We have precisely measured stress distributions in the quartz tubes of high‐energy linear flash lamps, and determined the correlations between the measured stress and flash lamp explosion. Premature lamp explosion can be ascribed to the initial tensile stress at the outer surface of the tube, whereas normal lamp explosion can be ascribed to the accumulated tensile stress at the inner surface. The upper limits of the stresses in these two cases are given so that they can be used to prevent the lamp explosions by removing marginal tubes from use before explosion.