In an indirect refrigeration system there are two popular secondary coolants. Brine or Calcium Chloride and a Glycol solution. Brine has a better heat transfer coefficient, which makes it the more energy efficient option. This allows for smaller chiller applications that use less horsepower. Brine can be highly corrosive if not maintained correctly. All machinery that comes in contact with the brine solution must be stainless steel. It is also important to utilize a high grade rust inhibitor along with pH testing to monitor the brine solution strength. Glycol solutions are a lower maintenance option. It is still important to use high quality inhibited glycol and to test the solution once a year. Glycol solution is less corrosive, allowing for the use of carbon steel or cuper-nickle components. A glycol solution is the best option for portable systems that are occasionally exposed to the air while being drained or filled. Glycol systems are not environmentally friendly and the additives (corrosion inhibitors) can be hazardous.