A continuum structure function(CSF) is a non-decreasing mapping from the unit hypercube to the unit interval. The reliability importance of component $i$ in a CSF at system level ${alpha}$, $R_i({alpha})$) say, is zero if and only if component $i$ is almost irrelevant to the system at level ${alpha}$. A condition to check whether a component is almost irrelevant to the system is presented. It is shown that $R^{(m)}_i({alpha}){ ightarrow}R_i({alpha})$ uniformly as $m{ ightarrow}{infty}$ where each $R^{(m)}_i({alpha})$ is readily calculated.