• It should be environmentally friendly.
  • The latent heat of evaporation should be high.
  • The critical temperature and pressure must be high.
  • The boiling point should be low at atmospheric pressure.
  • Saturation pressure should be below the pressure of the regulator valve.
  • Air leakage, that is, the water vapor brought by the air should solidify in the cold parts to prevent operational disruptions, and for this, the evaporation pressure should be slightly above the ambient pressure.
  • It should not damage the tools used in the construction of the holding oil and other components that make up the installation.
  • There should be no corrosion effect.
  • It should not transform into a chemical change in any part of the system.
  • It should not be flammable, explosive and toxic.
  • It should be easily available and cheap.
  • It should be suitable for the use of a small capacity compressor.
  • Closed circuit should be able to detect leaks easily.
  • For high cooling capacities, the latent heat of evaporation should be large so that the compressor sizes are not too large.