than 440 °C. Current safety measures regarding the usage of hydrocarbons are outlined by the Environmental Protection Agency (EPA). EPA guidelines of hydrocarbon usage as a refrigerant include specifically designating pressure ranges for hydrocarbon refrigerant systems, ensuring the removal of potentially fire-starting components from hydrocarbon refrigerant systems such as electrical components prone to sparking, and placing standards on the construction of the systems to ensure a higher level of safety. Installing ventilation such that the concentration in air would be less than the flammability limit and reducing the maximum charge size of the refrigerant are other viable safety measures. Technological advances to reduce the total refrigerant charge amount have been recently obtained using aluminum mini-channel heat exchangers. Applications and uses Hydrocarbon refrigerant markets have been growing as a result of increased concern for environmental effects of typical synthetic refrigerants. According to ASHRAE, available equipment that utilizes hydrocarbon refrigerant includes the following: Systems with small charges such as domestic refrigerators, freezers, and portable air conditioners Stand-alone commercial refrigeration systems including beverage and ice-cream machines Centralized indirect systems for supermarket refrigeration Transport refrigeration systems for trucks Chillers in the range of 1 kW – 150 kW Carbon dioxide as a refrigerant (R-744) Carbon dioxide has seen extensive use as a refrigerant. Carbon dioxide's main advantage as a refrigerant stems from the fact that it is classified as an A1 refrigerant by the EPA, placing it in the least toxic and hazardous category for refrigerants. This makes carbon dioxide a viable refrigerant for systems that are used in areas where a leak could cause exposure. Carbon dioxide sees extensive use in large-scale refrigeration systems, sometimes via a cascade refrigeration system. It is also used sparingly in automotive refrigeration, and is seen as favorable for uses in domestic, commercial and industrial refrigeration and air conditioning systems. Carbon dioxide is also both plentiful and inexpensive. These factors have led to carbon dioxide being used as a refrigerant since 1850, when it was patented for use as a refrigerant in the United Kingdom. Carbon dioxide usage at the time was limited due to the high pressures required for refrigerant properties to manifest, but these pressures can be easily reached and sustained with current pressurization technology. The main concern over the use of carbon dioxide in refrigeration is the increased pressure required for carbon dioxide to act as a refrigerant. Carbon dioxide requires higher pressures to be