Measuring CO2

Marijuana Horticulture

by Jorge Cervantes

Measuring and monitoring CO2 levels in the air is rather expensive and often unnecessary for small growers. Monitoring CO2 levels in grow rooms with ten or more lights really helps keep the levels consistent.

Disposable comparative colorimetry CO2 test kits are easy to use, accurate, and inexpensive. The test kits contain a syringe and test tubes and sell for about $30. To use the kit, break off each end tip of the test tube, and insert one end into the closed syringe. Pull 100 cubic centimeters into the syringe, and note the blue color change in the cylinder where the active ingredient reacts with the CO2 in the air drawn through the cylinder. These kits are reliable to within 40 ppm.

Electrochemical sensing systems measure electrical conductivity of an air sample in either an alkali solution or distilled or deionized water. These systems are relatively inexpensive, but they have drawbacks: limited accuracy and sensitivity to temperature and air pollutants.

Infrared monitoring systems are more accurate and versatile. They correctly measure CO2 and can be synchronized with controllers that operate heat, ventilation, and Co2 generators. Even though the initial cost for a monitor is high, they can solve many CO2 problems before they occur and can ensure optimum growing conditions. Specialty indoor garden stores sell the monitors for less than $1000.

Growers who do not want to spend the time and energy required to monitor CO2 can use a set of scales and simple mathematics to determine the appropriate amount of CO2 in the air, but this calculation does not account for ventilation, air leaks, and other things that could skew the measurement. It is easier to measure the amount of CO2 produced rather than to measure the amount of CO2 in the grow room’s atmosphere.

To measure the amount of fuel used, simply weigh the tank before it is turned on, use it for an hour, and then weigh it again. The difference in weight is the amount of gas or fuel used.