Simply supplying a dry pipe fire sprinkler system with nitrogen gas will not control oxygen corrosion. A vent is required to remove oxygen so that the sprinkler system can be resupplied by supervisory nitrogen gas. Currently, there are two primary methods of venting oxygen from dry pipe fire sprinkler systems:
Fixed pressure drop venting
Fill and purge breathing
Only one of these methods completely eliminates oxygen before it can react with metal fire sprinkler piping: fill and purge breathing. In contrast, fixed pressure drop venting cannot completely remove all the oxygen from remote portions of the sprinkler system because the nitrogen gas takes the path of least resistance to the vent.
No Remote Vents in Critical Areas
Use of the fill and purge breathing process allows for placement of a single vent anywhere on the piping network because the dynamic mixing of gases creates a homogeneous gas mixture prior to exhausting from the vent during the purge cycle. This flexibility is particularly important in mission critical facilities, such as data centers, where building owners and operators do not want equipment that presents any leak risk installed in critical areas. Fill and purge breathing allows the vent to be installed at the sprinkler riser on any dry pipe or preaction fire sprinkler system.
The video below illustrates the differences between the fill and purge breathing process used by ECS and fixed pressure drop venting used by others.