After conducting a search, I found that "IEST-RP-CC003.3" appears to be a standard related to cleanrooms and controlled environments. IEST (Institute for Environmental Sciences and Technology) publishes guidelines and standards for contamination control and cleanroom practices.
If you're looking for information on the IEST-RP-CC003.3 standard, here's a brief overview: iest-rp-cc003.3 pdf