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. 

Duct Smoke Detectors for Supply vs Return - CALIFORNIA

Does California require Duct Smoke Detectors on the Return Side?

Since this question comes up so often, I felt it would be beneficial to put an article together with the answers and applicable code/standard references. Please note that the below information is pertinent to CA and may be altered by individual jurisdictions if they have formally adopted a local ordinance to supersede the state level requirements.

 There are two items to cover with this topic:

1. In California, are we required to install the duct smoke detector on the supply or return side of HVAC units GREATER than 2,000 cfm?
2. In California, are we required to install a duct smoke detector on both the supply and return side of and HVAC unit GREATER than 15,000 cfm? 

Before we can answer these questions, we need to know what codes and standards California has adopted. 

Chapter 35 of the California Building Code 2022 edition is dedicated to clarifying which codes and standards are adopted by the State Fire Marshal. The code/standard references are on the left with vertical columns signifying which agencies have adopted them. The third column from the left with the “Xs” is for the State Fire Marshal. From here we can tell that based on the 2022 CBC, the applicable standard for Fire Alarm is the 2022 edition of NFPA 72. Please also note that the IMC or International Mechanical Code is not found within this document.  This lets us know this code not valid in California and therefore its individual language does not apply.

2022 CBC MATRIX ADOPTION TABLE - CHAPTER 35

Duct Smoke Detectors based on NPFA 72 2022 Edition

NFPA 72 2022 Section 17.7.5.3.1 States “To prevent the recirculation of dangerous quantities of smoke, a detector approved for air duct use shall be installed on the supply side of air handing systems as required by NFPA 90A and 17.7.5.4.2.1”

Duct Smoke Detectors based on NFPA 90A

 Since NFPA 90A is referenced in the above NFPA 72 standard, it shall apply. The language for this standard is found in section 6.4.2.1 and reads as follows:

 “Smoke detectors listed for use in air distribution systems shall be located as follows:

1. Downstream of the air filters and ahead of any ranch connections in air supply systems having a capacity greater than 2000 cfm.
2. At each story prior to the connection to a common return and prior to any recirculation or fresh air inlet connection in air return systems having a capacity greater than 15,000 cfm and serving more than one story.”

Duct Smoke Detectors based on the International Mechanical Code (IMC)

NO Duct Smoke Detector on Return for units greater than 2,000 cfm in California

 The code that requires a duct smoke detector in the return side of a unit greater than 2,000 cfm is the International Mechanical Code. Keep in mind since this code is not a referenced standard in the California Building Code, it does not apply.

 Section 606.2.1 of the International Mechanical Code states a duct smoke detector shall be installed in return air systems with a deign capacity greater than 2,000 cfm.

Summary 

• NFPA 72 2022 17.7.5.3.1 - In California we are required to provide a duct smoke detector on the SUPPLY side of HVAC units per NFPA 90A.
• NFPA 90A 6.4.2.1 - In California we are required to provide a duct smoke detector on the SUPPLY side of HVAC units greater than 2,000 cfm
• NFPA 90A 6.4.2.1 – In California we are required to provide a duct smoke detector on each return inlet prior to a common return for HVAC units greater than 15,000 which serve more than one floor (below is a simple diagram showing this setup.)
• IMC 2021 606.2.1 – Requires a duct smoke detector in the return of HVAC units greater than 2,000 cfm. THIS DOES NOT APPLY IN CALIFORNIA

520 Hz Low Frequency for 120VAC Smoke Alarms IFC 2021

How is the new 2021 International Fire Code going to impact your fire alarm design and costs for Group R-1 and R-2 occupancies?

If you install fire alarm system in the residential vertical market, you need to keep reading.

When designing and pricing a new fire alarm system for group R-1 (hotels and motels) and R-2 (apartments, townhomes, and condos) you need to factor in 520Hz low frequency sounders for sleeping rooms. this is found in the 2021 International Fire Code (IFC) and 2022 NFPA 72 standard as follows:

2021 IFC Section 907.4.2.1.3
Audible signal frequency in Group R-1 and R-2 occupancies shall be in accordance with Sections 907.5.2.1.3.1 and 907.5.2.1.3.2

2021 IFC Section 907.5.2.1.3.1
In sleeping rooms of Group R-1 and R-2 occupancies, the audible alarm activated by the fire alarm system shall be 520-Hz low frequency signal complying with NFPA 72. 

2022 NFPA 72 Section 18.4.6.3*
Audible appliances provided for the sleeping areas to awaken occupants shall produce a low frequency alarm signal that complies with the following:

(1) The waveform shall have a fundamental frequency of 520 Hz +/- 10 percent.
(2) The notification equipment shall be listed for producing the low frequency waveform.

What does NFPA 72 consider a sleeping area?

To answer this question, you need to consult NFPA 72 2022 Annex A.18.4.6.3.

"The intent of this section is to require the use of the low frequency signal in areas intended for sleeping and in areas that might reasonably be used for sleeping. For example this section requires a low frequency audible signal in a bedroom of an apartment and also in the living room area of an apartment as it might have sleeping occupants. However, it would not be required to use low frequency signal in the hallways, lobby, an other tenantless spaces. In hotels, the quest rooms would require audible signals could use any listed audible appliances regardless of the frequency content of the signal being produced. This chapter of the code addresses notification appliances connected to and controlled by a fire alarm or emergency communications system. This chapter does not address dwelling unit protection such as smoke alarms and their audible signal characteristics. Requirements for single and multiple station alarms and household fire alarm systems can be found in chapter 29.  

To sum this up, NFPA 72 considers sleeping areas as bedrooms and living rooms.

Up to point, nothing has changed in the way we design and price new fire alarm systems in group R-1 occupancies and group R-2 occupancies. With that being said, lets get to the important code change noted above.

Here is where we get to the update!

2021 International Fire Code (IFC) Section 907.5.2.1.3.2

In sleeping rooms of Group R-1 and R-2 occupancies that are required by Section 907.2.8 or 907.2.9 to have a fire alarm system, the audible alarm signal activated by single or multiple-station smoke alarms in the dwelling unit or sleeping units shall be a 520-Hz signal complying with NFPA 72.

Where a sleeping room smoke alarm is unable to produce a 520-Hz signal, the 520-Hz alarm signal shall be provided by a listed notification appliance or a smoke detector with an integral 520-Hz sounder.

Here is the kicker. There are NO listed 120 VAC single or multiple station smoke alarms on the market with an integral 520 Hz sounder.

We all knew this was coming and surprise, here it is! If we simply the above code language, it states that the 120 VAC single and multiple station smoke alarms of group R-1 and Group R-2 occupancies must now produce a 520 Hz low frequency audible tone. 

___________________________________________________________________________________

Based on the second paragraph of Section 907.5.2.1.3.2, there are two ways to tackle this new requirement:

___________________________________________________________________________________

(1) Use a listed 520 Hz low frequency notification appliance

If this option is selected, you can utilize the wall or ceiling mounted 520 Hz low frequency notification appliances required by the 2021 IFC section 907.5.2.1.3.1 for occupant notification in group R-1 and and Group R-2 occupancies. These should already be captured by your minimum code design. However, with a standard design in mind, these appliances will only activate via a general alarm signal. This new 2021 code section 907.5.2.1.3.2 is requiring the single and multiple smoke alarms to sound these low frequency appliances. To accomplish this an addressable monitor module could be connected to a contact on the residential unit smoke alarms. This has been done for quite some time in Group R-2 occupancies used for university dorms or specific design criteria such a Marriott's Module 14.  In these cases, the addressable monitor module is in lace to supervise the in room smoke alarms. If these alarms activate, the fire alarm control unit (FACU) would receive a non-latching supervisory alarm without the activation of any occupant notification appliances. To insure the low frequency notification appliances activate via general alarm in addition to in-unit smoke alarm activation,  you would need an addressable control module to isolate each residential units notification appliance circuit (NAC). This way the system can be programmed to activate the in-unit NAC control module upon general alarm (corridor, smoke detectors, elevator lobby smoke detectorss, manual pull stations, waterflow, etc.) or the addressable monitor module connected to the 120 VAC single and multiple station smoke alarms. Remember to program the control module for latching upon general alarm activation and non-latching for the in-unit residential single and multiple station smoke alarms. 

Another scenario that will come up with this approach is audible tones synchroning as well as conflicting tones. If this method is used, an activated smoke alarm would sound it's internal sounder as well as the in room 520 Hz low frequency sounders. This would produce both the standard 3 KHz and 520 Hz tones in the space. Not sure if it is possible to disable the local piezo or sounder on a 120 VAC smoke alarm as this would rectify the conflicting tone issue. To top this off the new 2022 NFPA 72 standard requires audible tones to be synchronized. See section 18.4.3.3. We feel as though this could definitely produce an issue as the audible tones are produced from two different sources. Synchronizing the audible tones may be difficult or impossible.  

Key takeaways for option number one:

• Requires at least one addressable monitor module for each residential unit.
• Requires one addressable control module for each residential unit
• Requires a signaling line circuit (SLC) ran to each residential unit monitor module and control module.
• Requires a 24VDC power circuit to the addressable control module.
• Design the system so that each residential unit receives a separate isolated notification appliance circuit (NAC) fed from the control module noted above. 
• Confirm the electrical contractor is providing 120VAC single and multiple smoke alarms with dry contacts for the the capability to trip the addressable monitor module noted above. 
• Possible need for additional power supplies and signaling line circuit (SLC) cards depending on the base system.
• Ensure the audible tones from the single and multiple stations smoke alarm internal piezo and the fire alarm system low frequency Sounders are synchronized. Per 2022 NFPA 72 section 18.4.3.3
• Look into the issue of conflicting audible tones. As stated above there may be a method to disable the local piezo or sounder on the single or multiple stations smoke alarms. 

___________________________________________________________________________________

(1) Use an addressable system smoke detector with an integral 520 Hz low frequency sounder base.

If this option is selected for your design, you can replace the standard ceiling or wall mounted 520 Hz low frequency notification appliances with a low frequency sounder base connected to an addressable system smoke detector. As noted above per 2022 NFPA 72 Section A.18.4.6.3, these smoke detectors and 520 Hz low frequency sounder bases will be required in all sleeping areas which are considered bedrooms and living rooms. Like any other sounder base installation, make sure to account for the addition of a signaling line circuit (SLC) and sounder base notification appliance circuit. With this option, the electrical contractor can remove all power wiring, back boxes and single or multiple smoke alarms from their bid and installation. 

Key takeaways for option number two:

• Requires at least one addressable smoke detector with integral low frequency sounder base in each bedroom and Livingroom.
• Requires a signaling line circuit (SLC) ran to each residential unit smoke detector.
• Requires a 24VDC power circuit or notification appliance circuit (NAC) to the integral low frequency sounder base.
• Depending on your fire alarm system, you may need end of line power supervision modules to supervise the loss of sounder base power. 
• Confirm the electrical contractor is NOT providing 120VAC single and multiple smoke alarms, 120 VAC power circuits and back boxes as this will be covered in your fire alarm design. 
• Possible need for additional power supplies and signaling line circuit (SLC) cards depending on the base system.

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Author note: Make sure if option number two is selected for you redesign, you still incorporate the necessary 110CD or 177CD visual appliances in the ADA (Americans with Disabilities Act) units. 

This is a HUGE change to the code and we suggest you start the conversation with your architects, general contractors and electrical contractors so everyone is on the same page moving forward. 

Smoke Detector Spacing with Beams

Smoke Detector Spacing for Smooth Ceilings

Let's start with the basics of smoke detector spacing.  Based on 2022 NFPA 72, there is not a listed spacing for smoke detectors. Instead, you are instructed to consult with the smoke detector's published documentation.  However, NFPA 72 2022 edition section 17.7.4.2.3.1 states the following, "In the absence of specific performance based design criteria, one of the following requirements shall apply:

1. The distance between smoke detectors shall not exceed a nominal spacing of 30 feet and there shall be detectors within a distance of one-half the nominal spacing, measured at right angles from all walls or partitions extending upward to within the top 15 percent of the ceiling height.
2. All points on the ceiling shall have a detector within a distance equal to or less than 0.7 times the nominal 30 foot spacing.

What does this mean?

Number 1 above states you must have a smoke detector within one half the nominal spacing from walls.  One half of 30 feet is 15 feet.  In the image below you will see a total of six yellow circles each with a 30 foot diameter.  These circles represent the area covered by a spot type smoke detector based on a nominal spacing of 30 feet. As required by the 2022 NFPA 72, we have spaced each detector at 15 feet from walls and 30 feet apart.    

Smoke Detector Spacing with a Smooth Ceiling

What about the white areas not covered?

If you notice in the image, there are areas not covered by the yellow circles representing the smoke detector coverage.  This is where NFPA 72 2022 edition section 17.7.4.2.3.1 criteria number two comes into play.  

With a nominal spacing of 30 feet, you must insure that all areas of the ceiling have coverage within 0.7 times this 30 foot amount.  To find this distance, simply multiply 30 feet by 0.7 to get 21 feet.

If you use Pythagorean's Theorem you will come up with a surprising result.  Remember Pythagorean's Theorem is used to find the unknown side of a right triangle and is expressed as A squared + B squared = C squared.  In this case we have a right triangle in each quadrant of the yellow circles.  Each quadrant is 15 feet our and 15 feet up.  We can write this equations as:

15 squared + 15 squared = C squared 

225 + 225 = 450 squared

450 squared = 21.2132 feet

In the image below you will see a cleared depiction of how this all comes together. With this, it is clear that we have met the intent of the standard by mounting our smoke detectors 15 feet from the walls, 30 feet apart and still achieve 0.7 times the nominal spacing (21 feet) coverage at all points of the ceiling.

Smoke Detector Coverage for 30 Feet

NFPA and Smoke Detector Spacing Distances

The Annex of NFPA 72 provides us with a diagram to assist in smoke detector spacing. Note that smoke detectors are not listed for spacing.  Use the smoke detector's published installation documents and the spacing breakdown below to assist in your design.

For areas/corridors 10 feet wide, smoke detectors can be spaced at 41 feet.

For areas/corridors 15 feet wide, smoke detectors can be spaced at 39 feet.

For areas 20 feet wide, smoke detectors can be spaced at 37 feet.

For areas 25 feet wide, smoke detectors can be spaced at 34 feet.

For areas 30 feet wide, smoke detectors can be spaced at 30 feet.

Smoke Detector Spacing with Beam Construction

If your ceiling configuration involves beams, your smoke detector coverage can get a bit more tricky.

NFPA 72 2022 edition section 17.7.4.2.4.2 deals with level ceilings with beams. In a nutshell, this is how it breaks down:

• If the beam depth is LESS than 10% of the overall ceiling height, then smooth ceiling spacing for smoke detection can be applied.  Also note that in this scenario, you can choose to install the smoke detectors on the ceiling or the bottom of the beams. Reference the above text and images for smooth ceiling spacing.
• If the beams are are equal to or greater than 10% of the overall ceiling height, two scenarios are possible:
• If the beam depth is equal to or greater than 10% but less than 40%, use smooth ceiling spacing PARALLEL to the beams and one half spacing PERPENDICULAR to the beams.  With this scenario, the smoke detectors can be mounted on the ceiling or the bottom of the beams.
• If the beam depth is equal to or greater than 40%, a smoke detector shall be placed on the ceiling within each beam pocket.  Keep in mind that more than one smoke detector may be required to cover a given beam pocket.

How to Calculate Smoke Detector Spacing with Beam Construction 

Did you know the 2021 International Fire Code now requires 120 VAC single and multiple station smoke alarms to produce a 520 Hz low frequency audible tone? 

To calculate the beam depth for smoke detector spacing, convert your overall ceiling height into inches.  For example, if your ceiling is 12 feet it would convert to 144 inches.  Take 144 and multiply it by 0.1 to get 10%.  144" x 0.1 = 14.4".  In this case, ant beam depth of 14.4" or more would require an altered smoke detector lay out.  If you want an easier way to work this calculation and remember what spacing requirements go with the different percentages, we have you covered.  Download a FREE copy of our Excel Fire Alarm Calculation Tool and use the "SD BEAMS" tab.  All you need to do is input your ceiling height and beam depth in inches and the calculator will give you a color code for which spacing requirement is required (see image below).  Email us with any questions.   

Smoke Detector Spacing in Corridors with Beams 

What do you do if you have a corridor that is equal to or less than 15 feet in width with beams running perpendicular to the length of the corridor?  Consult NFPA 72 2022 section 17.7.4.2.4.2 (4).  This section of the standard allows you to use smooth ceiling spacing and the smoke detectors can be mounted on the ceiling, bottom of the beams or on the sidewall.

Smoke Detector Spacing in Rooms 900 Square Feet or Less

NFPA 72 2022 section 17.7.4.2.4.2 (5) allows the use of smooth ceiling spacing for smoke detection coverage in rooms that are equal to or less than 900 square feet.  You can also install the smoke detector on the ceiling or bottom of the beam. 

Smoke Detector above Fire Alarm Control Unit FACU

A question we see coming up more often is in regards to smoke detection above fire alarm control units.  The specific questions is, "Are you required to install a smoke detector above the fire alarm control unit (FACU) or fire alarm control panel (FACP)?".

Simply put the answer is YES and can be supported by the language found in NFPA 72 2022 edition section 10.4.5. (page #74).  This sections states the following:

"Unless otherwise permitted by 10.4.5.1 or 10.4.5.2, in areas that are not continuously occupied, early warning fire detection shall be provided at the location of each fire alarm control unit(s), notification appliances circuit power extenders, and supervising station transmission equipment to provide notification of fire at that location by one of the following means:

(1) An automatic smoke detector at the location of each control unit(s), notification appliance circuit power extender(s), and supervising station equipment.

(2) An automatic heat detector where ambient conditions prohibit installation of an automatic smoke detector."

Also note there is an Annex section related to this reference.  A.10.4.5 states that the equipment to be covered by this automatic smoke detection is a fire alarm control unit that is used to notify occupants and responders of a fire.

Here are a few other key items to keep in mind when dealing with this topic:

• The term Fire Alarm Control Unit (FACU) does NOT include annunciators or addressable devices.
• If the area where the FACU is located is continuously attended, a smoke detector is NOT required.  Keep in mind this is not intended for lobbies or offices where there are occupants coming and going throughout the day.  This is intended for areas such as lobbies with 24/7 security and security rooms where at least one guard is in attendance at ALL times.
• If the area where the FACU is located has full coverage smoke detection, then an additional smoke detector dedicated to the FACU is NOT required.
• If the single smoke detector intended to protect the FACU per 10.4.5 does not cover the entire space where the control equipment is located, then additional smoke detection is NOT required.

Now here is were it may become confusing for the designer or AHJ.  Section 10.4.5 as well as A.10.4.5 clearly state that the FACU to be protected is a control unit that is in place to notify occupants and first responders of a FIRE.  As you may or may not be aware, there are additional systems we deal with in this industry known as Dedicated Function Fire Alarm Systems.  

Building Fire Alarm System vs. Dedicated Function Fire Alarm System

As defined by NFPA 72 2022 edition Section 3.3.118 (page #29)

Building Fire Alarm System.  A protected premises fire alarm system that includes any of the features identified in section 23.3.3.1 and that serves the general fire alarm needs of a building or buildings and that provides fire department or occupant notification or both.

Dedicated Function Fire Alarm System.  A protected premises fire alarm system installed specifically to perform emergency control function(s) where a building fire alarm system is not required.  

Here is the code section that indicates when a Dedicated Function Fire Alarm Alarm Systems can be installed in place of a building fire alarm system per NFPA 72 2022 edition section 23.3.3.2.1. 

"In facilities without a building fire alarm system, a dedicated function fire alarm system shall be permitted and shall not be required to include other functions or features of a building fire alarm system."

The two most common dedicated function fire alarm systems typically used are:

• Dedicated function sprinkler monitoring system:  This is a system installed when a particular building does not require a building fire alarm system BUT still has an automatic fire sprinkler system employing more than 6 heads.  Example could be a small strip mall (Group M) with under 100  occupants but more than 6 automatic sprinkler heads.  Although this system is not in place to notify occupants or responders of a fire, a smoke detector is required above the panel since this system is in place to monitor the sprinkler system.  Per NFPA 72 2022 section 10.4.5 a smoke detector is required to protect "supervising station transmission equipment".

• Dedicated function elevator control system:  This is a system installed strictly and specifically to control the emergency functions of an elevator such as elevator recall and shunt trip.  These systems will typically have your elevator lobby/equipment room smoke detectors, heat detectors, relays and modules to perform the emergency control functions found in NFPA 72 2022 chapter 21.  Note this system would not be required to be monitored as it is not in place to monitor the status of an automatic sprinkler system.  In this case a smoke detector is NOT required above the control unit as it is not monitored nor is it in place to notify occupants or responders of a fire.

FACU Smoke Detector Installation Location

NFPA 72 2013 Smoke Detector Mounting Diagram

Pay attention to your applicable code as the installation location of this smoke detector changed
between NFPA 72 2010 and 2013 editions.

NFPA 72 2010 (A10.15 #1 and #2) state if the ceiling height is 15' or less, the smoke detector shall be installed on the ceiling or wall within 21' of the centerline of the FACU.  If the ceiling height exceeds 15', the smoke detector should be installed on the wall no more than 6' above the top of the FACU.

NFPA 72 2013 (A10.4.4) states the smoke detector shall be installed in accordance with section 17.7.3.2.1.  Section 17.7.3.2.1 states "Spot-type smoke detectors shall be located on the ceiling or, if on a sidewall, between the ceiling and 12 inches (300 mm) down from the ceiling to the top of the detector."

Carbon Monoxide Detector Mounting

Carbon monoxide alarms and detection systems now have more direction on mounting and alerting thanks to NFPA 72 2022

NFPA 720: Standard for the Installation of Carbon Monoxide (CO) Detection and Warning Equipment (2015) currently does not have any requirements for the mounting height/location of a carbon monoxide detector.  However, NFPA 720 does specify that is a carbon monoxide detector is installed in a room with a fire fueled appliance such as a generator, hot water heater, furnace, etc., it is to be mounted on the ceiling.

The reason behind the NFPA 720 placement of carbon monoxide detectors on the ceiling in these areas is makes perfect sense. Continue below:  

Carbon monoxide has a molar mass of 28.0, which makes it slightly lighter than air, whose average molar mass is 28.8. According to the ideal gas law, CO is therefore less dense than air.  With that said, the heat generated by these appliances will make the carbon monoxide (CO) more buoyant and present it to the carbon monoxide detector on the ceiling.

Another source for the mounting and installation of carbon monoxide detectors is found in NFPA 72 2019 section 17.12 "Carbon Monoxide Detectors"

NFPA 72 Carbon Monoxide Requirements per Chapter 17

NFPA 72 2022 Section 17.12.1 

Where required by other governing laws, codes, or standards, carbon monoxide defectors shall be installed in accordance with the following:

    1) On the ceiling in the same room as permanently installed fuel-burning appliances, and

    2) Centrally located on every habitable level and in every HVAC zone of the building, and

    3) Outside of each separate dwelling unit, guest rom, and guest suite sleeping area within 21 feet (6.4 m) of any door to a sleeping room, with the distance measured along the path of trave, and

    4) Other locations where required by appliance laws, codes, or standards or

    

NFPA 72 2022 Section 12.12.2 

Carbon monoxide detectors shall meet the following requirements:

    1) Carbon monoxide detectors shall be listed in accordance with applicable standards, such as ANSI/UL 2075, Gas and Vapor Detectors and Sensors.

    2) Carbon monoxide detectors shall be set to respond to the sensitivity limits specified in ANSI/UL 2034, Standard for Single and Multiple Stations Carbon Monoxide Alarms.

NFPA 72 2022 Section 17.12.4 

All carbon monoxide detectors shall be located and mounted so that accidental operation will not be caused by jarring or vibration. 

NFPA 72 2022 Section 17.12.5 

The location of carbon monoxide detectors shall be based on an evaluation of potential ambient sources and flows of carbon monoxide, moisture, temperature, dust, or fumes and of electrical or mechanical influences to minimize nuisance alarms. 

NFPA 72 Carbon Monoxide Requirements per Chapter 18

NFPA 72 2022 Section 18.4.3.1 

Where a carbon monoxide detector or alarm is required by other codes or standards or by the authority having jurisdiction and where an audible signal is required, a distinctive signal patter shall be required that is different from a fire evacuation signal.

We know this as Temporal Code 4. 

NFPA 72 2022 Section 18.4.3.2 

Where an audible signal is required, the carbon monoxide signal shall be four-pulse temporal pattern and comply with the following:

    1) Signals shall be a pattern consisting of four cycles of 100 milliseconds +/- 10 percent "on" and 100 milliseconds +/- percent "off" followed by 5 seconds +/- 10 percent "off" as demonstrated in figure 18.4.3.2

    2) After the initial 4 minutes of the carbon monoxide signal, the 5-second "off" time shall be permitted to be changed to 60 seconds +/- 10 percent.

    3) The alarm signal shall be repeated in compliance with 18.4.3.2(1) and 18.4.3.2 (2) until the alarm resets or the alarm signal is manually silenced.

NFPA 72 2022 Section 18.4.3.3

The signal shall be synchronized within a notification zone of a protected premises. 

NFPA 72 2019 Section 18.4.3.4 

The audible signal of carbon monoxide alarms and systems installed to meet the requirements of NFPA 72 chapter 29 shall NOT be required to be synchronized.

NFPA 72 2022 Section 23.8.4.9

Unless otherwise permitted by 23.8.4.9.1 signals form carbon monoxide detectors and carbon monoxide detection systems transmitted to a fire alarm system shall be indicated as a carbon monoxide alarm signal. No more general supervisory signals for carbon monoxide alarms or detection system. 

NFPA 72 2022 Section 23.8.6.1.2

Except as permitted in 23.8.61.3 occupant notification of carbon monoxide systems shall be throughout the protected premises. 

NFPA 72 2022 Section 23,8.6.1.3

Where carbon monoxide alarm signals are transmitted to a constantly attended on-site location or off-premises location in accordance with this chapter, selective public mode occupant notification zone encompassing the area where the carbon monoxide alarm signal was initiated. 

NFPA 72 2022 Section 23.8.6.3.3

The boundaries of carbon monoxide alarm notification zones shall be coincident with the area where the alarm initiation originated and other signaling zones in accordance with the building's emergency response plan. 

On another note, make sure that when you place your carbon monoxide detector outside of the sleeping area you still achieve a sound level of 75dB at the pillow with the door closed.

Read more hear about the new laws and state legislation for carbon monoxide detection in California.

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