A chemochromic sensor for detecting a combustible gas, such as hydrogen, includes a chemochromic pigment and a textile polymer. The computer code instructions are encrypted using a chaining mode so that an encrypted instruction depends on the values of the instruction, the value of the preceding instruction and a pseudo-random number. The predictor equation is determined by a linear regression technique that includes a correlation analysis of the virtual instructions, removal of highly correlated instructions, and a combination of stepwise linear regression and multiple linear regression to determine the predictor equation.