This article is from an archived issue and may contain out-of-date information. Please refer to the main Codes & Standards page for more current articles. Duct DetectorsThe Smoke Detectors Everyone Loves To Hate February 2011 © 2003 - 2016. All Rights Reserved.Electrical Contractor: 3 Bethesda Metro Center, Suite 1100, Bethesda, MD. What you will learn from Duct Detectors Smoke Detection - NFPA 90A Code Requirements article:Preface for the NFPA 90A requirements for duct detectors in air conditioning and heating equipment.The question: Where do you install duct detectors in duct work?detailed answer to satisfy requirementsexclusions and exceptions to the requirementreferences for further information about HVAC equipment and fire safetyFinally, additional related information about fire and smoke dampers regarding HVACDuct Detectors Smoke Detection - NFPA 90A Code RequirementsThis article references the current NFPA 90A “Standard for the Installation of Air-Conditioning and Ventilating Systems” and provides basic instruction on the installation of smoke detectors inside the duct work.

NFPA 90A is specific to Air Conditioning and Heating Systems installation. The purpose of the NFPA 90A is to prevent the spread of smoke and fire through duct work and ventilation systems for air conditioning and heating systems with high capacities. Modern Curtains And ValancesAlways ensure you check the latest codes for current information. Hot Tub Speaker KitAdditionally, some municipalities have more stringent codes in place. American Standard Toilets Consumer ReviewsTherefore, it is wise to check local code requirements in addition to current national codes. Get your copy here: NFPA 90a: Standard for the Installation of Air-Conditioning and Ventilating SystemsDuct Detectors Smoke Detection - NFPA 90A Code RequirementsQuestion: Where to place smoke detectors in the duct work on commercial projects to comply with code?

In this case the NFPA 90A requirements for HVAC systems and duct work. The NFPA 90A is specific in defining the position of the duct smoke detectors in the duct work. The code details why smoke detectors are required along with the intentions of installing duct smoke detectors inside the duct work to comply with code requirements. The question is: Where do you install these devices in the duct work? Duct Detectors Smoke Detection - NFPA 90A Code Requirements - The Basic Rundown for Field Installations2000 CFM’sIn multi-story buildings at each story with a common shared return and having a capacity greater than 15,000 CFM’s. The smoke detection device should be installed before the connection to the common return and before any connection to any recirculation or fresh air inlet in the return air systems. The code includes plenums where the plenum is used for a common return.Duct Smoke Detection - NFPA 90A Code Requirements – There are exceptions to the two basic requirements:Return air smoke detectors are not required when there is protection of the space served by a system of area smoke detectors.2015 International Mechanical Code

Additional references to smoke detector safety in air conditioning and heating systems installation can be found using the following resources:The Joint Commission/NFPA Life Safety Book for Health Care OrganizationsU.L. Standard 269A, Standard for Smoke Detectors for Duct ApplicationsDuct Detectors Smoke Detection - NFPA 90A Code RequirementsIn addition to the installation requirements for smoke dampers and fire dampers the code requirement for any safety devices in duct work ventilation systems is necessary for basic life and safety. Engineering drawings typically have the location of installation to comply with code requirements. Engineering drawings do not always represent these details. Following up with a Request for Information can hold the job up sometimes.Additionally a good technician will educate themselves on the proper installation of any essential component. And especially for the installation of air conditioning and heating equipment and components required by code.

Always read the manufacturers instructions, guidelines, and recommendations when installing and testing smoke detectors in duct work. Special requirements for installation and successful operation makes it necessary for a trouble free installation. Remember, others will be testing installation including the code inspector, fire inspectors  and commissioning people.Duct Detectors Smoke Detection - NFPA 90A Code Requirements ConclusionFurthermore, intentions for using duct smoke detectors should not be a substitute for area smoke detectors. Nor should it serve as an early warning detection system. Therefore, they should complement the buildings fire detection system and not serve as the primary fire detection system. Additionally, always follow the code requirements for each project. If you do not understand the code or the requirements ask the engineer or other qualified person on the project.For more on smoke detectors click here.Duct Detectors Smoke Detection - NFPA 90A Code Requirements

A fire starts in your building – an alarm sounds, fire doors activate, and occupants rush outside to safety. But what about your HVAC system? "In an emergency, air duct systems can transfer smoke, toxic gases, and flame from one area to another, posing a serious hazard to life safety and property," explains Jim Kapparos, national sales manager for System Sensor, a manufacturer of fire alarm systems. Take the infamous 1980 MGM Grand fire. While the fire was contained to the lower levels of the casino, most of the 85 deaths occurred on the upper floors from smoke inhalation and carbon monoxide poisoning. Faulty dampers accelerated the spread of dangerous fumes to stairwells and emergency passageways. According to the official investigation report by NFPA, "the distribution of smoke throughout the high-rise tower through the heating, ventilation, and air equipment" was a major factor contributing to the death toll. To safeguard your ductwork from becoming a pathway for fire, make sure your facility is protected by duct smoke detectors.

How Do They Work? Duct detectors sample currents in the air handling equipment to determine if smoke or fumes are present. If smoke is detected, the device will close dampers, stop fans and blowers, and trigger an audible and visible signal at the fire control panel, Kapparos explains. These actions provide early detection, allow facility personnel to investigate the cause, and can protect the air conditioning system itself from fire and smoke damage. Typically found in large commercial and industrial facilities, duct smoke detectors are a code-mandated device where required by NFPA 72 (90A), NFPA 101, and the International Mechanical Code (IMC), says Kapparos. Stipulations can also be found in the International Building Code, International Fire Code, and the Life Safety Code 101, adds Bernie Arends, who served as an origin and cause fire investigator for over 30 years and works as a sales associate for Inspection Reports Online. While local code adoption varies, duct smoke detectors are most common for facilities with 5-ton or more cooling units.

"Duct smoke detectors are needed on HVAC units over 2000 cfm on the return side, and on units over 15,000 cfm on the supply and return sides," says Arends. Some can also be interconnected to other duct detectors. If one senses smoke, the rest will switch their relays, with the triggered detector reporting to the fire alarm panel so the source can be pinpointed. Like any other fire safety components, duct detectors need routine upkeep and testing to remain effective. Dust, dirt, and other foreign matter can accumulate inside a detector and change its sensitivity, which may cause unwanted alarms or reduce the level of protection, Kapparos says. "The installing contractors must provide the owner with cut sheets for these critical life safety devices," notes Arends. "Preventive maintenance and servicing information is specific to each manufacturer and should be strictly adhered to." At minimum, Kapparos suggests these regular measures: Visually inspect detectors every six months to confirm that they are in a normal operating state.

Test annually by causing units to initiate an alarm at their installed location, ensuring they produce the intended response. Check within one year after installation and every alternate year thereafter to assure devices are within their listed and marked sensitivity range. Test or inspect annually to ensure detectors sample the air stream. Because the units are often hard to reach, remote test/reset switches that are easy to see and access should be installed within close proximity of the unit, says Ahrends. Most sensors use LEDs to indicate if the device is operating outside its preset sensitivity range. To check the detectors, differential pressure testing can be used, though some jurisdictions require smoke bombs. If you find that a sensor requires cleaning, use a vacuum cleaner, compressed air, or dry nitrogen to remove dust and debris, recommends Kapparos. Big Benefits, Little Costs Duct smoke detectors are modestly priced, ranging from $125 to several hundred dollars, estimates Arends.