Some plants may be charged at the time of installation with a refrigerant which contains a coloured dye to provide a visual indication of leakage. Systems using refrigerant containing a dye must always be liquid charged. This is most important when adding refrigerant to a system after a considerable loss due to leakage.
The dye tends to separate from the refrigerant in the cylinder and is heavier than the liquid refrigerant. Therefore it is advisable to agitate the liquid when charging or adding refrigerant by placing the cylinder in a horizontal position and rocking it gently.