NOVELTY - An apparatus comprises an impurity generating source, pure gas supply, main gas conduit, communication between the impurity source and a portion of the main conduit, a housing, where the impurity source and the portion of the main conduit is located within an interior of the housing, a device for selectively raising and/or lowering the temperature of the housing interior at 60-130 degrees F and a temperature controller for controlling the temperature within the housing.    USE - For providing gases for calibration (claimed).    ADVANTAGE - The apparatus ensure a more accurate, precise and reliable calibration of gases or liquid analyzers, as the apparatus are capable of heating, cooling and maintaining the temperature of the environment where the apparatus are housed. The apparatus provide enhanced quality control and product end quality. The apparatus are well suited for devices that emit gases at constant rate, particularly to commercially available gas emitting devices that are used to produce calibration gases. Additionally due to controlled temperature and flow conditions, the apparatuses have a longer life. The apparatus can be used to accurately calibrate a gas chromatograph and a sulfur analyzer for carbon dioxide, which is especially critical for low concentration like ppm.    DETAILED DESCRIPTION - A gas calibration apparatus (I) comprises at least one source that generates at least one chosen impurity in a known range of nanograms per minute within given temperature ranges and at a predetermined flow rate, a substantially pure gas supply, a main gas conduit, communication between the impurity source and at least a portion of the main conduit, a housing having an interior, where the impurity source and the portion of the main conduit is located within the interior of the housing, a device for selectively raising and/or lowering the temperature of the housing interior at 60-130 degrees F, a temperature controller for controlling the temperature within the housing. The pure gas flows through the main conduit and passes by the communication. The impurity from the source diffuses into the pure gas that flows past the communication to produce the calibration gas.    INDEPENDENT CLAIMS are also included for:    (1) an apparatus (II) for producing calibration gases comprising a source that produces a chosen gas impurity in a known range of nanograms per minute within given temperature ranges and at a predetermined flow rate; a main gas conduit selected from sulfur inert tubing; a communication between the impurity source and the conduit; an insulated housing that holds the impurity source and at least a portion of the main conduit; a semi-conductor heating and cooling device for raising and/or lowering the temperature in the housing; a temperature controller that controls the temperature within the housing; a device to circulate heated or cooled air within the housing; a switch that controls the semi-conductor device and determines whether the device produces heat or cooling, where the temperature in the housing is maintained at 60-130 degrees F during standby or when calibration is desired. The purge gas flows through the conduit during standby and passes by the communication to cause the impurity source to diffuse into the purge gas when the apparatus is not being used to produce a calibration gas; a flow controller for maintaining the desired flow of gases within the conduit; where pure gas is introduced into the conduit when calibration is desired and where the impurity diffuses into and mixes with the pure gas that passes by the communication to provide a calibration gas; and where the calibration gas is conveyed through the conduit to an instrument;    (2) production of gases for calibration involving providing a source for generating a chosen impurity at a rate having a known value range of nanograms per minute within given temperature ranges and a predetermined flow rate, supplying at least one gas conduit, providing an insulated housing, placing the impurity source and at least a portion of the at least one gas conduit within the housing; controlling the temperature within the housing at 60-130 degrees F during standby or when calibration is desired, providing a communication between the conduit and impurity source and providing a supply of pure gas, making a calibration gas by and allowing the impurity source to diffuse into the pure gas that flows past the communication, thus mixing with the pure gas and using the calibration gas to calibrate an instrument; and    (3) a system for providing a more accurate calibration of instruments for testing gases, comprising the impurity generation source, the main gas conduit; the housing, the device for selectively raising and/or lowering the temperature of the housing interior at 60-130 degrees F, a flow controller that allows gas to flow through the main conduit at 0.5-2 liters/minute, communication between the impurity source and the main conduit, where pure gas flows through the main conduit and past the communication and where the impurity source diffuses into the pure gas and mixes with the pure gas to form a calibration gas, an instrument that is capable of being calibrated, a connection between the instrument and the main conduit, where the calibration gas is fed to the instrument that analyzes the gas. The instrument is calibrated based on the analysis and the known value of the source.