Ammonia, scientific name "Freon", is a refrigerant, that is, a medium for transferring heat in air conditioning and refrigeration systems. Without it, the air conditioner can't cool. However, this refrigerant is a stable substance and is not a consumable in air conditioning. Xu Dehua said that the maintenance master usually judges whether the air conditioner is ammonia-free by checking whether there is a difference between the set temperature and the outlet temperature and whether the thin tube valve of the external machine is frosted.