In a recent Lab Manager webinar, we discussed in depth which types of CO2 incubator humidity control technologies to look for to provide optimal relative humidity and condensation control for cell culture work. If you didn’t get a chance to attend this webinar, you can always view it on-demand here.
We received some great questions from attendees during the live webinar, and below is a summary for the benefit of all who need to control humidity and condensation for their work.
ignificant exposure to condensate can cause the accuracy of capacitive RH sensors (the type used in most CO2 incubators) to drift, and can lead to their failure, adding to increased maintenance costs, downtime, and the total cost of ownership of the incubator. This is why it is important to ensure that your incubator’s control algorithm factors in all relevant variables to control humidity. For a review of these factors, read our RH and condensation control paper.
While it is possible to attain good recovery times with a water pan, ultrasonic humidification offers the fastest recovery. As an example, Baker’s Cultivo® Ultra and Ultra Plus model CO2 incubators, which use a nebulizer to deliver humidity, recover humidity to set point in just 8 minutes after a 30-second door opening. The base model of Cultivo, which uses a water pan, recovers humidity to set point in just 10 minutes following a 30-second door opening. This is possible in part because of the water pan’s large surface area. Most incubators that use smaller water pans will not recover that quickly.
This is not necessary if you use a copper water pan. See our contamination control technology paper for more details on how to control contamination in your CO2 incubator.
Oxygen tension (the partial pressure of O2 dissolved within a liquid, such as blood plasma) can be controlled by managing the oxygen concentration (% O2) within the atmosphere of the incubated environment. A number of multi-gas incubators and controlled-oxygen workstations use gas mixing systems to control atmospheric O2 levels – anywhere from 0.0% (anoxia) to 21% (ambient) O2, with varying ranges and stability.
No, the CO2 level in the chamber operates independently of the water level in the pan.
If your CO2 incubator does not have an embedded RH sensor, there are stand-alone RH sensors available that can be placed inside the chamber to monitor RH. However, an important advantage to using an incubator with an embedded RH sensor is that the data that is collected feeds immediately and automatically back to the control algorithm, which is programmed to make adjustments as needed to keep conditions inside the chamber stable. This is simply not possible with a stand-alone RH sensor.
Calibration procedures differ by brand. You can request a copy of the calibration procedure for your specific CO2 incubator from the manufacturer.
As we discussed in the webinar, temperature does affect the accuracy of capacitive RH sensors. As temperature varies, RH sensor accuracy fluctuates from +/-1.8% to as high as +/-3.8%, with the least accurate RH detection occurring at the most common temperature condition, 37°C. This is why it is important that the incubator’s control algorithm accounts for a fluctuating RH sensor accuracy when controlling RH.
The RH sensor used in Cultivo has been pre-qualified to function correctly in normal atmospheric conditions, as well as with high concentrations of CO2 (up to 20%). Baker does not recommend operating Cultivo outside those conditions, and the presence of other gases may affect the RH sensor’s lifespan and accuracy. Check with your incubator manufacturer to learn more about the particular RH sensor used in your system.
The most common contamination control technologies in CO2 incubators are UV lights, copper interior components, and HEPA filters. A UV light is useful for controlling contamination in a water pan or reservoir, but there is a limit to its effectiveness. First, the effectiveness of a UV light is only as good as the intensity of the light’s wavelength. This intensity diminishes over time, and because the bulb continues to operate long after its germicidal effectiveness has weakened, it is not always obvious when it is time to change the bulb. Second, only contaminants that come into contact with the UV light waves will be killed. Many UV lights make use of a hood or other partial container, which prevents the light waves from reaching most of the interior of the incubator.
Copper has intrinsic properties that can assist in destroying a wide range of microorganisms. As such, copper is well known for its ability to control contamination in CO2 incubators. Purchasing a unit with a copper interior or copper interior components may further mitigate the risk of contamination, should you experience excessive condensation. Some incubator suppliers use copper infused materials in construction and design (where a percentage of the material is copper), while others provide an interior that is 100% copper. The use of copper within an incubator is the subject of continuing study by academic research laboratories around the world. It is unclear whether either copper-infused or 100% copper is more or less effective. It is certaintly contingent upon the microorganism and its resistance to the antimicrobial properties of copper. Should you wish to pursue copper as a method of contamination control, the limitation of this technology is fairly obvious: any surfaces that are not manufactured from copper are available to harbor contaminants. This includes plates, sensors, instrumentation placed inside the incubator, and any other interior component that is not made of copper.
While a HEPA filter does help to control contamination, it doesn’t help in the case of condensation, because it only captures contaminants in the air stream. However, we still recommend the use of a HEPA filter inside a CO2 incubator, preferably one with a large surface area for the most efficient filtration. Based on testing in our laboratory, the combination of a HEPA filter, UV light and copper interior components is the most effective at preventing contamination throughout the incubator.
In short, yes. The scientific method relies on systematic observation, measuring, and experimenting, as well as the formulation, testing, and modification of hypotheses. The tools, equipment, and instrumentation used to perform any test of a hypothesis are crucial links in that system, regardless of the level of education or complexity of research being performed. A hypothesis should be supported by results that are repeatable. As such, understanding or controlling the limitations of your current equipment, relative to the conditions your hypothesis requires, is crucial to the integrity of that experiment. Many tissues, cells, and microorganisms require precise environmental conditions to thrive. An incubator featuring control of temperature, CO2, and relative humidity can provide a learning tool to help students better understand the impact of one variable over a another on those cultures, affording them the opportunity to explore a wide array of research questions. In fact, relative humidity within an incubator chamber can impact these sensitive cell culture organisms, affecting their morphological and elastic properties, leading to a change in the structure of a cell wall and, therefore, growth rates.
A CO2 incubator is a vital component of many bioproduction processes. Some incubators provide innovative features within the control software and user interface that are integral to the system, which do help certain customers achieve compliance with Good Manufacturing Practices (GMP). Such incubators are specifically designed to help users meet requirements for data logging, electronic recordkeeping, security, and permissions. Some incubators identify, track, and record any changes made to the operational parameters, as well as log any errors or events critical to the operation of the system. When integrated into quality and validation protocols for each organization, these features can help the end user validate the performance specification of the equipment itself, relative to the desired outcome of the research or work being performed. It is important to note, however, that it is the end user’s responsibility for achieving compliance with all applicable regulatory guidelines, including GMP and FDA 21 CFR Part 11 compliance. Your incubator’s operator’s manual or your incubator supplier can provide you with more information on how your incubator may help you achieve compliance with these guidelines.
For a more in-depth overview of the latest RH and condensation control technology, download our paper, “Controlling Relative Humidity and Condensation in a CO2 Incubator”.