Life Safety: Standard Procedure
Editor’s interview with Robert Solomon, P.E.
Thanks for joining us, Mr. Solomon. It seems like 2009 has been unusually busy in terms of publishing revised standards. Would you start with NFPA 90A, giving us a quick overview and a look at what’s changed?
The past year really has been active period in terms of the tremendous effort that has been put in by the NFPA Technical Committee Members who work on the five standards we are talking about. NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating Systems, 2009 edition provides a series of requirements for construction, installation, operation, and maintenance of systems for air conditioning and ventilating, including filters, ducts, and related equipment, to protect life and property from fire, smoke, and gases resulting from fire or from conditions having manifestations similar to fire.
The 2009 edition has been updated to refine and recognize new criteria in a number of areas, most notably those dealing with the types, quantities, and permitted use of various materials in plenum spaces. Specific criteria have been provided to govern materials such as plenum cable, the type of cable, and the test protocols to determine the fire and smoke characteristics of the cable and wiring components. These changes have helped to define the areas of responsibility between NFPA 90A and NFPA 70®, National Electrical Code®, with regard to this issue.
In addition, the requirements for the maintenance of fire dampers have been removed and replaced with a reference to NFPA 80, Standard for Fire Doors and Other Opening Protectives, where such requirements now reside. A reference to NFPA 105, Standard for the Installation of Smoke Door Assemblies and Other Opening Protectives (also discussed below) for the maintenance of smoke dampers was also added. These types of changes help to ensure that once any of the required systems are installed, they are maintained for their life cycle.
And on to the new version of NFPA 90B, dealing primarily with a reference update?
NFPA 90B, Standard for the Installation of Warm Air Heating and Air-Conditioning Systems, 2009 edition provides a series of requirements for construction, installation, operation, and maintenance of systems for warm air heating and air conditioning, including filters, ducts, and related equipment to protect life and property from fire, smoke, and gases resulting from fire or from conditions having manifestations similar to fire.
The 2006 edition included changes to update terminology for materials used as part of the regulated system. This included revising the term “flame spread rating” to “flame spread index.”The major change in the 2009 edition was to replace the references to NFPA 255 with ANSI/UL 723 and ASTM E 84, as NFPA 255 is in the process of being withdrawn. All three test standards are quite similar with regard to the test protocols used to determine flame spread indices and smoke developed indices.
When it comes to NFPA 92A, it looks like the changes are more substantive in terms of the relation to between the science of smoke generation and movement and the actual smoke control design approaches and methods.
NFPA 92A, Standard for Smoke-Control Systems Utilizing Barriers and Pressure Differences, 2009 edition provides a series design criterion and parameters to establish pressure differences at some defined boundary or space in a building in order to manage and control the movement of smoke. While many of the changes in the 2009 edition are editorial, they worked to improve upon the understanding of the revisions from 2006 that were quite vast.
New provisions for the power supply requirements and configurations and arrangements of the control systems were implemented. These changes work to increase the reliability of the systems and clarify the various modes of operation (manual, automatic) as well as methods to shutdown and override the system. Design pressure differences were added based on sprinklered and unsprinklered buildings plus differing ceiling heights.
Design requirements for pressure differences were also included based upon the position (open or closed and the number) of stair doors. The system design must account for this configuration while at the same time allowing the stair doors to be opened in the direction of exit travel within the force limits that are required by code. All of these related design details are critical to make sure the system works to maintain a tenable environment during the period needed for the occupants to evacuate the affected areas of the building.
This next standard, meanwhile, focuses on better tools to help the engineer with the somewhat intricate calculations that dictate the system performance.
NFPA 92B, Standard for Smoke Management Systems in Malls, Atria, and Large Spaces, 2009 edition provides a series of criterion and parameters for the design, installation, testing, operation, and maintenance of new and retrofitted smoke management systems for the management of smoke within the space where the fire exists, or between spaces not separated by defined smoke barriers.
The 2009 edition includes changes that specify design criteria to maintain tenable spaces, provision for plume design for a variety of geometric configurations, and a method to calculate smoke densities. This edition also incorporates the Tentative Interim Amendment (TIA) issued for the 2005 edition, which modified a number of the equations. Maintaining a tenable environment in large spaces requires the designer to utilize methods that keep the smoke layer interface height at a level that allows the occupants to safely leave the space. NFPA 92B contains a series of equations and parameters that allow the designer to calculate fire size, smoke layering and smoke movement. These equations focus on topics such as heat release rates and air velocity values that mix in the plume in order to determine the appropriate volume of makeup air to satisfy the design goals.
And finally, NFPA 105 looks like it received a name change as well as some updates.
NFPA 105, Standard for the Installation of Smoke Door Assemblies and Other Opening Protectives, 2010 edition provides minimum requirements for smoke door assemblies for use in providing safety to life and protection of property from smoke by restricting the movement of smoke through door assemblies. These requirements work together in order to maintain a tenable environment. The 2010 edition also includes inspection, testing and maintenance of the assemblies.
The 2010 edition of NFPA 105 contains revisions to the testing requirements for smoke dampers. Through the addition of annex text, the revisions change the requirement of damper actuation and cycling (as part of the associated smoke detector testing) to be in accordance with NFPA 72, National Fire Alarm Code as an optional provision, not a mandatory requirement as in previous editions. The title of the document was changed to Standard for Smoke Door Assemblies and Other Opening Protectives in order to recognize its expanded scope of subjects that are now covered.
(Ed. note – Readers can purchase all of these Standards, either as hard copies of in PDF format, by going to www.nfpa.org and selecting the “Buy NFPA Codes & Standards” tab on the left. NFPA members get a discounted rate on those purchases.) ES