Critical Point
The critical point (critical temperature and critical pressure) means the substance has gone above the point when there is no longer a boundary between liquid and gas.
A substance above its critical point is always in the gaseous state.
At temperatures below the critical point, all types of refrigerant in pressure reservoirs exhibit both a liquid and a gas phase meaning there is a layer of gas above the liquid.
As long as there is still gas present in the container next to the fluid, pressure is dependent on ambient temperature. Refer to REFRIGERANT VAPOR PRESSURE TABLE .
The refrigerants used in vehicles must not be mixed. Only the refrigerant designated for the corresponding A/C system may be used.
The vapor pressure of both refrigerant R1234yf and R134a are very similar across a large temperature range for this reason no differentiation of the two refrigerants is possible. Refer to REFRIGERANT VAPOR PRESSURE TABLE and A/C System, General Information . Distinguishing is only possible by suitable sensors which can analyze the chemical characteristics of the refrigerant. Refer to REFRIGERANT R1234YF ANALYSIS .