Why a crankcase relief door is not fitted in the refrigeration compressor crankcase?

a. Possibility of the contamination of the refrigeration system by air by leaks 
b. Oxygen is not available in the compressor crankcase 
c. The incoming refrigerant temperature is low and chances of hot spots is low 
d. Crankcase forms the suction chamber of the compressor and chances exist that the 
compressor may draw in air and moisture