Ambient temperature is a term to denote a certain temperature within enclosed space at which humans are accustome Room temperature is thus often indicated by general human comfort, with the common range of 18°C to 28°C, though climate may acclimatize people to higher or lower temperatures.
As used in the petroleum marketing industry, however, ambient temperature means the outside temperature of the surrounding area at a particular location.
The term can also refer to a temperature of food to be consumed, which is placed in such a room for a given time. Furthermore, it may refer to a certain temperature within settings of scientific experiments and calculations.
The progress and results of many scientific and industrial processes depends a little or not at all on the temperature of the surroundings of the equipment. For example, a measurement of the charge of the electron does not depend upon the temperature of the test equipment. In such cases if any mention of temperature is made, it is customary and sufficient to speak simply of "room temperature", which implies that no specific cooling or heating was involved. In most cases considerable temperature variations are irrelevant; work may be carried out in winter or summer without heating or air-conditioning, without mention of the temperature.
The phenomena that researchers may choose to study at room temperature can naturally occur in the range of 20 to 23.5 °C, or they may not. Researchers will choose to study a process outside its natural temperature range when they expect the conclusions to a specific question to be the same at room temperature as at a more natural temperature.
Experimentalists have an advantage in anticipating aspects of a room-temperature experiment, because the temperature is close to 20 °C, at which many of the material properties and physical constants in standards tables have been measured (more at standard state). By consulting such tables a researcher may estimate, for example, how fast a chemical reaction is likely to proceed at room temperature.
Unless there is a reason to work at a specific temperature, it is clearly more convenient not to control the temperature. Even in cases where a known, controlled, temperature is advantageous but not essential, work may be carried out at room temperature. But, for example, very large, warehouse-type experimental facilities may lack sufficient heating and cooling capabilities to maintain 'room temperatures'.
If it is believed that work which may have some dependence upon temperature has been carried out at temperatures significantly outside the range 20 to 23.5 °C, it may be reported that it was carried out at an ambient temperature of some approximate specified value.
An assumed typical ambient temperature may be used for general calculations; for example, the thermal efficiency of a typical internal combustion engine may be given as approximately 25 percent, with no mention of the air temperature: the actual efficiency will depend to some extent on ambient temperature, decreasing in extremely hot weather conditions due to lower air density.