  The properties of the fluctuations large enough to induce bifurcations at
open chemical systems at steady constraints are studied. The fluctuations that
come from the diffusion-induced noise are considered. It is a generic for the
surface reactions driving mechanism of fluctuations whose distinctive property
is that it generates bounded fluctuations at any value of the control
parameters. The range of boundedness is specific to a system but it is such
that the system permanently stays within its thresholds of stability. This in
turn ensures long-term stable evolution of the system. The frequency for
occurrence of an induced bifurcation is carried out analytically. Its important
property is that it gradually becomes insensitive to the reaction mechanism on
increasing the excursion size.
