Are water mist and sprinkler systems equivalent?

YARMOUTH, Maine—Water-mist fire suppression systems aren't just for ships—they are increasingly used in land-based applications, such as historic buildings and hospitals. But are they the equivalent of fire sprinkler systems? That's the question being hotly debated as proposed changes to the National Fire Protection Association's standard on water-mist systems come under review.

A first draft of the changes to NFPA 750 essentially says “a water mist system is now equivalent to a sprinkler system,” Sandra Stanek, NFPA staff liaison for NFPA 750, told Security Systems News.

Water mist systems are similar to sprinklers but emit smaller water droplets. They are considered ideal for ships because less water is released in the event of a fire.

Comments on proposed changes to NFPA 750 will be reviewed at a second meeting on the standard by the Technical Committee on Water Mist Fire Suppression Systems, set for Jan. 29-31 in Palm Beach Gardens, Fla. The meeting is open to the public.

NFPA has received 83 written comments regarding the first draft report, Stanek said. Many of them oppose equating water mist and sprinkler systems.

For example, a representative for Tyco/SimplexGrinnell has recommended in written comments that the two should not be treated as an equivalent. Tyco is a manufacturer of sprinkler systems as well as water mist systems.

Tyco/SimplexGrinnell, which filed an appeal with the NFPA Standards Council on the issue, has argued that “the water-mist fire protection systems designed and installed in accordance with this standard [NFPA 750] are not equivalent in the level of fire protection to a sprinkler system designed and installed in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems.”

The company wants to add language that states: “Sprinkler systems designed and installed in accordance with NFPA 13 provide a reasonable degree of protection for life and property from fire based on sound engineering principles, test data, and field experience. Water mist systems are special protection systems and presently there is no design procedure that would allow extrapolation of test results to different hazards and general hazard types that are included in NFPA 13. Testing to determine the effectiveness of a water mist system to provide protection for life and property from fire should be performed on each separate hazard type and hazard configuration.”

Tyco/SimplexGrinnell has given as its reasons that “almost every building code allows reduction in the passive fire protection requirements because of the history of reliability and fire protection from a properly designed, installed and maintained fire sprinkler system.  This standard needs to differentiate water-mist fire protection systems from fire sprinkler systems so these trade-offs in the building codes will not be mistakenly applied when water mist systems are installed in lieu of a sprinkler system.”

A spokesman for UTC Climate, Controls & Security declined to comment to SSN for this story. UTC Climate, Controls & Security, which owns Marioff, a Finland-based provider of high-efficiency water mist suppression systems, is a unit of United Technologies Corp.

In initial written comments, a representative for United Technologies Corp. recommended equivalency language, stating: “This code proposal is part of a larger group of code proposals to recognize the concept of using water mist systems for protection of structures as a sprinkler-equivalent system. The use of water mist as an automatic sprinkler equivalent is within the systems' listed applications. The proposed additions recognize that based on performance, listings and field experience, water mist is a viable alternative to provide protection for specific classifications of hazards similar to NFPA 13, Automatic Sprinkler Systems.”

In comments for the second draft meeting, a representative for Marioff recommends some amended language. It recommends removing all references to “Ordinary Hazard Group 2” and “Extra Hazard” occupancy classifications in NFPA 750 to ensure that “water mist systems will only be used in occupancies where they have been listed and proven acceptable fire suppression solutions.”

The second draft report on NFPA 750 will be posted for review in July, Stanek said.

The nonprofit NFPA, based in Quincy, Mass., does not itself develop any NFPA standards, but facilitates their development. The documents are developed by the technical committees that are made up of experts who represent a variety of stakeholder groups in the industry.