Nearly all guidelines addressing the requirements with regard to HVAC systems or air qualities focus on the manufacture of sterile medicinal products. This is especially true for the Annex 1 of the EU GMP Guideline.
The WHO now published a revised working document of the guideline for public consultation which specifically addresses the requirements for HVAC systems used during the manufacture of non-sterile pharmaceutical dosage forms. The version valid so far dates back to 2011 and is contained in the WHO Technical Report Series, No. 961 as Annex 5 (Supplementary guidelines on good manufacturing practices for heating, ventilation and air-conditioning systems for non-sterile pharmaceutical dosage forms). The main changes are the integration of sample layouts (such as for weighing and dispensing) in the chapter "Premises" and a revision of the chapter "Commissioning, Qualification and Validation". Furthermore, a separate chapter now is devoted to maintenance.
You can find the current draft of the "Guideline Supplementary guidelines on GMPs for HVAC systems for non-sterile pharmaceutical dosage forms" in the members' area of the ECA website.