To find out how much C02 is needed to bring the growing area
to the ideal 2000 PPM, multiply the cubic area of the growing room
(length x width x height) by .002. The total represents the number
of square feet of gas required to reach optimum C02 range. For in-
stance, a room 13' x 18' x 12' contains 2808 cubic feet: 2808 x .002
equals 5.6 cubic feet of C02 required. The easiest way to supply the
gas is to use a C02 tank. All the equipment can be built from parts
available at a welding supply store or purchased totally assembled
from many growing supply companies. Usually tanks come in 20
and 50 pound sizes, and can be bought or rented. A tank which
holds 50 pounds has a gross weight of 170 pounds when filled.
A grow room of 500 cubic feet requires 1 cubic foot of C02
A grow room of 1000 cubic feet requires 2 cubic feet of C02
A grow room of 5000 cubic feet requires 10 cubic feet of C02
A grow room of 10,000 cubic feet requires 20 cubic feet of C02
To regulate dispersal of the gas, a combination flow
meter/regulator is required. Together they regulate the flow bet-
ween 10 and 50 cubic feet per hour. The regulator standardizes the
pressure and regulates the number of cubic feet released per hour.
A solenoid valve shuts the flow meter on and off as regulated by a
multicycle timer, so the valve can be turned on and off several times
each day. If the growing room is small, a short-range timer is need-
ed. Most timers are calibrated in hour increments, but a short-
range timer keeps the valve open only a few minutes.
To find out how long the valve should remain open, the
number of cubic feet of gas required (in our example 5.6 cubic feet)
is divided by the flow rate. For instance, if the flow rate is 10 cubic
feet per hour, 5.6 divided by 10 = .56 hours or 33 minutes (.56 x
60 minutes = 33 minutes). At 30 cubic feet per hour, the number of
minutes would be .56 divided by 30 x 60 minutes = 11.2 minutes.
The gas should be replenished every two hours in a warm, well-
lit room when the plants are over 3 feet high if there is no outside
ventilation. When the plants are smaller or in a moderately lit
room, they do not use the C02 as fast. With ventilation the gas
should be replenished once an hour or more frequently. Some
growers have a ventilation fan on a timer in conjunction with the
gas. The fan goes off when the gas is injected into the room. A few
minutes before the gas is injected in the room, the fan starts and
removes the old air. The gas should be released above the plants
since the gas is heavier than air and sinks. A good way to disperse
the gas is by using inexpensive "soaker hoses", sold in plant
nurseries. These soaker hoses have tiny holes in them to let out the
C02.
The C02 tank is placed where it can be removed easily. A hose
is run from the regulator unit (where the gas comes out) to the top
of the garden. C02 is cooler and heavier than air and will flow
downward, reaching the top of the plants first.
