The Role Of A Special Inspector For Smoke Control Systems
The goal of these systems is to provide a smoke-free environment for occupants to safely evacuate or relocate to a smoke-free area. The facility with smoke control is also required to be "fire" alarmed and fully sprinklered. International Building Code (IBC) 2000, Section 909.3, requires that smoke control systems be subject to special inspections and testing to verify the design and operation of the installed system. The special inspections duties and tasks are similar to commissioning.
The Special InspectorThe IBC 2000 909.3 and 1704.14 describes the duties and the qualifications for a special inspector. The key point is for the special inspector, individual, or agency to have the specialized knowledge of multidiscipline design comprised of ducted air, fire alarms, and fire sprinklers. The special inspector is an expert that assists the projects' team to verify a working code compliant system. The special inspector should be a licensed professional engineer with fire protection (sprinkler) design experience and the ability to manage the testing and balancing of the installed equipment. The project team is composed of the client, the designer, the various local code officials, the installing contractors, and the insurance underwriters. The special inspector should not design the system or replace the inspections of the various code officials during design and construction.
The SystemsA smoke control system is an air-ducted system with fans, dampers, and the appropriate controls. The alarm and activation systems are the fire alarm and water flow in the fire sprinklers. Building security systems are used to alert security personnel and the fire department.
The systems are powered by normal and emergency power. Communication be-tween the systems is by a fan-damper control interface, sprinkler alarm interface, and building security interface.
The following is a list of the typical system parts:
- Fans - supply and/or exhaust;
- Airflow paths through ductwork, dampers, louvers, intake/exhaust hoods, and doors;
- Fire command control panel;
- Sprinkler zones and flow switches;
- Fire alarm zones and detection types; and
- Security system calling, messages, and door lock control.
Design ReviewThe special inspector shall review the system design relative to the code requirements, discussing system design method with the authority having jurisdiction (AHJ) and the client. The design engineer should provide the calculations for cfm capacity at an early stage of the project.
During the review or discussion, a decision should be made relative to which power, alarm, and control systems must be installed in conduit, and which can be in plenum-rated cable.
The physical barrier zones, the fire alarm zones, and the sprinkler zones must be coordinated to all reflect the same coverage.
Construction Phase ObservationA meeting should be scheduled early in the construction to communicate to the various subcontractors the expectations for their involvements in the smoke control system. An important message to the electrical subcontractor is to have the smoke control components wired up early for normal and emergency power. Coordinate a construction schedule with the general contractor.
PretestingThe purpose of this phase is to avoid surprises at the time of acceptance testing. Acceptance testing often occurs close to the sign-off date for occupancy. Many other client tasks depend on this occupancy date. Therefore, pretest and complete the acceptance list as soon as possible. A duct leakage pressure test at 1.5 times the designed pressure should be done using duct caps before grilles, registers, and diffusers are installed. Review the fan shop drawings for the required fan temperature ratings and the 1.5 times number of required drive belts with a minimum of two drive belts. Have the electrical contractor check the phase wiring between normal and emergency power. This is important to prevent fans from operating backward under emergency power. Verify that the security system that normally locks doors unlocks them when the smoke control system is activated. Also, verify lock operation on emergency power.
Team CommunicationThe team should receive a copy of an event/action matrix as shown as a simple example on Figure 1. This matrix is based on the system design and AHJ acceptance.
Acceptance TestingDuring the pretest, the system can be activated by puffer smoke or a magnet to simulate a fire alarm. The sprinkler flow switch can be manually tripped to simulate water flow. However, during acceptance testing, the pass/fail criteria is pressure differentials across the zone or door barriers, door pull forces that do not exceed 30 pounds, a copy of the TAB report to verify the cfm, and operational verification of all the dampers. However, it is often requested to provide a "smoke show" to indicate that the smoke is controlled. Provide a hot rising thermal plume using a heat source and chemical smoke. In small systems, real smoke can be generated in a galvanized trashcan with a cover that controls and stops the smoke. Burning of wet cardboard works well in this trashcan and simulates a small fire.
The Report and CertificationThe report, which is written by the special inspector and signed by the design engineer, confirms that the system meets the design intent.
The report should document the design intent, the system description, schematic diagrams, the measured pressure test values, the airflow TAB report, the pass/fail criteria, pretest memos, installation equipment photographs, and the conclusion. Copies of the report should be filed with the code authority, the client, the design engineer, the responsible contractor, and the special inspector.
What Goes Wrong?The following is a list of common problems that occur during pretest and sometimes appear at the acceptance test.
- The fan produces too much or too little cfm and/or pressure;
- The barriers are not constructed reasonably airtight;
- Installation screws block damper operations;
- Fire alarm system software is not correctly programmed;
- The smoke detectors are too close to the supply diffusers, and the real smoke will not alarm the system; and
- Fan motors overheat and will not restart.
SummaryA smoke control system is an integrated multidisciplinary system. Its successful operation depends on the team's understanding the interrelationship of the components. Each contractor and code official can install and observe his piece of the smoke control system. However, the special inspector is the commissioning agent who verifies that the system is designed correctly and does operate to the design intent.
The special inspector is required by code, is contracted directly with the client, is involved early in the project, and checks and tests all through the project to avoid a surprise or delay at the point of occupancy sign-off. ES
1. International Conference of Building Code, Uniform Building Code, Sections 402 and 905.