Validation

In microbiology an incubator is a device for controlling temperature, humidity, and other conditions under which a microbiological culture is being grown. The simplest incubators are insulated boxes with an adjustable heater, typically going up to approx. 65 °C. Some incubators can go slightly higher but generally to no more than 100 °C. More advanced incubators may have the ability to lower the temperature (via refrigeration), and/or the ability to control humidity or CO2 levels. This feature is specifically designed for cell growth.

Most incubators provide inner and outer glass doors for transparency. The main controller includes a timer. Some can also be programmed to cycle through different temperatures, humidity levels, etc. Incubators can vary in size from table tops units to units the size of small rooms. Incubators may also provide special features such as regulation of shake speed.

As for temperature, 37°C is a commonly used temperature in incubators being the normal human body temperature. Most bacteria, especially the frequently used E. Coli, grows well under such conditions. For other applications lower temperatures are required, (for fish cells a growth temperature of 25°C is optimal).

Guidelines

The Current Good Manufacturing Practice for manufacturing, processing, packing or holding of drugs and Current Good Manufacturing Practice for finished pharmaceuticals is described in 21 CFR Parts 210 and 211. Subpart D describes handling of equipment (that it shall be routinely calibrated, inspected or checked according to a written program designed to assure proper performance). Furthermore, DIN 12880-2 specifies performance requirements and tests for heating cabinets and incubators in laboratories. The standard applies for cabinets and incubators with a working temperature range from -10°C to 300°C and includes shaking incubators.

Validation of an incubator consists of various steps regarding Installation Qualification (IQ), Operational Qualifications (OQ) and Performance Qualifications (PQ).

The IQ is conducted to demonstrate that the incubator is inspected and contains all the required parts to ensure functionality.

In the OQ, the performance of the incubator and its operational procedure is verified. The OQ consists of temperature mapping of the empty chamber and is performed to confirm that the empty chamber works within the specified limits throughout the chamber. The OQ also contains information about the calibration of measuring equipment and defines the location of the thermocouples and /or data loggers in the incubator.

Measuring Points

The typical number of measuring points is 5 (4 corners + center) on the lower and top shelf. During OQ these are fixed directly on the shelves in an empty chamber and during PQ they are placed into loaded samples. For larger chambers it is recommended to place 5 measuring points on a minimum of 3 layers or on each layer with sample readings every 1- 5 minutes for 24, 48 or 72 hours.

Ellab’s wireless loggers are ideal for such qualifications. Even most standard incubators provide access port(s) the cable feed through could disturb the integrity of the chamber atmosphere. For example, the acceptance criteria for a standard incubator with a set point of +37°C, is that all measurements throughout the chamber do not individually differ by more than 2°C and all measurements maintain temperature around 32°C to 37°C.

With biological incubators the temperature validation is similar to above whereas the number of relative humidity measuring points is dependent on the chamber design (the ability to circulate air typically performed by a fan). Often a minimum of 2-3 RH sensors are placed throughout the chamber and the same is valid for CO2 measurement.