RELIABLE SOLUTIONS FOR CARBON DIOXIDE SUPPLY TO CELL CULTURE INCUBATORS
Incubators and Carbon Dioxide Cell culture incubators require carbon dioxide (CO2) to create the most favorable environment for cell growth. Unintended depletion of the carbon dioxide supply can significantly impair cell growth and viability. Due to the intermittent demand and unique properties of CO2, choosing the ideal supply system for incubators can be complicated. To ensure consistent and reliable CO2 supply to cell culture incubators, CONCOA offers specialized gas delivery solutions designed with materials best suited for carbon dioxide and tailored for large- or small-scale laboratory operations.
Determining Duty Cycle To properly size a laboratory supply system, estimating the daily demand for carbon dioxide and, in some cases, nitrogen (N2) is essential. This involves gathering the flow requirement for each incubator supplied from the same source during regular operation, recognizing that flow is non-continuous. Instead, the flow depends on the incubator’s “duty cycle,” which is directly related to the frequency and duration of door openings within 24 hours to remove or replace samples.
Typically, each incubator demands 6 liters per minute (lpm) of gas flow while injecting and has a static 0.08 lpm depletion rate at 5% chamber concentration. The CO2 will maintain the required 5 percent concentration inside the chamber, with a balance of air or N2 to limit the oxygen content. Gas flow is relatively short, and the demand is intermittent over time with incubator door openings and as the biological process consumes gas. Industry standards suggest active operations use a 30% duty cycle, while minimally active operations use a 10% duty cycle, with medium to large operations somewhere between. Table 1 highlights duty cycles and the daily and weekly amount of CO2 required per incubator to maintain optimal chamber concentration for cell cultures.
Materials of Construction When choosing a mode of supply, it is essential to consider the materials of construction for their compatibility with carbon dioxide, especially under high flow conditions, which cause a significant drop in temperature due to the Joule-Thomson effect. Elastomer diaphragms like EPDM (ethylene propylene diene monomer) will freeze under these conditions, causing them to lose flexibility and stop working. CONCOA gas delivery systems for carbon dioxide have 316L stainless steel diaphragms in every valve, ensuring reliable and consistent gas delivery. Additionally, many lab designers have concerns about brass components in incubator systems that supply cell growth, as brass is prone to corrosion and contamination. To this end, CONCOA offers brass and stainless steel equipment for all parts from source to point-of-use.
Single-Use Cylinder Applications One high pressure CO2 cylinder can efficiently supply an incubator when paired with a CONCOA 212 Series regulator and a 529 Series protocol station. The CONCOA 212 series regulator ensures precise pressure and flow control to the incubator chamber. Mounting the system securely on a fixed surface with a 529 Series protocol station helps maintain leak integrity by minimizing stress or movement that could cause leaks at the connections. Additionally, the 529 Series protocol station features an integral check valve at the inlet, which prevents backflow and contamination during cylinder change. This setup is ideal for small labs with limited space and resources running one incubator. However, regular monitoring and timely cylinder replacements are essential to avoid any disruption in the CO2 supply.
High Pressure Primary and Reserve Cylinder Supply CONCOA’s 526 CD Series semi-automatic pressure differential switchover with 308 Series heated line regulator delivers a continuous flow of carbon dioxide to cell culture incubators from a high pressure CO2 cylinder supply. When the cylinder pressure falls below a defined pressure range of 170 - 200 psig, signaling the primary cylinder is nearly empty, the system automatically switches to reserve without interrupting the gas flow. The 308 Series line regulator, equipped with three internal heaters at the seat, prevents the build-up of dry ice snow or crystals from clogging the system to maintain a smooth flow of CO2. Options include outlet and purge valves for pipeline isolation and purging after cylinder changeover. Integrating CONCOA’s 52 Series maniflex manifold system increases cylinder capacity to accommodate up to four cylinders per side, reducing the frequency of cylinder changeouts. While the 526 CD Series pressure differential switchover provides an uninterrupted gas supply, it does require operator reset of priority assignment when switching out a cylinder. However, upgrading to the fully automatic CONCOA AutoSwitch 2 significantly enhances system efficiency by permitting unattended system operation.
Laboratories Requiring Lights-Out Operation CONCOA’s AutoSwitch 2 changeover manifold with a state-of-the-art electronic actuator provides fully automatic switchover capability from primary to secondary high pressure CO2 supply without manual intervention. Advanced microprocessor control eliminates cylinder status guesswork by displaying whether a bank of cylinders needs replacing or is in use. Built with 400 Series high purity regulators and diffusion-resistant construction from inlet to outlet, the AutoSwitch 2 offers a helium leak integrity of 1 x 10⁻⁸ scc/sec. Fewer connections and integrated leak detection capability ensure safety from source to all use points. With real-time monitoring and remote access capabilities for streamlined operations, the revolutionary new AutoSwitch 2 is an excellent choice for automated bioresearch laboratories aiming to achieve consistent performance and operational efficiency when supplying CO2 from high pressure cylinders to cell culture incubators.
Continuous Incubator Operations Laboratories requiring 
more than four high pressure cylinders per week can benefit from switching to a cryogenic liquid CO2 supply delivered from CONCOA’s fully automatic IntelliSwitch™ II manifold switchover. The IntelliSwitch switchover manifold (Figure 2) is a versatile gas management system that works seamlessly with CO2 or nitrogen supplied from high-pressure cylinders or cryogenic dewars. It ensures continuous pressure and flow by automatically switching between primary and reserve cylinders as needed. Its electronic look-back feature uses a computer-controlled algorithm to achieve 97% primary cylinder utilization. The system switches back to fully draw down cylinder contents if the pressure in the former primary side increases. The economizer function further maximizes efficiency with 0% secondary cylinder vent loss. Remote monitoring capabilities allow real-time adjustments and troubleshooting for optimal performance. This combination of features makes the IntelliSwitch II the ideal mode of delivery for cell culture incubators, regardless of the gas source.
Piping and Point-of-Use Pressure Control Incubator piping should be sized to overcome pressure drop while maintaining adequate flow. For pipe runs greater than 25 feet, CONCOA recommends point-of-use regulation to control the final line pressure. Ideally, the manifold output pressure should be 50 psig higher than the equipment operating pressure. CONCOA offers the 304 Series point-of-use regulator or the 55 Series multiple outlet panel with 400 Series regulators for final line pressure control to reduce the source pressure to the required 6 to 15 psig. These options also allow for individual line isolation without disrupting the entire system. For new construction and existing laboratories, CONCOA engineers can customize systems to meet individual application requirements and specific laboratory or room constraints.
Laboratory Safety When using CO2 or N2 for incubator systems in laboratories, it is crucial to ensure the safety of personnel working in those areas. The CO2 piping system must include relief valves complying with local codes and safety standards such as NFPA 55. The relief valves on cryogenic liquid cylinders cannot be piped away and are exempt from this requirement, making safe storage and design particularly important. CONCOA 534 Series relief valves, strategically placed and piped to an appropriate exterior vent line, prevent over-pressurization. Gas usage and storage areas should incorporate CONCOA 580 Series air safety and oxygen deficiency monitors, which continuously check the air quality and trigger alarms if levels drop below safe thresholds. Integrated components, including CONCOA remote display, horn and strobe, and 585 Series emergency shut-off controller, form a comprehensive safety system that ensures compliance with safety standards and a safer environment for personnel.
To optimize monthly gas costs, CONCOA supports a variety of Equipment Solutions for the delivery of CO2 to cell culture incubators.