Chapter 15: Management and Control of Smoke and Fire

15.1. Theory and Applications. 1

15.2. Commissioning Smoke and Fire Management and Control Systems. 3

15.2.1. Functional Testing Benefits

Key Commissioning Test Requirements

Key Preparations and Cautions

Time Required to Test

15.3. Testing Guidance and Sample Test Forms. 6

15.4. Supplemental Information. 6

15.4.1. Coordination. 6

15.4.2. Certification Test6

15.4.3. Leakage. 8

15.4.4. Door Opening Forces. 8

15.4.5. Piping and Condensation Protection. 8

 

15.1. Theory and Applications

While simple in concept, making a smoke control cycle work involves the coordination and interaction of just about every trade involved in the project, and the solutions to potential problems can be both subtle and complex. Major reasons behind the complexities of commissioning a smoke control system are described below.

·       For the proper pressure relationships to be achieved and maintained during the smoke control cycle, the building envelope and various compartments must be relatively airtight. This requires significant attention to the details of construction and sealing by trades such as carpenters, masons, steelworkers, and dry wall installers, all of whom do not typically think of their work as being associated with the successful performance of the mechanical system.

·       The fire and smoke detection command and control logic is often split between the fire alarm system and the HVAC control system. The fire alarm system has the inputs required to determine the state of a fire and the smoke it might be generating in the building. The HVAC control system directly interfaces with the mechanical systems that may be used by the smoke control process, but the HVAC control system typically relies on commands from the fire alarm system or manual inputs from the firemen responding to the fire to determine the proper state of the various fans and dampers.

·       The numerous components associated with making the smoke control system work are located all over the facility. These components are often in difficult to access or concealed locations. Testing requires multiple parties stationed at multiple locations, all of whom are capable of understanding and communicating the status of various components to the test coordinator.

·       Extended operation in the smoke control or fire mode, as is often the case during initial commissioning or re-testing can subject the building and its occupants to conditions that can cause discomfort or damage in some cases. Careful monitoring of the smoke control process during testing is essential to prevent unanticipated damage to the envelope, the building’s systems, or the building’s contents.

·       Barometric pressure and stack effect in a high-rise building can affect the test results given the relatively low pressure differentials that most smoke and fire management systems operate under.

Because of all of these factors, false starts and numerous repeat tests are the rule, rather than the exception during smoke control system testing. The process of testing theses systems can take considerable time, both during initial testing and the retesting cycles that must occur to ensure the operational readiness of the smoke control systems. When working with these systems, either in a new construction environment, a facilities operations environment, or a retrocommissioning environment, the people involved in the testing need to take all of these factors into consideration and set their time and resource budgets accordingly.

Fire and smoke management systems are employed as life safety systems and are often dictated by code requirements for certain building types, sizes and configurations. In process and production environments, they can be employed to protect machinery and the area surrounding a fire from contamination and to provide a clean and clear path for the fire fighters to extinguish the fire quickly. It is not unusual for these smoke control requirements in production environments to be driven by insurance requirements rather than code due to the capital liability represented by loss of production and/or damage to equipment that could result from even a small fire. For instance, many clean room facilities have extensive smoke management systems because adjacent processes could be severely compromised by relatively small amounts of the contaminants generated in a fire.

Smoke and fire management and control systems generally provide some or all of the functions outlined in the following paragraphs. In some situations, the process is an automated cycle controlled based on inputs from smoke detectors and other components in the fire alarm system. In other situations, it is simply a manually initiated process controlled from a fireman’s command and annunciation panel located somewhere in the main entry space of the building. A more detailed treatment of the subject can be found in the ASHRAE Applications Handbook and the ASHRAE Principles of Smoke Management.

Fire Management

Fire management is typically provided by compartmentalization using fire rated assemblies like the walls and floor to contain the fire in a given area for some defined interval of time. The HVAC and mechanical trades must interface with this compartmentalization any time their systems penetrate them. All penetrations must be sealed or otherwise protected to maintain the integrity of the fire separation. Typically this is accomplished by fire-stopping around the penetrating system and, in the case of ducts, by providing fire dampers that will contain the fire on one side of the separation.

Smoke Management

Smoke management systems are designed to modify, dilute, redirect, or otherwise influence the movement of smoke in a building experiencing a fire, but not necessarily to control it or limit its movement.

Smoke Control

Smoke control systems are intended to limit and control the movement of smoke during a fire. The most common approach involves pressurizing the areas on either side of the compartment where the fire is located and exhausting the fire area. This method creates a ‘pressure sandwich’ which tends to move air (and thus smoke) from the protected areas towards the fire and move smoke out of the fire area. While this does introduce fresh oxygen to the fire area, most systems are aimed at protecting the occupants and equipment in the adjacent compartments to allow evacuation and to allow firemen to gain clear access to the fire to extinguish it. The fire management techniques, equipment, and constructions employed around the fire compartment are relied upon to contain the fire rather than smother it by denying it air, which often will increase the smoke generated.

Stair Pressurization

Stairwells are frequently the primary escape routes for the occupants of a building in a fire emergency. In addition, the stairwells may be the primary access routes for the fire fighting teams responding to the emergency. Thus, it is critical that they remain clear of smoke for as long as is necessary to safely evacuate the building and bring the fire under control. Most high rise buildings employ a stairwell pressurization system to keep the stairs clear of smoke while operating at a low enough pressure that an average person can open the doors to enter or exit the stairwell on their way to safety.

Elevator Pressurization

Most elevator pressurization systems are designed to allow the elevators to be used by the fire fighting team responding to the fire. However, some efforts have been made to design systems to protect elevators to a level that would allow them to be used for the evacuation of handicapped individuals. While small amounts of smoke may be tolerated in the elevator if it is being used to fight a fire, smoke in an elevator used for evacuation purposes is unacceptable. In addition, if the elevator is being used to evacuate the entry and exist paths to the elevator also need to be kept free of smoke. In both instances, the piston effect created by the elevator moving up and down the shaft can cause significant problems in controlling smoke in the elevator cab and in the areas adjacent to the shaft.

15.2. Commissioning Smoke and Fire Management and Control Systems

Due to the customized nature of smoke control systems, most test procedures will need to be developed as custom procedures for the project in question using components from the information available here and in the CTPL. The time to do so should be taken into consideration when developing the budget for commissioning this type of system.

The following tables outline the benefits and background information associated with testing smoke and fire management and control systems. Refer to Functional Testing Basics for guidance related to all functional testing activities, regardless of the component or system being tested.

15.2.1. Functional Testing Field Tips

Key Commissioning Test Requirements

Fire-Smoke Damper Test Goals

The objective of testing Fire and Smoke Control Systems is to ensure that each of the components of the system is working correctly, and that they work together as a system according to design intent and governing codes. The system must detect fire events, prevent smoke migration and circulation, and maintain proper pressurization of building spaces, including stairwells and elevator shafts. In most instances, it will be necessary to successfully demonstrate the operation of this system to the City Fire Marshall to obtain an occupancy permit. In some cases the engineering representative from the insurance underwriter will also have significant input in acceptance or rejection of test results.

1 Verify all fire-smoke damper prefunctional checklists are complete. Prior to performing any functional tests, the commissioning pre-start, start-up, and Prefunctional Checklists and applicable manufacturer's pre-start and start-up recommendations should be completed.

2 Verify system operates as intended under both normal and emergency power as required. When testing system operation under emergency power, it is best to disconnect normal building power at the main service disconnect to simulate true emergency power operating conditions. Attempt to coordinate all other emergency power tests for the same time to minimize runtime on emergency generators.

3 Verify proper damper operation. The smoke damper may be utilized in either a "passive" or "engineered" smoke control cycle. The passive cycle is when the damper is closed to prevent smoke from migrating through the duct across a smoke barrier and the supply fan is typically shut off. An engineered smoke cycle actively controls various dampers and fans to contain smoke within the event zone.

4 Verify damper position indicator switches (if present) operate properly.

5 Verify temperature response device(s) operate properly. A fire or combined fire-smoke damper will shut the damper automatically when temperature exceeds the installed closure device fixed temperature setting.

Engineered Smoke Control Cycle Test Goals

1 Verify all component prefunctional checklists are complete. An engineered smoke control cycle is designed to prevent the migration of smoke by maintaining air pressure differentials between the event zone and rest of the building. Typically the pressure differentials are created by actively controlling various smoke dampers and the building's HVAC system and/or dedicated fans. Prior to performing any functional tests, the commissioning pre-start, start-up, and Prefunctional Checklists on all fan systems and dampers should be completed, as well as applicable manufacturer's pre-start and start-up recommendations.

2 Verify proper sequence of operation. In most systems, all air handling units will shut down and smoke dampers will close upon an alarm condition. Operation of individual fans and dampers is then initiated manually by fire personnel or the "authorized operator" of the smoke control management system.

3 Verify proper operation of the smoke control cycle. Initiate an event signal and verify that all HVAC fans shut OFF and all smoke dampers close, all individual fans and dampers respond appropriately to the desired positions when commanded, and pressure differentials are maintained. Note that stack effect; wind speed and direction and outdoor temperature may all influence measured pressures and system balance.

4 Verify proper operation during stairwell and elevator shaft pressurization tests.

Key Preparations and Cautions

1 Perform practice runs of the test prior to calling the inspectors for certification. While simple in concept, smoke control systems are operationally complex and generally will take several test runs to find and correct all of the bugs and achieve reliable results.

2 Use extreme caution when performing a test during subfreezing weather. Many control sequences assume that if a fire were to occur, then sacrificing cooling coils and plumbing to freezing is an acceptable compromise in the interest of life safety and property protection. During testing, subfreezing air can quickly damage equipment and systems, making a return to normal operation difficult or impossible following the test.

3 Many smoke control cycles involve closing dampers against moving air streams and creating strong pressure gradients between various portions of a building. These pressures can cause problems with unanticipated opening and closing forces on doors and air hammer, especially the first time the test is run due to improper adjustments and bugs in the system logic.

Cautions

Depending on the response time of individual components, static pressure within the duct may exceed design limits and possibly result in a catastrophic failure. Ensure the smoke control strategy is sequenced to prevent physical damage to fans, dampers, ducts, or other equipment.

Virtually every engineered smoke control cycle requires that air handling units bring in 100% outside air in order to pressurize zones surrounding the event zone. The following precautions will help minimize potential problems or catastrophic failures during testing:

Most codes require that the freezestat safety be by-passed when an air handling unit is in smoke control mode. Hence the pre-heat and/or heating coil(s), as well as the heating system, must be functioning in order to prevent the cooling coil from freezing if the smoke control cycle is tested during sub-freezing conditions. Note that most pre-heat or heating coils are typically not sized to handle 100% sub-freezing outside air, hence coil size should be checked during design review to ensure the coils will be big enough to at least prevent the unit from freezing during an actual smoke control management event.

Along the same lines, if the smoke control cycle is tested during extremely hot conditions, the cooling coil(s) as well as the entire cooling system must be functioning in order to prevent the space temperature from getting out of control. Elevated building temperatures during testing could have adverse impact on workers, equipment, or building materials.

Test Conditions

The building envelope needs to be substantially complete for the area to be tested. An incomplete envelope can cause problems with achieving the required pressure relationships that may cause the test to fail due to no fault of the mechanical systems.

All related systems should be completely operational. Interlock wiring and programming between the fire alarm system and control system needs to be fully functional and verified, as well as the interlocks between the control system and the mechanical equipment associated with the cycle.

Instrumentation Required

Instrumentation requirements will vary from test to test but typically will include the following instrumentation in addition to the standard tool kit listed in the Functional Testing Basics:

1 Heat gun and a digital or infra-red thermometer.

2 A duct leakage testing machine or blower door test set-up can be useful for troubleshooting compartments with excessive leakage rates. This instrument is often available from the sheet metal contractor, but may require certification if it has not be certified recently.

3 Inclined manometers, Magnehelics., Shortridge Air Data Multimeters., and other instruments capable of measuring and documenting low air static and velocity pressures.

4 NFPA Codes 90A and B as well as any other applicable codes governing the installation on a particular project.

5 A complete set of mechanical system, fire alarm system, and smoke control system drawings including a detailed narrative of the required operating sequence.

6 Multiple pairs of walkie-talkies are invaluable for performing this type of testing, especially in large buildings where multiple parties need to report results from a variety of locations.

Time Required to Test

The time required to test will vary from several hours in buildings with a few simple functions like elevator and stair pressurization to several days or weeks for a complex building with a complex smoke management or control cycle. Much coordination is required and many components must interact reliably for the test to be successful.

 

15.3. Testing Guidance and Sample Test Forms

Click the button below to access all publicly-available prefunctional checklists, functional test procedures, and test guidance documents referenced in the Testing Guidance and Sample Test Forms table of the Air Handler system module.

AHU Testing Guidance and Sample Test Forms

15.4. Supplemental Information

The following information is intended to provide general guidance for functional testing of smoke and fire management and control systems.

15.4.1. Coordination

As indicated earlier in this chapter, fire and smoke management systems will often engage nearly every trade involved in the project. This involvement can be in the form of direct participation in the installation and start-up of the systems, or it can be indirect in the form of providing structures, construction, and management that will support the successful operation of the systems.

15.4.2. Certification Test

In most instances, the certification of the smoke and fire management and control functions will be one of the final steps in obtaining an occupancy permit. Without the occupancy permit, the owner will not be able to use the facility. If the owner cannot use the facility when anticipated, the following problems can arise:

·       Delayed move-ins by tenants may lead to financial recourse against the owner if the tenants have liquidated damage clauses included in their lease agreements

·       Delays in projects where work in one section of the building is contingent upon completion of another section so business functions can be moved to accommodate the construction.

·       Delays in production.

All of these factors make timely procurement of the occupancy permit, and thus, timely certification of the smoke and fire management and control systems of paramount importance. There may be ways to work around unfinished drywall, sensor calibration problems, and final balancing, but if you aren’t able to successfully certify the life safety systems, you won’t be getting an occupancy permit.

For these reasons, those responsible for testing the smoke and fire management and control system should consider the following strategies:

·       Anticipate several test cycles and plan the testing schedule accordingly. Because of the extensive coordination required between people and systems to achieve reliable smoke and fire management and control system operation, it is wise to anticipate that more than one test effort will be required to achieve the desired results. Even in a well-coordinated test, where all of the parties have made a concerted effort to prepare the portion of the system they are responsible for, a nuance may be missed. For this reason, it is seldom a good idea to invite the code official to be present for the first test of a system, especially a complex system.

·       Determine which systems are critical to successfully performing the test. Make sure these systems are on the critical path for completion prior to the first scheduled test date.

·       Determine if there are any environmental conditions that would preclude extensive testing in the smoke management and control mode. For example, if systems are not capable of handling 100% outdoor air at temperatures below freezing safely, then functional testing and certification testing the systems in the winter months could be extremely difficult. Similar considerations apply to systems in hot and humid environments in the summer. These outside conditions may prevent the testing necessary to meet the construction and occupancy schedule. If these conditions exist, they need to be brought to the team’s attention and resolved while there is still some flexibility in the schedule. The day of the certification test is the wrong time to bring up how the ambient conditions will affect the testing.

·       Develop a procedure with system diagrams that describe the test sequence in detail. Use this procedure in planning meetings with all parties involved to define responsibilities and clarify expectations. Use this plan during the actual testing to document the test results.

·       Plan on completing the final certification test well in advance of the scheduled date of occupancy and the date upon which the final inspection for an occupancy permit will occur. Based on schedule changes, adjust the testing schedule accordingly or advocate against the change if it will not provide sufficient time for the test plan.

On a 13 story high rise building, the design-build mechanical contractor was having a difficult time pressurizing the stairwells. Frustrations and tensions were mounting because adjustments that ran the pressurization fan motors up to the limits of their service factor still were not producing the desired results. Time was running out if an occupancy permit was to be secured and the tenants were to be allowed to move in on schedule. Many of the new tenants would not have any office space if they were not allowed to move in on schedule. An engineer for the mechanical contractor noticed that an architectural detail relating to how the shaft wall met the slab and structural steel in the stairwell at each floor resulted in a 1/4’ to 1/2’ crack all the way around the perimeter of the stair shaft at each floor. When he pointed this out as a potential reason that the stairs were not pressurizing, the general contractor’s foreman chuckled and said, ‘A quarter inch crack just ain’t that important kid.’ The general contractor changed his mind after a quick calculation revealed that the net area associated with the crack was 20 to 30 square feet when the perimeter at all floors was taken into consideration. That was the same as having two of the stairwell doors standing wide open all of the time. Caulking the crack solved the pressurization problems and the fans were returned to the original speed settings specified by the designer.

15.4.3. Leakage

Having a leaky compartment can make achieving the required smoke control system test results difficult, especially in the case of stairwell pressurization systems. Small details related to the construction of the stairwell can have significant impacts on its rate of leakage. If a compartment will not pressurize, performing a leakage test and a detailed inspection for leakage paths may be advisable before speeding up motors or ordering larger motors.

15.4.4. Door Opening Forces

With positive pressure relationships in the stair towers and potentially negative pressure relationships established on the fire floor by the ‘pressure sandwich’ used to control smoke, the force required to open a door to the stairwell can become significant. The concern is that someone might not be able to open the door against the pressure differential induced force, and thus would be unable to enter the stairwell. Most codes restrict this force, which often requires that a pressure control system be provided for the stairwell. Inspectors often want this stairwell pressure control system to be demonstrated as a condition of acceptance, selecting the fire floor and doors to test at random. Prior to the inspector’s test, it is advisable to have placed the system in the worst-case operating mode and then tested the door-opening forces. Verifying the exact technique that the inspector will be using to measure the force may also be desirable, since the results can vary depending on the measurement method. This verification process may involve setting up the ‘pressure sandwich’ on every floor and then testing all doors, which can be time-consuming.

15.4.5. Piping and Condensation Protection

Many smoke and fire management and control systems use the HVAC air handling equipment to provide the make-up and exhaust air capacity required for the smoke control and management functions. Usually to meet these air flow requirements, the system is placed in a 100% outdoor air operating mode. While this mode of operation may be normal for the system when it is on an economizer cycle, many HVAC systems serving office buildings do not have the preheat capacity or coil piping configurations to allow them to handle 100% outdoor air safely when the outdoor air temperatures are below freezing. It is not uncommon for the design philosophy in these situations to be that the water coils will be sacrificed if necessary in the interest of life safety, and the control system actively jumps out the freezestat during the smoke cycle. While this concept is reasonable in the context of a real fire, it is worthy of careful consideration in the context of smoke and fire management control system testing and false alarms.

While it is unlikely that most buildings will experience a fire event of sufficient magnitude to trigger a smoke management and control cycle in the course of their operating life, it is highly likely that they will experience a false alarm that will trigger the cycle. This event could occur on the coldest or hottest day of the year or when nobody is in the building to respond to the problem in a timely manner. As a result, one or more of the following situations may occur:

·       If it is below freezing, the water coils in the unit may freeze. Freezing can occur in a matter of minutes. If it is extremely cold, the water can freeze even if the circulating pumps are operating. If the system remains in this mode for an extended period of time during subfreezing weather, plumbing and sprinkler lines in the building can freeze, especially lines in close proximity to supply diffusers or in the path of infiltration that might be caused by the 100% exhaust portion of the control cycle.

·       If it is warm and humid outside, the introduction of significant volumes of hot and humid unconditioned air into the building can result in water damage from condensation, especially if the chilled water plant or cooling system was off-line when the problem occurred. When the humid air comes in contact with equipment and building materials with a surface temperature below its dew point, the water will condense onto the cooler surface. The condensation can damage finishes and, in the case of laboratories, surgeries, and process plants like clean rooms, the condensation can ruin materials and products.

It is important to assess how susceptible the system is to problems with introducing 100% outside air during extreme weather. At a minimum, these issues should be discussed with the Owner and the design team to understand how they anticipated dealing with these occurrences. Document the procedures in the project’s operating manuals and commissioning reports. These issues can also impact how long the functional testing will take and what preparatory steps need to be taken to allow the testing to proceed without endangering the equipment or building materials and finishes.

Even if the owner is willing to accept the risk of damage due to a false trip of the system, there are still issues to deal with if the commissioning and acceptance phases of the project occur during extreme weather. In most instances, troubleshooting problems with the system will require sustained operation in the smoke control cycle for much longer than would be required for a certification test. If the schedule cannot be adjusted to allow the testing to be performed during moderate weather, it may be necessary to drain coils for the duration of the test process and/or only test for short intervals of time. These changes can significantly extend the test cycle and make troubleshooting more difficult.

Even if the preparatory testing can be performed prior to the acceptance test, if the acceptance test falls on a day when the weather is extreme, it will be necessary to take the appropriate precautions to protect the systems. It may be necessary to develop a contingency procedure that will allow the project team to quickly drain coils and take what ever other steps are necessary immediately before the demonstration to the code