In this paper, authors apply a double sampling procedure for the improved np chart and pro- vided the designs that minimize the ARL1 against increases of 50%, 100% and 200% in the process non-conforming rate. This procedure was applied to processes with in-control non-conforming frac- tion p0 equal to 0.005, 0.010 and 0.020 and for ARL0 ≥ 200 and for ARL0 ≥ 370.4. The optimal designs were given for average sample sizes such that np0 = 0.5, 1.0, 2.0 and 4.0. In all these cases it was found that the double sampling minimizes the number of samples needed until the detection of one item out of control in the process.