Incuvers Blog

Things To Consider When You Choose Your Cell Incubators Vol. 1

Reading time: 4 minutes

Timber Shao - Marketing Specialist, Incuvers

Apr. 23, 2019

Biological CO2/hypoxic incubator Guide

Selecting the right incubator for your lab is critical. Wrong decisions can be very costly and more importantly may not meet your needs. Whether you are a biology newbie or a cellular research guru, in this post, we will break down each type of incubator along with a side-by-side comparison.

Heating Methods Explained:

Air-Jacketed Heating.

Air-jacketed incubators keep the incubator warm by heating up the external air supply delivered to the inner chamber. The working principle of air-jacketed incubators requires a gas supply and a microprocessor. This constantly regulates the temperature of the air input based on feedback from the temperature sensor.

  • Combined with proper insulation, Air-jacketed incubators provide robust temperature uniformity and stability.
  • Air-jacketed incubators rapidly warm up inner chamber temperature fluctuations without overheating the chamber wall.
  • Due to the fact that air-jacketed incubators constantly input warm air; humidity within the chamber is much harder to stabilize.
  • Ideal chamber for performing in-vitro heat shock activation


Water-jacketed incubators maintain temperatures using water-filled containers that wrap around the chamber surface. By circulating and heating water, the temperature within the inner chamber can be gently and uniformly regulated.

  • Water (or solutions with an ideal heat capacity) acts as a thermal buffer between the heat source and the inner chamber atmosphere, providing a maximum thermal stability.
  • Heat retention: Water-jacketed incubators come especially handy during power failures as water retains heat more efficiently. This results in faster heat recovery and heat retention.


Direct Heat Incubators are self-explanatory. Instead of having a water jacket, direct heat incubators are usually equipped with a layer of hard-board insulation between the inner chamber and the heat coil.

  • Direct heat incubators provide much faster heat modulation which is especially useful when studying cellular and biomolecular responses that require acute temperature changes.
  • Some direct-heat incubators are capable of raising temperatures to very high points to achieve sterilization/decontamination effects. However, frequent high-temperature sterilization can have a detrimental effect on temperature sensors.
CO2 Incubator Heating

💡 Tip: Proper sealing of incubator doors also plays a part in temperature uniformity and stability. Besides rubber magnet seals as a common practice, double-door design, secure lock, and gas-tight doors can all be additional measures.

💡 Tip: Placing other equipment in the incubator can potentially affect temperature uniformity and regulation. Most incubators are not designed for hosting anything other than cell culture containers. Overheating issues in incubators have been increasingly reported based on misuse.

Air Flow Explained:

Gravity Airflow.

Gravity is one way to control airflow within an incubator: Cool air condenses and falls while warm air rises within the chamber.

  • One of the biggest plus points of Gravity convection incubators is they are budget-friendly due to the lack of fans, however, this is also a limitation.
  • Because there is no active air flow, gravity convection incubators tend to have poor performances in keeping the temperature uniform.
  • A lower chance of cross-contamination between samples compared to its counterpart.

Forced Airflow.

To precisely control the CO2 concentration within the chamber, an external air (mainly CO2)  input is required. This led to the development of a forced-air incubator.

  • As mentioned in the earlier section, a constant input of air can negatively impact the humidity control in the incubator.
  • Certain incubators can overcome drying effects by coordinating air flow rates and temperature acceleration. Forced-air flow leverages seamless integration with temperature sensors, humidity sensors, heaters and fans.
  • Without graded filtration systems (e.g. HEPA filter), there is a higher chance of cross-contamination of samples.
CO2 Incubator Airflow

💡 Tip: HEPA filters are usually classified based on its Retention rate at the given most penetrating particle size. It is a common practice for biological incubators equipped with the HEPA filtration system to establish an ISO-5 cleanroom air quality. While some retailers offer HEPA filter kits in addition to the incubator, some incubators can come with a HEPA filter pre-installed.

Air Supply Explained:


In order to mimic in-vivo conditions, the CO2 tension within the chamber must be different from the atmosphere. In addition, Different cell lines require different optimum [CO2]. A previously regulated [CO2] is essential to sustain the PH of cell culture.
Two types of CO2 sensors:

  • Infrared (IR) CO2 sensor: IR CO2 sensors offer precise and sensitive monitoring of [CO2] with a deviation of approximately 0.1%.  They are ideal for applications that require sensitive controls and responses in [CO2].
  • Thermal Conductivity (TC) CO2 sensor: TC CO2 sensors offer more robust and reliable operation with minimum maintenance. TC sensors work mathematically by measuring the thermal conductivity changes when the CO2 is introduced. Thus, its sensitivity can be affected by changes in temperature and humidity.


Physiological in-vivo oxygen tension can range from 1% to 13%, while atmospheric oxygen tension fluctuates around 21%; thus, there is no doubt that specifically regulated [O2] is critical for optimizing incubation conditions. Dynamically modulating [O2] in incubators optimizes the incubation environment as well as imitates physiological stimuli on the cellular level. As an example, in-vitro ischemic events and hypoxia-induced autophagy.

  • Hypoxia: A hypoxia condition (with [O2] < 5%) can be adequately achieved in multi-gas incubators with external N2 supply, which can drastically suppress the ambient [O2].
  • Normoxia: Normoxia refers to oxygen tension between 10–21%. Multi-gas incubators can simulate/recover into Normoxia by pumping large amounts of natural air supply in a short time.
  • Hyperxia: Oxygen tension above 21% is usually referred as Hyperxia. Multi-gas incubator can simply achieve hyperxia by pumping in external O2 supply (if the incubator is equipped with a O2 access port).

What's More?

Heating, Air Flow, and Air Supply construct the foundation of biological incubators. However, that is not enough to maintain a healthy cell culture. Factors like Contamination and Relative Humidity are relatively difficult to predict and regulate. Therefore, live cell culturing always requires a massive amount of manual input and financial cost.

In the upcoming volume, we will be talking about more attributes of contemporary incubators : Dimension, Water Reservoir, and unusually, Imaging systems.

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Tri-gas incubator with live cell imaging

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