95% upper bounds on the fraction of galaxies, f ₉₅, as a function of the waste heat luminosity threshold L _wh,thr, for radiator temperatures T = {150, 200, 300, 400, 600} K. The analysis uses the STRICT sample (artifact–clean per band) with the combined Stern+Assef+Jarrett AGN/starburst masks applied. Upper limits are per object “flux caps” (W3/W4) with k = 3 (i.e., 3σ), and no stellar RJ subtraction unless otherwise noted. Curves are monotonic and converge where essentially all galaxies are sensitive; see Figure 4 for the corresponding denominators.