  In this paper, we investigate absorbing sets, responsible of error floors in
Low Density Parity Check codes. We look for a concise, quantitative way to rate
the absorbing sets' dangerousness. Based on a simplified model for iterative
decoding evolution, we show that absorbing sets exhibit a threshold behavior.
An absorbing set with at least one channel log-likelihood-ratio below the
threshold can stop the convergence towards the right codeword. Otherwise
convergence is guaranteed. We show that absorbing sets with negative thresholds
can be deactivated simply using proper saturation levels. We propose an
efficient algorithm to compute thresholds.
