pump. Onboard compressors are cheaper and easier than having a dedicated pumping house. The air is generally cooled and excess moisture is removed before it is sent out of the plant. Some systems even cool the water before it enters the system. This improves the snowmaking process as the less heat in the air and water, the less heat must be dissipated to the atmosphere to freeze the water. From this plant the air travels up a separate pipeline following the same path as the water pipeline. Ice nucleation-active proteins The water is sometimes mixed with ina (ice nucleation-active) proteins from the bacterium Pseudomonas syringae. These proteins serve as effective nuclei to initiate the formation of ice crystals at relatively high temperatures, so that the droplets will turn into ice before falling to the ground. The bacterium itself uses these ina proteins in order to injure plants. Infrastructure The pipes following the trails are equipped with shelters containing hydrants, electrical power and, optionally, communication lines mounted. Whereas shelters for fan guns require only water, power and maybe communication, lance shelters usually need air hydrants as well. Hybrid shelters allow maximum flexibility to connect each snow machine type as they have all supplies available. The typical distance for lance shelters is , for fan guns . From these hydrants pressure resistant hoses are connected similar to fire hoses with camlocks to the snow machine. The infrastructure to support snowmaking may have a negative environmental impact, altering water tables near reservoirs and mineral and nutrient content of the soil under the snow itself. Snowmaking guns There are many forms of snowmaking guns; however, they all share the basic principle of combining air and water to form snow. For most guns the type or "quality" of snow can be changed by regulating the amount of water in the mixture. For others, the water and air are simply on or off and the snow quality is determined by the air temperature and humidity. In general there are three types of snowmaking guns: internal mixing, external mixing and fan guns. These come in two main styles of makers: air water guns and fan guns. An air water gun can be mounted on a tower or on a stand on the ground. It uses higher pressure water and air, while a fan gun uses a powerful axial fan to propel the water jet to a great