inexpensive. It has a GWP and ODP of zero, making ammonia leaks negligible on the climate. Ammonia is also tolerant to mineral oils and low sensitivity to small amounts of water in the system. The vaporization heat of ammonia is high and the flow rate low, which requires different technologies to be used than other refrigerants. The low flow rate has historically limited ammonia to larger capacity systems. One of the largest issues with ammonia usage in refrigeration is its toxicity. Ammonia is lethal in certain doses, but proper preparation and emergency protocols can mitigate these risks down to as little as one death per decade, according to the EPA. The unusual smell of ammonia is one reason for that, which allows humans to detect leaks at as low as 5ppm, while its toxic effects begin above 300ppm. Exposure of up to thirty minutes can also be handled without lasting health effects. As a result, much of the hazard with using ammonia as a refrigerant is actually just a matter of public perception. The main focus of safety measures is therefore to avoid fast increases in concentration to a public panic level. Flammability is also not of particular concern, since the flammability range is 15-28%, which would be detected far in advance. It is classified as 2L by ASHRAE for low flammability. Applications and uses Ammonia based refrigerant applications can include the following: Thermal storage systems HVAC chillers Process cooling Air conditioning Winter sports District cooling systems Heat pump systems Supermarkets Convenience stores Increasing output efficiencies for power generation facilities Ammonia is expected to see increased use in HVAC&R industries as more officials become informed of its relative safety. It is already used in large heat pump installations and grocery stores, as well as in projects such as the International Space Station. Similar to carbon dioxide, ammonia can also be used in cascade refrigeration systems in order to improve the efficiency of the refrigeration process. There is an increasing use of cascade refrigeration systems that contain both ammonia and carbon dioxide. Absorption chillers with a water/ammonia mixture are also cost effective in some applications such as combined chilling, heat and power systems. Advancing technology also makes ammonia an increasingly viable option for small-scale systems. Water as a refrigerant (R-718) Water is nontoxic, nonflammable, has a zero GWP and ODP value, and has a low cost. Technical challenges, such as water's