Incubators are used in biological experiments to allow growth of organisms in optimal conditions of temperature, carbon dioxide and humidity. Incubators are generally supplied in one of three configurations, air jacket, dry wall and water jacket. Air draft incubators are popular among larger-volume models designed to allow for quicker recovery times. Air draft (or forced draft) incubators circulate air throughout the interior of the incubator to maintain constant temperatures. Dry wall incubators have the advantage that they can better adapt to ambient changes and require less maintenance. Water-jacketed incubators advantages include stable temperature control and increased security in the event of power failure (due to water's natural insulation abilities).
Incubators are often times equipped with carbon dioxide sensors to measure carbon dioxide concentrations within the unit. Types used include infrared sensors and thermal conductivity sensors. For applications requiring several door openings, IR sensors will provide accurate CO2 readings without having to wait for humidity to stabilize. Incubators with IR sensors will generally cost slightly more than the same incubator with a TC sensor. Currently, many sensors are constructed of platinum, which some manufacturers claim stands up to corrosion quite well. Thermal conductivity sensors measures changes in temperature internally and have proven their effectiveness over time. These sensors, however, are sensitive to changes in humidity. Infrared CO2 sensors measure diffraction of CO2 internally and are purportedly impervious to relative humidity and less susceptible to drift over time because they have auto-zero calibration cycles every few hours.
There are several parameters that are important to consider in specifying incubators. These include chamber capacity, the volume of the chamber that is available for allowing growth; temperature range, the range of temperatures the incubator can control; temperature control accuracy, the closeness of an indication or reading of a measurement device to the actual value of the quantity being measured. Usually expressed as percent of full-scale output or reading; relative humidity, the range of humidity the incubator can control; carbon dioxide range, the range of atmosphere the incubator can produce; and carbon dioxide control, the degree of control of carbon dioxide the incubator can achieve.
Features common to incubators include built-in alarms, adjustable door heaters, stackability, and interior lighting.