A modern four-co~or rotary printing plant requires careful control and monitoring both of environmental conditions and of relative pressure between the printing morn and the operating personnel area. This paper describes the system installed and successfully tested at the printing plant of a leading Italian publisher.

The basic concepts of the HVAC system and a description of the control hardware are given: the six airhandl ing units are controlled via a direct digital control (DDC) system featuring remote intelligent panels and centralized personal computer with monitoring functions.

While the available standard DDC software was adequate for temperature and humidity control, special routines had to be developed to account for six different modes of operation in order to keep relative room pressures within the specified range. Flow diagrams outlining these modes and the program flow chart are presented.

The paper concludes with an overview of the prob- lems encountered in the first months of operation and some final considerations on the impact of DDC on the printing industry.