The Federal Code of Regulations Section 21 parts 211.42 states:
Any building or buildings used in the manufacture processing, packing, or holding
of a drug product shall be of suitable size, construction and location to facilitate
cleaning, maintenance, and proper operations.
If you look that statement it refers to Airchanges, Dust control, Humidity control, Lighting , Material movements and Temperature control.
Not all products are stable at all temperatures and even during packing humidity must be controlled for some products.
This can be only achieved when the Packing area is atleast Class 100000 or Class 8 in Tropical countries.