Exposure to IR-A and IR-B radiation, in the wavelength region of 780 nm to 3,000 nm, may lead to the development of cataractogenesis. Estimation of the exposure levels is the first step in controlling adverse health effects. In the present study, the irradiance of a hot blackbody emitter is replaced by its temperature in the exposure limit values for cornea and lens in the range of 780-3,000 nm. This paper explains the development and implementation of a computer code to predict a temperature, defined as Threshold Temperature, which satisfies the exposure limits already proposed by the ICNIRP. To this end, first an infinite series was created for the calculation of spectral radiance by integration with Planck’s law. For calculation of irradiance, the initial terms of this infinite series were selected, and integration was performed in the wavelength region of 780 nm to 3,000 nm. Finally, using a computer code, an unknown source temperature that can emit the same irradiance was found. Exposure duration, source area, and observer distance from the hot source were entered as input data in this proposed code. Consequently, it is possible only by measurement of a Planckian emitter temperature and taking into account the distance from source and exposure time for an observer to decide whether the exposure to IR radiation in the range of 780 to 3,000 nm is permissible or not. It seems that the substitution of irradiance by the source temperature is an easier and more convenient way for hygienists to evaluate IR exposures.