Area classification requirement for Ampoule Washing

Can any one give reference for wahing of ampoules falls in which category either C or D???

Ampoule washing should be done in C grade area.WHO guideline

I was searching but couldn’t find in written…

If washing of ampules area are class D ? can we justify.

Washing prior to heat sterilization, Process barrier; Unidirectional Airflow, Process background; D

Sir,can u please explain briefly about ABCD .
Thank you