This article reports on a general method of evaluating exposure to infrared radiation (IR-A, IR-B, IR-C) from high temperature (T > 1000 degrees C) black body sources, simply by performing measurements with a luxometric and/or near IR detector. The method, which may be applied to any black body source, uses the universality of the Planck formula for the black body spectrum, which allows estimation of the radiated power in any wavelength range by measuring the power radiated in another range. This capability may be very useful when the range of interest is one in which radiometers are expensive and difficult to calibrate, as for the IR-B and IR-C ranges, because a more commonly available luxometer can be used instead. The results of measurements and evaluations in two traditional Italian glass factories are reported and compared with the threshold limit value given by the American Conference of Governmental Industrial Hygienists. Intense exposures in the IR-B and IR-C ranges has been found for some workers, exceeding the limit by a large factor. This exposure must be reduced, as it has been shown by epidemiologic studies that there is indeed a correlation between cataractogenesis and work with fused glass and metals.