The Construction Specifier, Dec. 2016, by Matt Strong.
https://www.constructionspecifier.com/specifying-hvac-equipment-in-critical-environments/

"Cleanrooms present unique design challenges because they must meet specific requirements that go beyond what is encountered in a typical commercial space. When specifying HVAC equipment in a critical environment such as a cleanroom, engineers must consider the key issues of air filtration, humidity control, and pressurization. While a specifying engineer may have experience with these issues in the context of a traditional commercial application, the considerations are substantially different in a cleanroom."