We sell a lot of refurbished incubators, and a large portion of those are CO2 incubators used for cell or tissue culture. Some customers prefer water-jacketed models while other people prefer air-jacketed units (also known as direct heat units). Today we’ll look at the differences between the two types along with some of the advantages and drawbacks of each design.
Water jacketed CO2 incubators
As the name implies these units utilize a water container or “jacket” that surrounds the chamber on five sides to help maintain temperature stability despite door openings or fluctuating ambient conditions. Because water has a high heat capacity and holds temperature longer than air, the incubator jacket will help the chamber maintain a steady, consistent temperature level and recover heat loss quickly if the door to the incubator is opened or in the event of a power outage.
The potential downside to this stability is that reaching setpoint temperature with a water jacketed incubator can take up to 24 hours. This is not the end of the world for most labs, but if you plan to use the incubator for different applications that require different temperature settings the temperature stabilization time should at least be taken into consideration.
The biggest drawback to water jacketed incubators in our opinion is the risk of contamination. Think about it: you’re talking about a warm, dark, wet environment, perfect for bacterial and fungal growth. Even if you use distilled, sterile water to fill the chamber the threat of contamination exists. If contaminated the jacket must be cleaned before you can continue using the incubator.
Water-jacketed units are also heavy. To fill a typical Thermo model, for example, requires 11.7 gallons of water. At 8.34 lbs per gallon, that means the water alone weighs almost 100 lbs, and so a stacked pair of these incubators can weight upwards of 700 lbs.
Air jacketed CO2 incubators
Air jacketed or direct heat CO2 incubators are easier to set up and get into quick operation than water jacketed models because they don’t have to filled with distilled water and they can reach setpoint temperature more quickly. These units produce chamber heat by conduction via heating elements on the exterior of the chamber walls. Temperature uniformity in the chamber of air jacketed models has improved significantly in the last 10 to 15 years but in general they still don’t have the same uniformity or stability as water jacketed units. The air jacketed design also allows for high heat sterilization/decontamination cycles of temperatures up to 180°C.
The big drawback to direct heat models is less the issue of stability and more the issue of longer temperature recovery time after door openings than their water jacketed counterparts. Additionally, should a power failure in the lab occur these models can lose temperature up to five times faster than water jacketed models.
Summary
At the end of the day, most times the decision comes down to personal preference, previous experience, and budget. We still stock the classic Forma 3110 water jacketed CO2 incubator, which was an industry standard for decades, as well as newer vintages like the Thermo Forma 4110. On the other hand, many of our customers prefer air jacketed models like the Binder C150 and Panasonic MCO series because of the sterilization cycle option. As always, feel free to call or email us with any questions about incubators or other lab equipment.
American Instrument Exchange has been a reliable source for used laboratory and scientific equipment for over 50 years, buying and selling equipment since 1969. Our surplus lab equipment is reconditioned for many types of laboratories, including biotech, biomedical, medical research, chemical, pharmaceutical, and university and hospital research laboratories. All lab equipment listed on our website is in stock and ships from our 30,000 square foot warehouse in Massachusetts. Our facilities include a fully equipped shop with highly trained technicians who thoroughly test each instrument before it reaches your laboratory. Please visit our website at https://www.americaninstrument.com/.