In a pressurized system that contains a liquid or gas, when the pressure is too high the system can rupture at its weakest point, causing a halt to operations, damage to the system and, possibly, leakage of dangerous materials into the environment. To protect against this, people install relief valves. The valves guard against excessive pressure and wrong-way flow. One type of relief valve vents into the atmosphere. It is used in applications that do not have hazardous liquids or gases. Another type can direct dangerous fluids to an alternate route, possibly collecting them in a reservoir of some sort, while protecting the system from damage.