Abstract. We study and describe the quenching phenomenon for the fully nonlinear parabolic equation ut + 1 2 (ux) 2 = f (c u uxx) + ln u, x ∈ (0, l), t > 0, which for f (s) = ln[(e s − 1)/s] represents the evolution of the perturbations of the Zel'dovich-von Neuman-Doering square wave occurring during a detonation in a duct. In the general case, the function f : R → R is smooth and satisfies the parabolicity condition f ′ (s) > 0 in R, c and l are positive constants, and we impose Neumann boundary conditions ux(0, t) = ux(l, t) = 0 for t > 0 and take initial data u(x, 0) > 0 with inverse bell-shaped form.The phenomenon of quenching is characterized by the existence of a finite time T at which the solution u ceases to exist as a classical solution because minxu(x, t) → 0 as t → T ; then the equation degenerates and forms a singularity at the level u = 0, due to the presence of the logarithmic zero-order term.We first exhibit conditions on f and u(x, 0) which imply the presence of this type of singularity. Next we derive estimates on u , uxx in order to study the behavior of the profile in the neighborhood of the time T . We then find the asymptotic scaling factors, which are universal, and the asymptotic profile which is given in the rescaled coordinates by a parabola with a free constant to adjust. For this purpose we use the theory of stability of ω-limit sets of infinite-dimensional dynamical systems under asymptotically small perturbations. In this problem the perturbation is singular but exponentially vanishing as t → T . Finally, we prove that the present model does not admit any extension beyond the singularity, i.e., for t > T .