Smoke Control for Dummies

The Basics of Smoke Control Made Simple

Do you struggle to understand smoke control for fire alarm systems? No need to stress out as you are not alone. Let's break it down so it is easier to digest.

Smoke control is a vital aspect of fire protection engineering that aims to prevent the spread of smoke and toxic gases in buildings during a fire. Smoke control systems use various strategies, such as mechanical ventilation, pressurization, and compartmentation, to limit the movement of smoke and protect the occupants and property from its harmful effects. In this blog post, you will learn about the principles, design, and applications of smoke control systems, as well as the relevant codes and standards that govern their performance. You will also find some useful resources and references to help you further explore this topic. Whether you are a fire protection engineer, a building owner, an installer, or a curious reader, this blog post will provide you with valuable insights into the science and practice of smoke control.

Fire alarm systems are essential for the activation and operation of smoke control systems. Fire alarm systems can detect the presence of fire and smoke, alert the occupants and the fire department, and initiate the appropriate smoke control actions. Fire alarm systems can also monitor the status and performance of smoke control systems and provide feedback and control signals to the building management system. Fire alarm systems should be listed, compatible and integrated with the smoke control systems to ensure coordinated and effective response to fire emergencies.

Smoke control systems are complex and require careful design, installation, and maintenance. Smoke control systems should be based on a thorough analysis of the fire hazards, the building characteristics, the occupant needs, and the fire department operations. This approach is referred to as a smoke control report or rational analysis and is required to be completed by a registered fire protection engineer (FPE) per the International Building Code 2021 Section 909.4. The rational analysis or smoke control report will cover which type of smoke control system will be employed (passive vs. mechanical), which smoke control method will be utilized (pressure, exhaust, or air flow), construction methods, sequence of operation and inspection and testing procedures. There are other items covered within the report such as but not limited to stack effect, temperature effect of fire, wind effect, climate and duration of operation. 

What Codes and Standards Dictate Smoke Control Systems?

Smoke control systems are required and regulated by codes and standards that specify the performance requirements, design criteria, installation methods, and testing procedures for different types of buildings and occupancies. Some of the codes and standards that address smoke control systems are as follows:

- 2021 International Building Code (IBC) Chapter 9: Fire Protection and Life Safety    Systems
- ASHRAE Handbook of Smoke Control Engineering
- NFPA 92: Standard for Smoke Control Systems
- NFPA 101: Life Safety Code
- NFPA 72: National Fire Alarm and Signaling Code

- Underwriters Laboratories, UUKL, Smoke Control Equipment (ANSI/864 units for     fire protective signaling systems)

Where are Smoke Control Systems Required per Code?

• Atriums (three stories or more) within covered malls - IBC 2021 Section 402.7.2.
• High-Rise Buildings - IBC 2021 Section 403.4.7.
• Atriums (three stories or more) - IBC 2021 Section 404.5.
• Underground Buildings - IBC 2021 Section 405.5.
• Mechanical Access Enclosed Parking Garage -IBC 2021 Section 406.6.4.2.
• Windowless Buildings Group I-3 - IBC 2021 Section 408.9
• Large Stages (Greater than 1,000sq' in Area or 50' in Height) - IBC 2021 Section 410.2.7.

Smoke Control Underground Structures

Smoke control systems can be classified into two main types: passive and mechanical.

Passive smoke control systems rely on the buoyancy and pressure differences of smoke and air to create ventilation openings that allow smoke to escape and fresh air to enter. Examples of natural smoke control systems are automatic opening vents (AOVs), atrium exhausts, opposed airflow, and smoke reservoirs.

• Openings are protected by automatic closing equipment or devices.
• Fire Dampers and Combination Fire Smoke Dampers
• Fire Rated Doors with Magnetic Hold Open Devices (Door Holders)
• Activation - Consult the Approved Rational Analysis / Smoke Control Report.
• Smoke Detectors / Heat Detectors located at fire rated doors and combination fire smoke dampers.
• Duct Smoke Detectors located at HVAC units for shutdown and combination fire smoke dampers. 
• Verification NOT required.
• Positive status of fan shutdown, door closure or damper activation is not required per IBC 2021 Section 909.12.1. Consult the rational analysis as it may supersede this code section. 
• Wiring
• In addition to the requirements of NFPA 70, all wiring regardless of voltage shall be fully enclosed within a continuous raceway.

Mechanical smoke control systems use fans, dampers, ducts, and other devices to create pressure differences and airflow patterns that control the direction and speed of smoke movement. Examples of mechanical smoke control systems are pressurization method, exhaust method, and air flow method systems.

• Pressurization Method - IBC 2021 Section 909.6. This approach utilizes pressure differences across smoke barriers to maintain a tenable environment zones adjacent to the smoke control zone of origin. 
• Per IBC 2021 section 909.6.1, the minimum pressure across the smoke barriers is 0.05" water gauge. 
• The maximum pressure differential is dependent upon the opening force of exit doors. Per IBC 2021 section 1010.1.3 #2, the door shall not require more than 30 pounds of force to set in motion and 15 pounds to fully open. 
• Required to have complete automatic control 2021 IBC section 909.12.3.1.
• In addition to the requirements of NFPA 70, all wiring regardless of voltage shall be fully enclosed within a continuous raceway.

Smoke Control Pressurization Method Detail

Smoke Control Stairwell Pressurization

• Exhaust Method - IBC 2021 Section 909.8. Where approved by the AHJ, the exhaust method may be utilized in large areas such as atriums or malls. Large smoke exhaust fans are utilized to evacuate smoke from the area. Makeup air (MAU) fans, automatic windows or doors may be used to replace air removed from the space by process of the smoke exhaust fan. When the smoke control exhaust method is utilized, the system must keep the smoke layer at least six feet above the highest level meant for egress within the smoke zone. Smoke Control Systems utilizing the exhaust method shall be designed in accordance with NFPA 92.
• Required to have complete automatic control 2021 IBC section 909.12.3.1.
• In addition to the requirements of NFPA 70, all wiring regardless of voltage shall be fully enclosed within a continuous raceway.

Smoke Control Exhaust Method Detail

Smoke Control Exhaust Method Atrium

• Air Flow Method - IBC 2021 Section 909.7. Where approved by the AHJ, the air low method is used for facilities with smoke migration through openings that are in the permanently open position. Airflow shall be directed to limit smoke migration from the zone. Airflow shall not exceed 200 feet per minute. Smoke Control Systems utilizing the air flow method shall be designed in accordance with NFPA 92.
• This method shall not be employed where either the quantity of air or the velocity of the airflow will adversely affect other portions of the smoke control system, intensify the fire, disrupt smoke plume dynamics or interfere with exiting. Airflow towards the fire shall not exceed 200 feet per minute. Where the calculated airflow exceeds this limit, the airflow method shall NOT be used. 909.7.1.
• Required to have complete automatic control 2021 IBC section 909.12.3.1.
• In addition to the requirements of NFPA 70, all wiring regardless of voltage shall be fully enclosed within a continuous raceway.

Smoke Control Airflow Method Detail

Duration of Operation

2021 IBC Section 909.4.6 states that all portions of active or engineered smoke control systems shall be capable of continued operation after detection of the fire event for a period of not less than either 20 minutes or 1.5 times the calculated egress time, whichever is greater. 

What is Verification or Positive Status?

Smoke control equipment utilized in a mechanical smoke control system will be required to comply with IBC 2021 Section 909.12.1 "Verification". This is also known as positive status. This is the process of utilizing fire alarm monitoring modules to supervise the activation of fans, dampers and doors in a smoke control event. The fire alarm monitor modules can be connected to variable frequency drives (VFDs), end switches, pressure differential switches, and current switches. These components provide contact closure to trip the associated fire alarm monitoring module to prove the fan, damper, or doors activated as intended per the approved rational analysis or smoke control port.  

Smoke Control Positive Status Equipment

Examples of how positive status for smoke control system can be wired to a fire alarm monitoring module. In these examples, a Notifier FDM-1 addressable dual monitor module is used to show how to wire up a damper actuator end switch for normally open and normally closed conditions. 

Fire Smoke Damper Status Monitoring Open Detail

Fire Smoke Damper Status Monitoring Open Detail

There is more to smoke control verification.

Another requirement for verification is a preprogrammed weekly self test sequence that shall report abnormal conditions audibly, visually, and by printed report. The pre-programmed weekly test shall operate ALL devices equipment and components used for the smoke control system.

Exception:

• Where verification of individual components tested through the preprogrammed weekly testing sequence will interfere with, and produce unwanted effects to, normal building operation, such individual components are permitted to be bypassed from the preprogrammed weekly testing, when approved by the AHJ and in accordance with BOTH of the following:

1. Where the operation of components is bypassed from the preprogrammed weekly test, presence of power downstream of all disconnects shall be verified weakly by a listed control unit.
2. Testing of all components bypassed from the preprogrammed weekly test shall be in accordance with section 909.20.6 of the International Fire Code IFC.

Example of a UL Listed Smoke Control Printer for Weekly Testing Reports

Fire Fighter's Smoke Control Panel

A fire fighter's smoke control panel for first responder purposes ONLY shall be provided and include manual control or override of automatic control for mechanical smoke control systems. If the facility is a high-rise structure or equipped with smoke protected assembly seating, the fire fighter's smoke control panel shall be installed with the fire command center (FCC). For all other buildings that may require a smoke control system, the fire fighter's smoke control panel shall be installed in an area approved by the AHJ adjacent to the fire alarm control panel. 2021 IBC Section 909.16.

Smoke Control Indication LEDs

All fans, dampers and other operating equipment shall be depicted on the fire fighter's smoke control panel along with clear indication of the airflow. Status indicators shall be included for all smoke control equipment annunciated by fan, damper and or zone. 2021 IBC Section 909.16.1.

1. Fans, Dampers and Other Operating Equipment NORMAL status = WHITE
2. Fans, Dampers and Other Operating Equipment OFF or CLOSED status = RED
3. Fans, Dampers and Other Operating Equipment ON or OPEN status = GREEN
4. Fans, Dampers and Other Operating Equipment FAULT status = AMBER/YELLOW

Smoke Control Switches

The following switches shall be provided on the smoke control panel to provide control capability over the complete smoke control equipment with the building: 2021 IBC Section 909.16.2

• ON-AUTO-OFF control over each individual piece of operating smoke control equipment that can be controlled from other sources within the building. This can include: stair pressure fans, smoke exhaust fans, supply fans, return fans, exhaust fans, elevator shaft fans, and other operating equipment used or intended for smoke control purposes. 

Smoke Control On-Auto-Off FAN Switch

• ON-AUTO-OFF control over individual dampers relating to smoke control and that are controlled from other sources within the building.

Smoke Control On-Auto-Off DAMPER Switch

• ON-OFF or OPEN-CLOSED control over smoke control and other critical equipment associated with a fire or smoke emergency and that can only be controlled from the fire fighters smoke control panel. 

Smoke Control On-Off DOOR Switch

Exceptions:

1. For complex systems (where approved), controls and indicators can be combined to control and indicate all components of a single smoke zone as a single unit. This allows for one switch to control multiple doors, dampers or fans within a single smoke zone. Example: Five dampers on the 10th floor that are all required to close upon smoke mode activation could be controlled and indicated on a single switch with LEDs on the 10th floor of the fire fighter's smoke control panel. 2021 IBC Section 909.16.2

The ON-OFF and OPEN-CLOSE switches shall have the highest priority over any control point within the building. Once automatic or manual control has been initiated from the fire fighter's smoke control panel, any other point in the building shall NOT contradict the control action. The only exception is power disconnects required by NFPA 70 is the only exception.

The AUTO position on three-position switches shall allow automatic or manual control action from other control points within the building. The AUTO position is the normal nonemergency position. 

Fire Fighter's Smoke Control Example

Fire Fighter's Smoke Control Panel

Smoke Control System Response Time

Per 2021 IBC section 909.17, upon receipt of an alarm condition at the fire alarm control panel fans, dampers, and automatic doors shall have achieved their proper operating state and the final status shall be indicated at the smoke control panel within 90 seconds. 

Power Requirements

• Standby Power Requirements per section 2702.2.17 of the 2021 IBC states that standby power shall be required for smoke control systems per sections 404.7, 909.20.7.2, and 909.21.5.
• Per section 909.12.1 the smoke control system shall monitor for the presence of power downstream of all disconnects. This will require a monitor module as well as an isolation relay (PR-1 or MR-101) at each power source. Make sure to pay attention to DAMPERS. A lot of the systems today will have a light switch adjacent to the damper actuator for the purpose of dropping power to the unit for service. If this is the case, you will need a monitor module and relay at each of these locations. Pay attention to this when bidding a project as this could potential add quite a few more modules than you may have accounted for.

How are smoke control systems commissioned and tested? 

Per the 2021 International Building Code Section 909.3, smoke control systems shall undergo special inspections and testing in place to verify the proper commissioning of the smoke control design in its final installed condition. As noted above, the rational analysis or smoke control report is required to include procedures that shall be used during the testing and commissioning process. 

• Per the 2021 IBC, Section 1705.19, Smoke Control Systems shall be tested by a special inspector. 
• As defined by the 2021 IBC Definitions, a special inspector is a qualified person employed or retained by an approved agency and approved by the building official as having the competence necessary to inspect a particular type of construction requiring special inspection. 
• Per the 2021 IBC, Section 1705.19.1, the Smoke Control Testing Procedure shall include:
1. During erection of ductwork and prior to concealment for the purpose of leakage testing and recording of device and equipment locations. This includes but not limited to fans, dampers, smoke detectors, waterflow switches, and verification equipment as outlined above.
2. Prior to occupancy and after sufficient completion for the purpose of pressure differential testing, air flow measurements and detection and control verification. 
• Per 2021 IBC, Section 1705.19.2, approved agencies for smoke control testing shall have expertise in fire protection engineering, mechanical engineering, and certification in air balancing. 

Reports

• Per 2021 IBC Section 909.18.8.3, A complete report of testing shall be prepared by the approved agency. The report shall include identification of all devices by manufacturer, nameplate data, design values, measured values, and identification tags. Your hope shall be reviewed by the responsible registered design professional and, when satisfied that the design intent has been achieved the responsible registered design professional shall sign seal and date the reporter.
• A copy of the final report shall be given to the fire code official along with an identical copy to be filed in an approved location at the facility. 2021 IBC 909.18.3.1.
• Charts drawings and other documents identifying and locating each component of the small control system as well as describing its proper function and maintenance requirements shall be maintained on file at the building and accompany the report required by section 909.18.8.3. Devices shall have an approved identifying tag on them consistent with the other required documentation and shall be dated indicating the last time they were successfully tested and by whom.

System Acceptance

• 2021 IBC Section 909.19 states, buildings that are required by this code to employ a smoke control system shall not be issued a certificate of occupancy until such time that the AHJ determines the provisions of chapter 909 have been fully complied with and that the fire department has received ample instruction on the operation both automatic and manual operation of the smoke control system. In addition, a written maintenance program complying with the requirements of section 909.20.1 of the International Fire Code (IFC) has been submitted and approved by the AHJ.

Plan on at least three inspections to commission a smoke control system.

• Pre-Test the system. Just like a fire alarm system, the sequence and equipment must be ran through prior to calling out the AHJ. The pre-test shall be conducted once all of the power is present, doors are installed, and all fire alarm/smoke control components are in place and programmed per the rational analysis, sequence of operations and approved documentation. Verify all indicators on the fire fighter's smoke control panel as well as manual and automatic operation. 
• Test with the third-party fire protection firm. Please note this can be the same firm that performed the rational analysis pending they have sufficient training and expertise in testing and commissioning smoke control systems. Depending on the individual conducting the third-party test you may have different requirements. However, you should still run through everything you tested during the pre-test as well as the pre-programmed weekly self-test. At the end of this test, the third party testing firm will issue a report per section 909.18.8.3 and give it to the Fire Code Official. 
• Final inspection with the AHJ / Fire Code Official. Once the third-party testing firm has issued their report, the AHJ will want to run through a final test. It is up to the AHJ on what will be tested. In my experience, some AHJs will trust the third-party testing firm and perform minimal testing to satisfy their needs. However, some AHJs will want to run through a complete test of all components. Keep this in mind when bidding projects as these tests can take quite a while depending on their complexity. 

OSID by Xtralis - Your Beam Detector Replacement

What is a Beam Detector?

A beam detector is a fire alarm detection device that projects a beam of light across a large area to detect smoke.  These devices are typically installed in large areas where spot type smoke detection is not practical due to cost or location.

Do you prefer to install beam detectors?

Whether you have been in the fire alarm industry for a month or 30 years, you have more than likely had to deal with beam detectors.  Some salesmen and technicians shriek when they hear the term and others have some what of a love hate relationship with them.  The simple fact is beam detectors can be a pain to adjust and keep true,  however they save a lot of money on detectors, wire, conduit and labor.  The concept of being able to cover a large open area with one detector is great and has become the preferred method of protecting warehouses, airports, gymnasiums, atriums and more. 

When I first got into the industry we were using Hochiki beam detectors which worked via a physical transmitter and receiver unit.  The main transmitter required re-settable power and IDC or SLC (if using an addressable module).  While this is not any different than the more modern System Sensor BEAM1224, the receiver required power as well as an additional pair of wires for communication between the two units.  These additional circuits where a burden, however the worst part was the adjustment.  Having to look through the tiny mirror to zero in the beam and then follow up with a coarse and fine tune got to be frustrating.  As mentioned above, the System Sensor BEAM1224 uses a similar technology that has been updated to eliminate the receiver unit.  The BEAM1224 uses reflectors to bounce the beam back into the transmitter.  Even though this upgrade eliminates the receiver, extra power and communication circuit, the adjustment can still be a nightmare to fine tune.  Lastly once you adjust the beams, there is always the possibility of building movement which can throw the adjustment out of whack and require a return trip.  With that in mind, remember that beam detectors are not typically installed in easy to reach locations.   

Xtralis has a response to this issue and it goes by the name OSID

Xtralis is more commonly known for their VESDA systems but have a few other products you may not be aware of.  The Open-Area Smoke Imaging Detection or OSID unit is one that you may what to start looking into.  This newer beam detection unit does not use a receiver or reflector like we have become accustomed to.  In fact the OSID uses an Imager and Emitter with a maximum coverage distance of up to 492 feet.  In simple to understand terms, the Imager (much like a camera) is simply looking for the emitter in its field of view.  If the Imager sees the Emitter, then you are good to go.  Unlike standard projected beam type detection, you are not relying on a beam that has to be precisely lined up to reflect back to its point of origin.  This new technology reduces alignment troubles and issues due to building movement.  Some other key points to mention include dual wavelength LED based smoke detection (UV and IR), high tolerance to false alarms and troubles, on-board event log, and the OSID is extremely easy to setup and get online.  Another important note is the Emitters come in both high and standard power as well as hard wired or battery powered.  The battery power option makes it easy when replacing a System Sensor BEAM1224 unit with reflectors. 

What makes up the OSID beam detection system?

The OSID Imagers come in two different versions.  

• The OSI-10 which has a 8 degree field of view and can be linked to 1 Emitter.  This Imager has a coverage distance of 30-150 m.
• Note this Imager is NOT suitable for use with the High Power Emitters (OSE-HPW and OSE-HP-01).  See below.
• The OSI-90 which has a 80 degree field of view and can be linked to up to 7 Emitters.
• When using the OSE-SP-01/W the coverage distance is 6 - 34 m
• When using the OSE-HPW the coverage distance is 12 - 68 m
• When using the OSE-HP-01 the coverage distance is 12  50 m

The OSID Emitters come in four different versions.

• The OSE-SPW is a a standard power Emitter that requires a hard-wired 24 VDC power source
• The OSE-SP-01 is a standard power Emitter that is powered via an alkaline battery with a guaranteed 5 year life span.
• The OSE-HPW is a high power Emitter that requires a hard-wired 24 VDC power source.
• Not suitable for use with the OSI-10 Imager.
• The OSE-HP-01 is a high power Emitter that is powered via an alkaline battery with a guaranteed 3 year life span.
• Not suitable or use with the OSI-10 Imager.

Setup and Alignment of the OSID - YES, it's that Easy!

Whether you are installing the OSID in a new facility or replacing your existing beam detectors, the setup is simple!  The first step would be configuration.  Are you planning on covering an area where one beam is sufficient or are you looking at an atrium with multiple levels to protect.  As noted above, the OSI-10 has an 8 degree field of view and can link with only 1 emitter.  This is good for your standard beam application like gyms, warehouses or the peak of an atrium.  Remember only one emitter can be used with each OSI-10 but multiple OSI-10s can be installed on your system.  Important note, do not use the high powered emitters with the OSI-10.

Now let's say you have a theater or atrium with multiple levels requiring detection.  In this case you may want to eliminate multiple OSI-10 imagers and go with the OSI-90.  This imager has an 80 degree field of view and can connect up to 7 emitters.  This setup will allow the installer to use one OSI-90 in the corner of the room while placing the emitters at the opposite end of the space at different heights to capture the area to be protected.  The use of 3 emitters will cover 6,000 sq' while 5 emitters will cover 20,000 sq'.

OSID Mounting

The Imager an emitters are same footprint and both come with an easy to install mounting bracket.  The bracket has multiple mounting slots making it easy to affix to existing boxes, new boxes or walls.  Once the bracket is firmly installed on the wall, the OSID imager and emitter simply slide onto 3 protruding areas on the bracket.  The housing has 4 knockouts located at the top and back towards the left hand side of the unit giving you access to the wiring terminals.  Terminals include: alarm contacts, fault contacts, rest switch, power in, power out, Fire LED and heater.  The Imager has plenty of space to internally mount a mini addressable module.  Once your wiring is complete, you are going to want to hold off on powering up or activating the unit.  To the right of the board, there is SW1 containing 10 dip switches.  These switches allow you to configure the amount of emitters, latching or non-latching and dust rejection.  make sure you set these prior to power up. 

OSID Alignment

Once you have your OSID imager and emitters securely wired and mounted, you are going to want to start the initial alignment process.  Now this is where OSID pulls away from the competition!  Xtralis makes a laser alignment tool (part # OSP-002) that can be purchased separately or purchased along with the Installation and Maintenance Kit.  I recommend picking up a kit or two with your first purchase.  The kit includes large reflectors to assist with laser alignment, a red plastic test panel, the laser alignment tool, diagnostic software cable and instructions.  Note the software can be downloaded for free from the manufacturers website.

Important!  You are going to want to start with the emitters when aligning.

Once you get to the unit, you will notice the very flexible ball and socket design.  This allows the lens to aim at a large variety of angles.  Located at the end of the laser alignment tool, you will notice a hex wrench.  Simply insert that hex head into the small hole just below the lens.  After you insert the tool, turn on the laser and move the lens around until the laser beam is within approximately 2 feet of the imager.  Note that in brightly lit areas, it may be necessary to have an assistant hold up the reflective film at the imager.  This will make the laser more noticeable.  Once the laser beam is on target, simply turn the tool clockwise 90 degrees to lock the ball and socket assembly as well as activate the unit.  Once activated, the lens will pulse with a blue light that can only be seen in line of sight.

Align the Imager after the Emitter(s)

Once you have all the applicable emitters lined up to the imager, you can do the same process in reverse.  Use the same steps as above to line the imager up to the emitter.  After you have the laser lined up, turn the tool 90 degrees clockwise to lock it in place and activate with Xtralis refers to as "Training Mode".  When in training mode, the Imager is looking for all emitters and calibrating itself.  This process can take up to 10 minutes.  During the process, the amber LED will flash.  After training mode is complete the Green LED will flash at intervals of approximately 10 seconds.

Once all these steps have been successfully completed, the fault contacts should clear and your system will return to normal.  Testing is as simple as your standard beam detector and as noted above, the Installation and Maintenance Kit comes with a red testing screen that is rigid enough to last for a long time.  If you are interested, Xtralis provides free diagnostic software on their website for use in reading event logs and narrowing down issues with the unit.  However there is no need to use this software in the setup of the OSID.

In closing the OSID is a high quality replacement to the dreaded beam detection we have been forced to use throughout our careers.  We highly recommend you purchase one of these setups and install it on your next project.  The small increase in price is welcomed on the back-end with easier installation, alignment and setup.  This is a product you can expect to quickly take open spaces by storm.               

Smoke Detectors for HVAC Shutdown

"For fire smoke dampers, should I use an in-duct spot type smoke detector or a duct detector?"

Sampling tube style duct detectors are listed for a minimum air velocity of 100 fpm (feet per minute). If you are to ensure the rating of the wall at duct penetrations (dampers), you must provide coverage per The International Building Code IBC 2021 Edition Section 717.3.3.2.  

717.3.3.2 Smoke damper actuation. The smoke fire damper shall close upon actuation of a listed smoke detector or detectors installed in accordance with Section 907.3 and one of the following methods, as applicable:

1. Where a smoke damper is installed within a duct, a smoke detector shall be installed in the duct within 5 feet (1524 mm) of the damper with no air outlets or inlets between the detector and the damper. The detector shall be listed for the air velocity, temperature and humidity anticipated at the point where it is installed. Other than in mechanical smoke control systems, dampers shall be closed upon fan shutdown where local smoke detectors require a minimum velocity to operate.

2. Where a smoke damper is installed above smoke barrier doors in a smoke barrier, a spot-type detector listed for releasing service shall be installed on either side of the smoke barrier door opening.

3. Where a smoke damper is installed within an air transfer opening in a wall, a spot-type detector listed for releasing service shall be installed within 5 feet (1524 mm) horizontally of the damper.

4. Where a smoke damper is installed in a corridor wall or ceiling, the damper shall be permitted to be controlled by a smoke detection system installed in the corridor.

5. Where a total-coverage smoke detector system is provided within areas served by a heating, ventilation and air-conditioning (HVAC) system, smoke dampers shall be permitted to be controlled by the smoke detection system.

The 1st method above states that you must provide a smoke detector installed in the duct within 5’ of the fire smoke damper, and that the smoke detector shall be listed for the air velocity.  If you shut down the fan, there will not be a minimum air velocity of 100 fpm to achieve the proper listing of a sampling tube style duct detector (System Sensor D4120 for example).  Notice that this same paragraph states that “Other than in mechanical smoke control systems, dampers shall be closed upon fan shutdown where local smoke detectors require a minimum velocity to operate”.

What if we decide to use sample tube duct smoke detectors?

If we are using duct detectors for damper control, then whenever the fan is off, the dampers must be shut since the duct detectors such as the System Sensor D4120 require a minimum velocity of 100 fpm to operate.  Does this mean we then have to monitor fan status, and shut dampers upon fan shutoff, or shall the mechanical contractor have to inter-tie with all the dampers associated with that fan?  If we decide to monitor the fan, that creates another issue—per the IMC (International Mechanical Code), if a damper has automatically been activated to close, the associated fan must be shutdown.  Picture this scenario—AHU1 turns off, so we shut down the dampers.  The damper circuit we are controlling also serves dampers associated with AHU2, therefore we must shut that one down as well.  Since AHU2 is serving other areas of the building, we must shut those circuits of dampers as well, and so on until the whole building has typically been shut down for HVAC equipment including dampers.

What if we use spot type In-Duct Smoke Detectors?

On the other hand, if we are protecting the fire smoke dampers with an in-duct detector, you can have the fan shut down upon duct detector for the fan, and the dampers throughout the rest of the building may remain open and the other fans may remain on.  The damper is still protected with the in-duct smoke detector to ensure the rating of the wall to shut the damper upon detection of smoke, and if the in-duct smoke detector activates, then we go through the shut-down process of the fans and dampers throughout the building as exampled above.  Note that in-duct detectors have a listed minimum air velocity of 0 fpm, meaning that it does not “require a minimum velocity to operate“, therefore not requiring shutdown of the building upon a single fan being shut down.

Building owners really don’t like when their building heats up because they are servicing one of their fans, or one of the many fans in their building turns off due to a number of circumstances that are not necessarily indicative of a fire, and our fire alarm system shuts down all HVAC movement in the building.  Mechanical contractors don’t like it when they are forced to interface with individual dampers to close upon fan shutdown.  And finally, electrical/mechanical contractors really don’t like it when we force them to give us a true status of the fan via a Current or Differential Pressure switch when the fan is not a part of a smoke control system and it was not shown on their drawings or bid docs.

If you like what you see here then make sure to join our Facebook Group here.

Fire Damper vs. Fire Smoke Damper

Do you know the difference between fire dampers and fire smoke dampers?

This is a questions that seems to come up a lot in the fire alarm install and design world.  The definition of a damper is "A person or thing that damps or depresses".  In other words it is a plate that is placed within the duct work of an HVAC system to regulate or in some cases stop air flow.

Now in the fire alarm industry we are more concerned with the terms "Fire Damper", "Smoke Damper" or "Combination Smoke Fire Damper".  Whats is the difference?  Well it is actually quite simple as we explain below.

• A "Fire Damper" as defined in the CMC (California Mechanical Code) 2022 Edition Section 206.0 - "An automatic-closing metal assembly of one or more louvers, blades, slats or vanes that close upon detection of heat so as to restrict the passage of flame and is listed to the applicable recognized standard."  The automatic means can be accomplished one of two ways: 1) by a fusible link that will melt upon heat thus releasing the louvers into the closed position.  2)  by motorized actuators that will close upon loss or gain of power.  These are typically controlled by and addressable relay module.

• A "Smoke Damper" as defined in the CMC (California Mechanical Code) 2022 Edition Section 206.0 - "A damper arranged to seal off airflow automatically through a part of an air duct system so as to restrict the passage of smoke and is listed to the applicable recognized standard."

• A "Combination Fire Smoke Damper" is exactly that, a combination of a "Fire Damper" and a "Smoke Damper".

When are they required and how do I know when to use what type?

Keep in mind that the fire alarm contractor will not be providing or installing these.  However, it is nice to know what to look for on a bid set of plans or during a job walk.  First up is the "Fire Damper".  A fire damper is installed in HVAC duct work at the intersection of a rated barrier such as walls or partitions.  The damper is in place to secure the integrity of the rated barrier in the event of heat or flames around 165 degrees F.  Like we stated above, the fusible link will melt thus releasing the louvers on the damper.  Once the louvers are closed or shut, the fire barrier is now secured from allowing flames to penetrate prior to the rating level of the barrier itself.

Smoke dampers are similar however, they close in the presence of smoke.  Now since the smoke damper cannot obviously sense smoke, we need to install a smoke detector. The smoke detector can either be a system smoke (tied to a building fire alarm system) or a stand alone smoke solely in place to activate the smoke damper.  Smoke Dampers are required to be installed on walls that separate smoke barriers.  

What's a smoke barrier you ask......  A smoke barrier is a continuous surface such as a wall, floor, or ceiling constructed to restrict the movement of smoke.  A smoke barrier can be either vertical or horizontal. 

Now a "combination smoke fire damper" is located in a situation where both fire rating and smoke barriers come into play.  A combination fire smoke damper also needs a smoke detector just like the smoke damper.  The smoke detector can either be a duct smoke detector (System Sensor D4120 or DNR) or a pendant mounted detector within the duct work itself.  Once the detector senses smoke particles it will either through programming or local relay base close the damper louvers.

UUKL Smoke Control For Fire Alarms

UL (Underwriters Laboratories) has a section titled 864.  ANSI/UL-864 is the section that covers "Standards for Control Units and Accessories for Fire Alarms".  ANSI/UL 864 is currently on its 9th revision.  Published on September 30, 2003 with a current effective date of December 31, 2008, the new edition incorporates approximately 300 changes, including 100 pages of new requirements from the previous edition.


With that said, UUKL is a separate listing category under UL 864.  Control devices used in smoke control systems have a UUKL listing.  UL's UUKL listing is a category under UL 864, Control Units and Accessories for Fire Alarm Systems.  UUKL is for products covered under the description "Smoke Control Equipment."  Equipment that receives UL's UUKL rating has been tested for integrity and long term reliability.  The equipment is subjected to extreme temperatures, humidity  and electrical transients and surges. This testing ensures that the devices will continuously perform even under severe and abnormal conditions.

A UUKL Smoke Control System is a combination of fan, dampers, warning devices, relays and modules that all work together to perform the containment function of any smoke event at any location in a building.  If the UUKL Smoke Control System is design correctly it should inhibit and or prevent the movement of smoke into areas leading to exits or other areas designated safe zones in a building.

Read more about UUKL Smoke Control Panels HERE.


make sure to join our Facebook Group for great discussions HERE!!!!