There is no GMP requirement in the EU and PIC/S (i.e. TGA) GMP guidance’s for the manufacture of non-sterile medicinal products in a “clean room”, but we do use clean areas that are effectively ventilated with filtered air where the products or open clean containers are exposed. On the other hand, for the manufacture of sterile medicinal products, clean rooms are mandatory, as defined in Annex 1 of the EU and PIC/S GMPs. This Annex defines a number of additional requirements besides the airborne particulate concentration limits used to classify clean rooms.
In a nutshell, if you manufacture a non-sterile medicinal product, you should be very careful about classifying or grading your clean areas, for example, classifying a room as “Grade D”. Whilst not a code requirement, many regulators, like the Australian TGA will expect you to fully comply with all of the requirements for a Grade D room as defined in Annex 1, even if it’s not a GMP code requirement. If you have classified the room as Grade D, you will need to live with the consequences and costs of maintaining this level of clean room cleanliness during operation.