Evaluating CO2
requirements
The fi rst step in any properly sized laboratory or facility’s gas requirement is to determine the daily demand for that gas. If this involves an existing ongoing operation, it would begin by totaling the amount of gas containers onsite and considering how many are delivered each week or month to start with a baseline of what your facility has on hand in total gas in use and that held in reserve. From that information, you can determine the total gas on hand using the information in Table 2, which gives the average full contents of both high-pressure and cryo- genic liquid cylinders in pounds of net content converted to liters of gas at standard tem- perature and pressure. This can be compared to what the expected daily consumption of gas should be once you evaluate each use location for the entire facility. From this you can deter- mine whether to consider changing the gas delivery system and form of supply, and if you can reduce the amount of CO2
unnecessarily released through venting to become a greener
Table 2 – Average full contents of both high-pressure and cryogenic liquid cylinders in pounds of net content converted to liters of gas at standard temperature and pressure (STP)
Cylinder Lbs of CO2
Cu ft of gas at STP Gaseous liters at STP
50 lb HP 160 L 50
375 438 12,403 3285 93,021
laboratory. For new operations, each use loca- tion should also be evaluated to determine the total expected daily requirement for CO2
. From
this, the best gas delivery system and form of delivery can be determined.
In the case of CO2 for cell culture incubators
or bioreactors, you should evaluate the fl ow requirement during normal operation. For cell culture incubators, this requirement is typically expressed in liters per minute (lpm) of CO2
fl ow
at 6 lpm for each incubator chamber. Keep in mind a dual-stack incubator would be twice this rate when counting the number of incubators. However, the CO2
to cell culture incubators,
180 L 414
3626
230 L 516
4520
260 L 615
5387 102,677 127,993 152,543
though required to be uninterrupted, is not a continuous 24/7 fl ow. The CO2
is used to
maintain the required concentration inside the chamber at typically 5% with the balance being air or, in some cases, a reduced ambient level of oxygen content by also injecting nitrogen to lower the oxygen content. The CO2
concentra-
tion only changes when the incubator door is opened, exposing the chamber to ambient air with very little CO2
content (<400 ppm).
Once the door is closed, the incubator’s CO2 monitor detects that lowered concentration and actuates a solenoid to allow more CO2
to fl ow into the chamber to return the concentration
AMERICAN LABORATORY • 23 • SEPTEMBER 2013
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