First off by using your own figures and converting your one cubic foot of air. If you changed it to 1 PSI and compressed it 13.27 times what would your air pressure be now? It should be 13.27 PSI, but it won't. Now I'll admit my mistake. I forgot to add into the formula the heat generated by compression. Along with heat, comes an increase in the moleular activity of the subtance being heated. When a gas is heated the pressure increases, therefore you can have pressures higher than just the mathmatical formula states. I stand corrected.