9000 Pascals Looking on the internet, it appears that a human can only suck about 3 feet of water. So let's convert that measurement into a few more convenient units. cmH2O = 36 * 2.54 = 91.44 cmH2O cmHg = 91.44 * 0.73555912101486 = 67.26 mmHg Pascal = 91.44 * 98.0665 = 8967 Pascals PSI = 91.44 * 0.0142233 = 1.3 psi Since we're dealing with science and the metric system is the most common system used in science, I'd recommend an answer of 9000 Pascals.