Low temperature and medium temperature refrigeration systems used in trucks typically use __________ refrigerant.

Low temperature and medium temperature refrigeration systems commonly found in trucks often utilize R-404A as their refrigerant. This is due to R-404A's effective performance in the required temperature ranges for transporting perishable goods. It provides a suitable balance between low temperatures necessary for deep freezing and medium temperatures for standard refrigerated conditions. Additionally, R-404A has a good efficiency profile and is compatible with compressor technologies commonly used in mobile refrigeration applications.

R-22 and R-134A are alternatives that may be used in certain systems, but they have limitations in terms of energy efficiency and cooling capacity at the temperature thresholds required in transport refrigeration. R-410A, while efficient for residential and commercial air conditioning systems, does not perform as well in the specific operational conditions of refrigeration systems found in trucks. Hence, R-404A is the preferred choice for this application due to its effectiveness and reliability in maintaining the required cooling environment.