CO2 incubators are essential for biological work. By very precisely regulating CO2, humidity and temperature, incubators create the ideal environment for cell and tissue work. While there are many types of incubators suited to various applications, CO2 incubators are ubiquitous in the biological/chemical laboratory, especially if cell/tissue cultures are routine work.
Size: Benchtop, Floor-standing, Reach-in
When looking to purchase a CO2 incubator, the first feature to consider is size—both internal volume and external bench—although they do go hand-in-hand more often than not. Major manufacturers boast a variety of volume sizes, typically from 1 cubic foot to 10 cubic feet and much beyond. To determine which model is right for you, ask yourself a few questions about your lab’s everyday use of incubators. For example:
- How many experiments do you need to run simultaneously?
- How many dishes/flasks do you need to fit in one incubator at a time?
- Do you need to place additional equipment, such as a shaker, inside your incubator?
The answers to these questions will help personalize your equipment selections, but here are some general guidelines. Benchtop models, which go up to about 6 cubic feet, are excellent for use by one or two researchers. Depending on the manufacturer, these models are sometimes stackable. Floor-standing incubators are larger and therefore better suited for multiple researchers, allowing them to isolate different cultures within the same unit for a variety of studies. Reach-in incubators are ideal for high-volume labs. These incubators, which range from 11 cubic feet to over 30 cubic feet, can accommodate additional equipment. The many internal racks also allow researchers space between experiments, when necessary.
Temperature Control: Water, Air, Direct Heat
CO2 incubators employ three main types of temperature control: water-jacketed, air-jacketed and direct heat. In a water-jacketed incubator, the growth chamber is surrounded by water, which is warmed through heating elements. The water circulates via convection, exchanging heat with the growth chamber and acting as a thermal buffer. Compared to air-jacketed and direct heat incubators, water-jacketed models provide a higher level of temperature accuracy and uniformity, but—since they are filled with water—are extremely heavy and hard to move. If you need to empty one out and move it for any reason, it can take up to a day to reestablish an optimal operating temperature.
Air-jacketed incubators, on the other hand, are lighter and faster to set up than their water-filled counterparts since the walls are filled with air. However, since air has a smaller heat capacity than water, air-jacketed incubators are more sensitive to changes in temperature, which can be an issue if the incubator is subject to frequent door openings. That being said, air-jacketed incubators, like direct heat models, are suitable for high heat sterilization and temperatures exceeding 180°C, something not achievable with water-jacketed incubators.
Direct heat incubators surround the growth chamber with heating elements, be it through convection or with the assistance of a fan. Since the inside is heated directly, recovery time for direct heat incubators is much faster than a water-jacketed model. However, for those that rely on fans, the resulting vibration can have negative effects on some sensitive cells. Like air-jacketed incubators, some direct heat models use humidified or dry-heat cycles to high-heat decontamination and sterilization.
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Decontamination: High Heat, H2O2, UV Light
Almost all CO2 incubators feature some type of contamination control, be it a high-temperature sterilization, HEPA filters or the use of anti-microbial copper surfaces in the growth chamber. But, not all CO2 incubators boast specific decontamination features. Models with decontamination technology are typically more costly, so budget is something to be considered when evaluating the need for such an incubator.
Wet/dry high heat decontamination is a common method to ensure the integrity of the growth chamber inside CO2 incubators. Often run overnight since it takes about 8 hours to complete, the process raises the interior temperature of the incubator to 180°C, eliminating most contaminants. However, certain organisms, like Staphylococcus aureus, have been shown to withstand this high of a heat. That’s one reason the use of hydrogen peroxide vapor decontamination (H2O2) is becoming an increasingly popular alternative.
Effective and environmentally friendly, H2O2 completely eliminates a wide variety of contaminants, including mycoplasma, bacteria, viruses, spores and more. H2O2 also has the benefit of a shorter run-time: you only need about 3 hours to completely decontaminate your incubator—meaning decontamination can occur within the workday if absolutely necessary.
PHC, a leader in the field, employs patented SafeCell UV technology as a decontamination method in some of its incubator models. SafeCell relies on a programmable ultraviolent light emitting a 253.7 nm wavelength to kill all airborne contaminants. The decontamination process runs continually with the door closed, meaning decontamination occurs in 1-to-30-minute cycles throughout the day, but it can be programmed with an overnight option.
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Monitoring: Internal versus External
Given the function of incubators, it’s vitally important for conditions such as temperature, humidity and CO2 to be maintained at desired levels at all times. If that doesn’t happen for whatever reason, it’s also vitally important that you, the researcher, is notified your incubator is/was out of parameters—the success of your experiment depends on it.
Most incubators come with built-in IR sensors and alarms that alert when a condition is out of parameter. A basic alarm functions much like a household alarm—it will alert the researcher to the problem, but won’t provide any information beyond that. On the other hand, digital integration sensors show the scientist which condition is out of parameter, allowing you to better understand the problem and make an educated assessment as to the amount of damage done.
There is also the option of 3rd party sensors and lab monitoring services, which provide the most in-depth data regarding conditions. In areas prone to power outages or for researchers working with a large amount of extremely sensitive cells—think an IVF facility—external monitoring services are an ideal solution. These systems provide the most peace of mind, as well as the most technology advanced features, such as Bluetooth compatibility and real-time notifications.
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