A kind of red LEDs with a wavelength of 655nm provides light illumination of loess samples while pretreating the samples with minimal effect on the latent IRSL. The IRSL signal is decreased to two percent after 20 minutes bleaching by sun light. It implies that the residual signals may be neglected even when dating very young loess samples

and that IRSL dating has significant potential in dating very poorly-bleached sediments. The recuperation of IRSL in loess is negligible

so the measurable age limit for IRSL is much lower than that for GLSL.