Introduction

There are now commercially available fire suppression systems that are described as “hybrid” systems, but are not addressed in the NFPA standards. These systems are unique because they use an inerting gas such as nitrogen as well as fine droplets of water (or clean agent) typical of water mist system. FM Global has developed Approval Standard 5580 and determined that the oxygen concentration is not depleted enough to classify this as a clean agent, but it also does not show all of the same characteristics as a standard water mist system. In some cases, manufacturers are “mixing and matching” requirements for water mist systems and inert gases to suit their needs.

The objective of this project was to provide background information on hybrid fire suppression systems so that it can be ultimately determined where these systems should best be addressed within NFPA documents. These systems may fit in NFPA 750, Standard on Water Mist Fire Protection Systems, NFPA 2001, Standard on Clean Agent Fire Extinguishing Systems, or may be unique enough to require their own independent document.