This document describes general engineering guidelines to be applied to ensure that buildings, individual equipment items and accessibility of equipment when integrated within the plant layout are designed so that aspects of the process operation, cleaning and maintenance comply with hygienic design standards. It details requirements related to plant enclosure, including hygienic zoning, building structures and elements (from floor to ceiling) as well as process line installation. Attention is also given to air stream and water related aspects within the plant as well as cleaning and contamination aspects. See also Doc 22.