Following a tragic fire in a Las Vegas hotel in the 1980’s, the industry recognized the dangers to occupants from smoke inhalation during a fire emergency. This spurred the development of a series of codes and standards, including NFPA 92A and 92B, intended to provide a method to control the spread of smoke and to provide safe passage for occupants out of the building during a fire emergency.
We often refer to the resulting systems as “engineered smoke control,” which generally utilizes a combination of dedicated fans and dampers as well as non-dedicated systems that are normally used for providing occupant comfort. The controls for smoke control systems are critical, and they require special consideration including connections to the building fire alarm system, regular testing, and in some locations, special agency (UL) listing. This month we are going to examine how to upgrade or replace controls and BAS in a building that may have partial or fully-engineered smoke control.
Reverse engineering to get ahead
The first step is to determine what, if any, smoke control systems are currently in place. These systems are generally applied on buildings that are considered “high-rise” (usually over six floors) or “atrium,” where there is a central area open across several floors. You will also find these systems in other buildings such as hospitals, theaters, arenas, and other types of public assembly areas. The best way to document existing systems is to go back through the original design documents and control drawings. These will often provide valuable details as to what was originally installed. If these documents are missing, then the sequences must be determined through system testing and observation of how they operate in reaction to an alarm input.
The second step is to reverse engineer what is in place and to clearly document the current sequence. This information should then be reviewed with the local Authority Having Jurisdiction (AHJ) and a request made to replicate the existing system logic as the system is upgraded. In many cases, the system that may have been installed 20+ years ago may not conform to current code, but most code officials are willing to “grandfather” in these systems and not require a complete re-engineering of the system.
The third step is to make sure that the proper sequences, products, and tests are included as part of the new design. Special care is necessary to meet the requirements related to engineered smoke control, and the contractor needs to use caution so that both the new and old systems are operable during the retrofit. As part of commissioning, we require special tests of the smoke control sequences to verify that they do respond properly to the fire inputs, overrides, etc., and that the system works as intended. The AHJ may have special testing requirements including the use of smoke tests.
The retrofit of a project with smoke control is something you should approach cautiously as they require additional design work, documentation, coordination, and testing. In the most extreme cases, they may require conformance to UL-864-UUKL, which requires entire special systems to be provided. We would recommend that you make the owner aware of these risks and consult early and often with the AHJ.
