Abstract
In a recent letter, Yaldram et al.(1993) studied the critical behaviour of a simple lattice gas model of the CO-NO catalytic reaction. The model exhibits a second-order non-equilibrium phase transition from an active state into one out of infinitely many absorbing states. Estimates for the critical exponent beta suggested that the model belongs to a new universality class. The results reported in this article contradict this notion, as estimates for various critical exponents show that the model belongs to the universality class of directed percolation.