The CO2 incubator is a must for certain types of cell culture including mammalian cell culture. Mammalian cells tend to thrive at a pH of about 7.4. However some cell lines need slightly more acidic (7.0) or basic (7.7) media than other cell cultures. The bicarbonate buffers such as HEPES used in the culture medium are affected by the CO2 in the atmosphere thereby changing the pH. An atmosphere of 4 to 10% CO2 depending on the pH required will help to maintain the proper balance of CO2 to bicarbonate. CO2 incubators can be air jacketed, or water jacketed if more precise temperature control is needed. Inside the incubator a sensor monitors the temperature, the microprocessor uses this information to control the temperature. If the incubator is used routinely at the same temperature a thermal conductivity (TC) sensor is sufficient. If the conditions in the incubator must be changed frequently an infrared (IR) sensor is a better choice. CO2 incubators can be as small as 1.4 cu.ft. and larger than 30 cu.ft. Some CO2 incubators also have controls for N2 and/or O2. The gases must be supplied by cylinders which are secured safely and using the proper regulator. Manufacturers of CO2 incubators include but are not limited to: Caron, Shellabs, Binder, Thermo Scientific, and VWR.