installation. Air cooling tube for the IR models is an optional accessory. See timers and CO2 monitors for controller options. See LPCV propane tank crossover valve for handy accessory.

CO2 is a little heavier than air but only when it is cold. Hot CO2 emissions go straight to the ceiling instantly and stay there until they cool, and up there they may never cool enough to get mixed in properly with your plant zone atmosphere. You need to sit back and think about your grow room atmosphere and where your CO2 is going. If you just let it go wherever you will not be optimizing your enrichment and will be wasting CO2 and creating unnecessary heat.
The idea is to get the CO2 emission properly diluted and directed into your air mix. I get many calls from people who think the generator is not producing CO2 but actually that is impossible. If it is burning a clean flame it is producing the amount of CO2 we say it is. That is just the law of physics. You burn a given amount of propane or natural gas you get a resulting ratio of CO2 and BTU. It does not matter how you do it or how fast you do it, it will always be the same ratio of CO2 and BTU per fuel. This of course is assuming it is a proper flame and a complete combustion. If the flame is not proper you will see yellow in the flame that indicates either a contaminated fuel or improper air/fuel mix. An incomplete burn will produce CO carbon monoxide which we all know is not good.
Green Air Products generators have always been designed to produce a clean and complete burn providing the best combustion for maximum CO2. Our new infrared burners are especially efficient at providing a pure conversion of fuel. That is because of the extremely compact low profile of the flame on a large ceramic surface.
Infrared waves are electromagnetic radiation which is a spectrum of light much like the light put off by the sun. It does not transfer heat until it hits an object. That is why radiation can travel from the sun 100 million miles to earth and still provide heat. The infrared burner in your generator turns its radiant energy into infrared and provides that this heat can be transferred to the aluminum heat sink and then carried away by exhaust. Less heat is transferred to the air in your atmosphere as a result.
Place or suspend your generator anywhere that is convenient. It is preferable that it is not too close to an exhaust vent. The idea is to direct the hot emissions from the generator out into your enclosure where it will be involved into your air circulation. It is recommended that you place a fan above and offset to one side so it is gathering the emissions and broadcasting it out into the room. It is also suggested that you place fans at a few locations near the ceiling blowing the ceiling air directly down into the plant canopy. This will keep the CO2 from collecting at the ceiling and assure an even distribution of atmosphere throughout the enclosure. A consistent atmosphere is important to the plants for many reasons. All of your atmospheric controls will work together much more efficiently.
A CO2 monitor is a very important tool in maximizing CO2 benefit. To be effective your plants need a consistent continuous supply of CO2 during their photoperiod. A CO2 monitor will pay for itself in conservation of fuel and heat as well as yield. When choosing the size of generator for your enclosure realize that once your enclosure is charged with CO2 the generator may only come on for a minute or two as required to top off the enrichment level. 1000 ppm is a very adequate level to maintain for optimum growth. Calculate your cu/ft of room size LXWXH. The IR-28 takes 2 minutes per 1000 cu/ft to produce 1000 ppm CO2. The IR-42 takes 1.5 minutes per 1000 cu/ft to produce 1000 ppm CO2. If your generator is running longer or more frequent then is expected you must be losing it somewhere or not have your circulation optimized.
One of the unique features of the Green Air IR generator is the air cooling capability. While this is a popular option I must bring up a few points. If the generator is only running for a couple minutes every so often it is not likely that cooling is necessary. Realistically in a short operating period the heat exchanger will not have enough time to collect and remove much heat. Some larger installations where the generators are operating for longer periods (10 minutes or more) at a more frequent schedules air cooling can be a significant advantage. My recommendation is unless you are certain try it without the cooling and then make a decision.


Plants need oxygen for many of their processes. This is usually provided by fresh air ventilation. These days it is popular to try and use sealed rooms. While this seems like a nifty idea it poses some problems with oxygen supply. CO2 generators also need oxygen for the flame to burn properly. If oxygen becomes deficient the flame will not have a complete burn and CO2 will not be efficiently produced. Yellow or weak flame is an indication that the burn is not correct. The fuel to air mixture is not proper. This will create CO carbon monoxide which is harmful to animals, however not to plants. Ethylene gas is a minor by-product of burning carbonaceous fuels such as LP and NG. While this gas is in very small quantities it could build up in a non-vented enclosure. With the lack of oxygen the ratio of oxygen and ethylene becomes more critical. Ethylene is thought of as the aging hormone in plants. In addition to causing fruit to ripen, it can cause plants to die. Ethylene will cause a wide range of effects in plants, depending on the age of the plant and how sensitive the plant is to ethylene. Ethylene effects include fruit ripening, loss of chlorophyll, abortion of plant parts, stem shortening, abscission of plant parts, and epinasty (bending of stems). Do not underestimate the importance of maintaining a proper atmospheric balance and good circulation in your enclosure.

Do not be discouraged because many growers are having great success using generators in primarily sealed rooms as long as they keep in mind these basic essential requirements. We get calls from time to time and people think the generators are killing their plants. That is simply not the case if they are being used properly. Also keep in mind that CO2 enrichment accelerates the plants metabolism. If the plant is stressed or on the brink of some other deficiency or disease this could throw the plants over the edge. Remember that when a plants metabolism is increased its demand for water, fertilizer, and light are also increased. CO2 is only part of the ratio of the plants essential requirements. Any one of them can become the limiting factor and render the others ineffective.