  In a recent letter [J. Phys. A26, L801 (1993)], Yaldram et al. studied the
critical behaviour of a simple lattice gas model of the CO-NO catalytic
reaction. The model exhibits a second order nonequilibrium 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.
