Well, simple may be relative. I've got a question that i'm looking for a simple equation for. Maybe someone can help me out... here it is; You have a pressure vessel with known volume that you want to keep at a known positive pressure (if it helps, assume that the atmosphere is at vacuum). If you have a known inlet flow of oxygen (in liters/min and is a set value, or non-variable), how can you find the maximum hole (leak) in the pressure vessel to stay at the desired pressure. Lets say that the pressure starts at what you want, and then you develop a hole or leak at the exact time the inlet flow begins, and friction/thermal effects are negligible. Thanks for your smarts!