--- title: What are the Different Types of Fire Alarm Initiating Devices? description: Fire alarm systems are a complex network of many different interconnected components that all play a unique role in fire protection. image: https://blog.koorsen.com/hubfs/ASA%20chamber%20Detector%20600x400.jpg --- [![Koorsen Fire & Security](https://blog.koorsen.com/hs-fs/hubfs/KoorsenFireSecurity_April2017/Images/koorsen-logo.png?width=209&height=50&name=koorsen-logo.png "Koorsen Fire & Security")](https://www.koorsen.com/) [CONTACT US](https://www.koorsen.com/contact-us/) [BILL PAY](https://www.koorsen.com/koorsen-payments/) [1.866.311.7753](tel:8663117753) - [About Us](https://www.koorsen.com/about-us/) - [History](https://www.koorsen.com/about-us/history/) - [Case Studies](https://blog.koorsen.com/case-studies) - [Koorsen Companies](https://www.koorsen.com/about-us/companies/) - [Koorsen Training Center](https://www.koorsen.com/about-us/training-center/) - [Kasey Program](https://www.koorsen.com/about-us/kasey-program/) - [Pay Bill](https://www.koorsen.com/koorsen-payments/) - [Products + Services](https://www.koorsen.com/products-services/) - [Fire Protection](https://www.koorsen.com/products-services/fire-protection/) - [Security](https://www.koorsen.com/products-services/security/) - [Communications](https://www.koorsen.com/products-services/communications/) - [Mobile Equipment Solutions](https://www.koorsen.com/products-services/mobile-equipment-solutions/) - [Additional Products + Services](https://www.koorsen.com/products-services/#additional) - [Industries](https://www.koorsen.com/industries/) - [Healthcare](https://www.koorsen.com/industries/healthcare/) - [Industrial](https://www.koorsen.com/industries/industrial/) - [Education](https://www.koorsen.com/industries/education/) - [Restaurants](https://www.koorsen.com/industries/restaurants/) - [Property Management](https://www.koorsen.com/industries/property-management/) - [Hospitality](https://www.koorsen.com/industries/hospitality/) - [Retail](https://www.koorsen.com/industries/retail/) - [Construction](https://www.koorsen.com/industries/construction/) - [Locations](https://www.koorsen.com/locations/) - [News](https://blog.koorsen.com) - [Koorsen Blog](https://blog.koorsen.com) - [Koorsen In The News](https://www.koorsen.com/in-the-news/) - [Kasey the Dog Blog](https://blog.koorsen.com/kaseys-adventures) - [Careers](https://www.koorsen.com/about-us/careers/) # What are the Different Types of Fire Alarm Initiating Devices? Posted August 07, 2020 by [Koorsen Fire & Security](https://blog.koorsen.com/author/koorsen-fire-security) ![ASA chamber Detector 600x400](https://blog.koorsen.com/hs-fs/hubfs/ASA%20chamber%20Detector%20600x400.jpg?width=600&name=ASA%20chamber%20Detector%20600x400.jpg) Fire alarm systems – they protect most businesses, [schools](https://www.koorsen.com/industries/education/), hospitals, hotels, and multi-family dwellings from the tragedy of a fire. While it is easy to take them for granted and thus oversimplify them, [fire alarm systems](https://www.koorsen.com/products-services/fire-protection/fire-alarm-systems/) are a complex network of many different interconnected components that all play a unique role in fire protection. The most visible component of these systems, and likely the one you are most familiar with, is the fire alarm initiating device. [![Fire Alarm System Questions? Click to Contact Us Now!](https://no-cache.hubspot.com/cta/default/1973249/b3a8ea3b-70d2-46e9-be6d-f07129820e82.png)](https://cta-redirect.hubspot.com/cta/redirect/1973249/b3a8ea3b-70d2-46e9-be6d-f07129820e82) ## What are Fire Alarm Initiating Devices? The initiating devices in a fire alarm system are those that detect signs of a possible fire and activate an alarm. They are the system’s triggers and the most visible aspect of the fire alarm system. Initiating devices are connected to the alarm system’s control panel via 2- or 4-way circuits and are under the control panel’s constant surveillance. When an initiating device is activated, the panel identifies the activation and goes into an alarm state, sounding the alarm in the building and sending a call out for an emergency response. Fire alarm initiating devices include [smoke detectors](https://blog.koorsen.com/how-to-fix-beeping-smoke-detectors), sprinkler water flow switches, manual [fire alarm pull stations](https://blog.koorsen.com/what-are-the-requirements-for-a-fire-alarm-pull-station), and more. ## Types of Fire Alarm Initiating Devices All initiating devices can be categorized into one of two types: **automatic initiating devices** and **manual initiating devices**: - **Automatic initiating devices:** automatic devices are those that are triggered automatically by the right conditions. These include: - smoke detectors - fire sprinkler water flow switches - heat detectors Among automatic initiating devices, there are spot type devices and linear type devices. Spot type devices are detectors that focus solely on their area where they have been installed, while linear types have a method of detection that covers a wide area of space but communicates to a single control unit. A standard [ionization smoke alarm](https://blog.koorsen.com/what-is-the-difference-between-ionization-and-photoelectric-smoke-alarms) is an example of a spot type, while a light-obscuration photoelectric smoke detector is an example of a linear type (more on both of these below). While spot types are cheaper, each device must be hooked up to the [fire alarm system](https://www.koorsen.com/products-services/fire-protection/fire-alarm-systems/) separately, and more must be installed to cover the space adequately. In contrast, linear types, while more expensive, only require one hook up to the fire alarm system, and one unit covers a greater area. - **Manual initiating devices:** manual devices are ones that must be / can be activated manually by a person when they witness a fire emergency. This, of course, refers to a manual pull station. When one of these devices is activated by their respective conditions (smoke, heat, water flow, or manual adjustment), the change is detected by the control panel and initiates the alarm state, at which point the fire alarm system sets off audible and visual alarms to notify building occupants of the hazard. ## How do Initiating Devices Work? Most fire alarm systems will have multiple types of initiating devices, and each fire alarm initiating device has its unique role and triggering requirements. Each initiating device must be individually installed and connected to the fire alarm system’s circuitry. Once installed and connected, these devices just have to operate as they normally do to detect a fire and activate to alert the system. Following are brief explanations of how each of the main types of initiating devices work: - **Smoke Detectors**: smoke detectors are excellent, rapidly responding initiating devices that help fire alarm systems respond before a fire has a chance to develop fully. This is because fires cause smoke early in their development, long before the heat of a fire sets off water sprinklers or heat detectors. There are two main types of smoke detectors: ionization and photoelectric. Ionization smoke detectors use ionized air held within a sensing chamber to measure the airflow current. When smoke infiltrates the chamber, it reduces the current. When the current drops enough, the detector is activated. Photoelectric smoke detectors use one of two methods to use light to detect smoke. One method is called light-scattering, where a light source and a sensor are arranged (both within the detector) in such a way that the sensor does not detect the light under normal conditions. When smoke enters into the detector, it causes the light to scatter or reflect into the sensor. When enough light hits the sensor, it is activated. The other photoelectric method is light obscuration, where the light source and detecting sensor are usually two separate components. A light beam is projected into the sensor, and as long as the sensor receives the light, it remains inactive. But if smoke from a fire fills the air and obscures the light beam from the sensor, the detector is activated. - **Sprinkler Water Flow Switches**: a sprinkler water flow switch is a device inside of a [fire sprinkler system](https://www.koorsen.com/products-services/fire-protection/fire-sprinkler-systems/) that detects the flow of water through the pipes of the system. Typically, when a sprinkler system has not been activated, stagnant water sits in the pipes. But, when a fire sprinkler is activated by fire-induced temperatures, water begins to flow through the system and out of the open fire sprinkler. The sprinkler water flow switch senses this change in the water activity and signals the fire alarm control panel that the sprinkler system has been activated. - **Heat Detectors**: heat detectors are the oldest form of automatic initiating devices and are still the most reliable, though often slowest to react to a fire. There are a few types, most commonly the fixed temperature detectors and the rate-of-rise detectors. Fixed-rate heat detectors are preset to activate when the temperature within the room reaches a specific, predetermined temperature. Unfortunately, a fire can have a long time to grow before the temperature reaches this predetermined level, so there is a lag between the fire starting and the initiating device activating. A rate-of-rise heat detector, on the other hand, is activated when the temperature around the detector rises 15 degrees or more in a minute. The air within the detector’s chamber expands in response to this rapid increase in temperature and presses a flexible metal diaphragm against contacts in the chamber that triggers activation. While rate-of-rise heat detectors are typically faster to detect fires, they still require a fire to get started and grow before they activate, which is why they should be used in combination with other initiating devices and not solely relied upon. - **Manual Pull Stations**: famously portrayed in many films as an easy means of escaping awkward situations, manual pull stations allow individuals to initiate the fire alarm in case of an emergency. Pull stations may either be single- or dual-action. In single-action stations, only the single physical act of pulling a lever is required to activate the alarm. In contrast, in dual-action stations, two acts are required, such as first breaking a glass cabinet containing the lever, or lifting a covering to access the lever. In most systems, once the lever is pulled, a signal is sent to the control panel, and a general alarm is sounded throughout the entire building alerting everyone to evacuate the building. Though each of these [fire alarm initiating devices](https://www.koorsen.com/products-services/fire-protection/fire-alarm-systems/) is activated in response to unique conditions, their overall role within a fire alarm system is the same – to activate in response to a fire, thus signaling the fire alarm control panel to go into alarm mode. They **initiate** the alarm. ## Choosing the Right Fire Alarm Initiating Devices for Your System As should now be evident, there are many types of initiating devices, and the ones listed above only represent the main ones. There are plenty of other types, as well as possible customizations to each. As each device is initiated by a different set of conditions, it is vital to understand that no alarm system should only rely on just one type. While sprinkler water flow switches and heat detectors do an excellent job protecting a building by notifying the system of a fire, they do not activate early enough to protect the life within that building. That’s why smoke detectors and other devices are also necessary to create a truly life-saving fire alarm system. However, your facility’s unique conditions, materials, layout, and staffing or residents all impact which type of fire alarm initiating devices would work best and where they ought to be placed. To effectively protect your property and the lives who live or work there, you need the help of experts like [Koorsen Fire & Security](https://www.koorsen.com/) who have made it their business to know the ins and outs of these systems and devices for the last 70 plus years. Don’t leave the protection of life and property to chance – give the experts at Koorsen a call today. They can help you care for your current system or help you choose and design a system that will best protect your people and property. [![Fire Alarm System Questions? Click to Contact Us Now!](https://no-cache.hubspot.com/cta/default/1973249/b3a8ea3b-70d2-46e9-be6d-f07129820e82.png)](https://cta-redirect.hubspot.com/cta/redirect/1973249/b3a8ea3b-70d2-46e9-be6d-f07129820e82)   - [Tweet](https://twitter.com/share) Topics: [Fire Protection](https://blog.koorsen.com/topic/fire-protection), [Fire Alarm Systems](https://blog.koorsen.com/topic/fire-alarm-systems) ## Contact Us Now! *Disclaimer: The information in this article is for informational purposes only. It is believed to be reliable, but Koorsen Fire & Security assumes no responsibility or liability for any errors or omissions in the content of this article. It does not constitute professional advice. The user of this article or the product(s) is responsible for verifying the information's accuracy from all available sources, including the product manufacturer. The authority having jurisdiction should be contacted for code interpretations.*  ### Related posts [Overview and FAQs of NFPA 101](https://blog.koorsen.com/overview-and-faqs-of-nfpa-101) [Overview of NFPA 99, Health Care Facilities Code](https://blog.koorsen.com/overview-of-nfpa-99-health-care-facilities-code) [Code Requirements for Commercial Fire Protection](https://blog.koorsen.com/code-requirements-for-commercial-fire-protection) [Design Considerations for Commercial Fire Protection](https://blog.koorsen.com/design-considerations-for-commercial-fire-protection) [Advances In Commercial Fire Protection Technology](https://blog.koorsen.com/advances-in-commercial-fire-protection-technology) [![Questions! Contact Us Now!](https://no-cache.hubspot.com/cta/default/1973249/27550866-4d2c-46fb-8ec4-ef118de52673.png)](https://cta-redirect.hubspot.com/cta/redirect/1973249/27550866-4d2c-46fb-8ec4-ef118de52673) ### SEARCH OUR BLOG This is a search field with an auto-suggest feature attached. - There are no suggestions because the search field is empty. ### Subscribe to Our Blog ### Recent Posts ### CATEGORIES - [Commercial Security (111)](https://blog.koorsen.com/topic/commercial-security) - [Fire Protection (109)](https://blog.koorsen.com/topic/fire-protection) - [Fire Extinguisher (77)](https://blog.koorsen.com/topic/fire-extinguisher) - [Fire Alarm Systems (75)](https://blog.koorsen.com/topic/fire-alarm-systems) - [Fire Safety & Security (73)](https://blog.koorsen.com/topic/fire-safety-security) - [Koorsen News (73)](https://blog.koorsen.com/topic/koorsen-news) - [Fire Sprinkler Systems (67)](https://blog.koorsen.com/topic/fire-sprinkler-systems) - [Fire Safety (61)](https://blog.koorsen.com/topic/fire-safety) - [Access Control Systems (45)](https://blog.koorsen.com/topic/access-control-systems) - [Fire Suppression (43)](https://blog.koorsen.com/topic/fire-suppression) - [Inspection/Testing (43)](https://blog.koorsen.com/topic/inspectiontesting) - [Small Business Security (39)](https://blog.koorsen.com/topic/small-business-security) - [Kitchen Fire Suppression (37)](https://blog.koorsen.com/topic/kitchen-fire-suppression) - [Video Surveillance (30)](https://blog.koorsen.com/topic/video-surveillance) - [Fire Training (24)](https://blog.koorsen.com/topic/fire-training) - [Restaurant Industry (24)](https://blog.koorsen.com/topic/restaurant-industry) - [Emergency/Exit Lighting (22)](https://blog.koorsen.com/topic/emergency-exit-lighting) - [Monitoring (20)](https://blog.koorsen.com/topic/monitoring) - [NFPA (19)](https://blog.koorsen.com/topic/nfpa) - [Education Industry (18)](https://blog.koorsen.com/topic/education-industry) - [Commercial Kitchen (17)](https://blog.koorsen.com/topic/commercial-kitchen) - [Training & Education (15)](https://blog.koorsen.com/topic/training-education) - [Fire Pumps (12)](https://blog.koorsen.com/topic/fire-pumps) - [Healthcare Industry (12)](https://blog.koorsen.com/topic/healthcare-industry) - [Property Management Industry (10)](https://blog.koorsen.com/topic/property-management-industry) - [Bi-Directional Amplifier (9)](https://blog.koorsen.com/topic/bi-directional-amplifier) - [Emergency Notification (9)](https://blog.koorsen.com/topic/emergency-notification) - [General (9)](https://blog.koorsen.com/topic/general) - [Nurse Call System (9)](https://blog.koorsen.com/topic/nurse-call-system) - [Kasey Program (8)](https://blog.koorsen.com/topic/kasey-program) - [Restaurant (8)](https://blog.koorsen.com/topic/restaurant) - [Education (7)](https://blog.koorsen.com/topic/education) - [Property Management (7)](https://blog.koorsen.com/topic/property-management) - [Construction Industry (6)](https://blog.koorsen.com/topic/construction-industry) - [Koorsen Family Foundation (6)](https://blog.koorsen.com/topic/koorsen-family-foundation) - [Press (6)](https://blog.koorsen.com/topic/press) - [Retail Industry (6)](https://blog.koorsen.com/topic/retail-industry) - [Mobile Equipment (4)](https://blog.koorsen.com/topic/mobile-equipment) - [Vehicle Fire Suppression (4)](https://blog.koorsen.com/topic/vehicle-fire-suppression) - [Awards (3)](https://blog.koorsen.com/topic/awards) - [Dry Chem Suppression (3)](https://blog.koorsen.com/topic/dry-chem-suppression) - [Engineering (3)](https://blog.koorsen.com/topic/engineering) - [Hospitality Industry (3)](https://blog.koorsen.com/topic/hospitality-industry) - [Long Term Care (3)](https://blog.koorsen.com/topic/long-term-care) - [Podcast (3)](https://blog.koorsen.com/topic/podcast) - [Industrial (2)](https://blog.koorsen.com/topic/industrial) - [Infographics (2)](https://blog.koorsen.com/topic/infographics) - [KnoxBox (2)](https://blog.koorsen.com/topic/knoxbox) - [Backflow Preventer (1)](https://blog.koorsen.com/topic/backflow-preventer) - [Construction (1)](https://blog.koorsen.com/topic/construction) - [Distributed Antenna Systems (1)](https://blog.koorsen.com/topic/distributed-antenna-systems) - [Flame Detection (1)](https://blog.koorsen.com/topic/flame-detection) - [Government (1)](https://blog.koorsen.com/topic/government) - [Home Security (1)](https://blog.koorsen.com/topic/home-security) - [The Joint Commission (1)](https://blog.koorsen.com/topic/the-joint-commission) - [Underground Services (1)](https://blog.koorsen.com/topic/underground-services) see all ### ALL PRODUCTS AND SERVICES - [Fire Extinguishers](https://www.koorsen.com/products-services/fire-protection/fire-extinguishers/) - [General Fire Products](https://www.koorsen.com/products-services/fire-protection/general-fire-products/) - [Emergency/Exit Lighting](https://www.koorsen.com/products-services/fire-protection/emergency-exit-lighting/) - [Fire Alarm Systems](https://www.koorsen.com/products-services/fire-protection/fire-alarm-systems/) - [Fire Sprinkler Systems](https://www.koorsen.com/products-services/fire-protection/fire-sprinkler-systems/) - [Kitchen Fire Suppression](https://www.koorsen.com/products-services/fire-protection/kitchen-hood-fire-suppression/) - [Fire Suppression Systems](https://www.koorsen.com/products-services/fire-protection/fire-suppression-systems/) - [Commercial Security](https://www.koorsen.com/products-services/security/commercial-security/) - [Emergency Notification](https://www.koorsen.com/products-services/communications/emergency-notification/) - [Communications](https://www.koorsen.com/products-services/communications/) - [Home Security](https://www.koorsen.com/products-services/security/home-security/) - [Nurse Call Systems](https://www.koorsen.com/products-services/communications/nurse-call-systems/) ### OTHER COMPANIES - [KOORSEN ENVIRONMENTAL](https://koorsenes.com/) - [KOORSEN FACILITIES MANAGEMENT](https://www.koorsenfm.com/) ### CONTACT KOORSEN [866-311-7753](tel:8663117753) [info@koorsen.com](mailto:info@koorsen.com) - [FAQS](https://www.koorsen.com/faq/) - [KOORSEN CAREERS](https://www.koorsen.com/about-us/careers/) - [MEDIA RELATIONS](https://www.koorsen.com/media-relations/) - [TRANSPARENCY IN COVERAGE](https://www.koorsen.com/transparency-in-coverage/) © 2026 Koorsen Fire & Security | [PRIVACY POLICY](https://www.koorsen.com/privacy-policy/) ```json { "@context" : "https://schema.org", "@type" : "BlogPosting", "author" : { "@type" : "Person", "name" : "Koorsen Fire & Security", "url" : "https://blog.koorsen.com/author/koorsen-fire-security" }, "dateModified" : "2025-06-16T19:10:12.133Z", "datePublished" : "2020-08-07T13:28:45.000Z", "headline" : "What are the Different Types of Fire Alarm Initiating Devices?", "image" : [ "https://blog.koorsen.com/hubfs/ASA%20chamber%20Detector%20600x400.jpg" ], "mainEntityOfPage" : { "@id" : "https://blog.koorsen.com/what-are-the-different-types-of-fire-alarm-initiating-devices", "@type" : "WebPage" }, "publisher" : { "@type" : "Organization", "logo" : { "@type" : "ImageObject", "url" : "https://blog.koorsen.com/hubfs/KoorsenFireSecurity_April2017/Images/koorsen-logo.png" }, "name" : "Koorsen Fire & Security - - -" } } ``` ```json { "@context" : "http://schema.org", "@type" : "Organization", "address" : { "@type" : "PostalAddress", "addressCountry" : "", "addressLocality" : "Indianapolis", "addressRegion" : "IN", "postalCode" : "46218", "streetAddress" : "2719 N Arlington Ave " }, "alternateName" : "Koorsen", "description" : "Since 1946, people have trusted Koorsen to protect and secure their businesses and homes.", "email" : "https://www.koorsen.com/", "image" : "https://blog.koorsen.com/hs-fs/hubfs/KoorsenFireSecurity_April2017/Images/koorsen-logo.png?width=209&name=koorsen-logo.png", "logo" : "https://cdn2.hubspot.net/hubfs/1973249/KoorsenFireSecurity_April2017/Images/koorsen-logo.png", "mainEntityOfPage" : { "@id" : "https://blog.koorsen.com/what-are-the-different-types-of-fire-alarm-initiating-devices", "@type" : "WebPage", "description" : "Fire alarm systems are a complex network of many different interconnected components that all play a unique role in fire protection." }, "naics" : "238220", "name" : "Koorsen Fire & Security Headquarters", "sameAs" : [ "https://www.facebook.com/pages/Koorsen-Fire-Security/173081436052031", "https://twitter.com/koorsenfire", "http://www.linkedin.com/company/koorsen-fire-and-security", "https://www.youtube.com/channel/UCU0ncdcrEYAjDHIcGGgJ3KQ", "https://www.instagram.com/koorsenfire/?hl=en" ], "telephone" : "", "url" : "https://www.koorsen.com/" } ``` ```json { "@context" : "http://schema.org", "@type" : "BlogPosting", "author" : { "@type" : "Person", "name" : "Koorsen Fire & Security" }, "dateModified" : "June 16, 2025, 7:10:12 PM", "datePublished" : "2020-08-07 13:28:45", "description" : "Fire alarm systems are a complex network of many different interconnected components that all play a unique role in fire protection.", "headline" : "What are the Different Types of Fire Alarm Initiating Devices?", "image" : { "@type" : "ImageObject", "url" : "https://f.hubspotusercontent40.net/hubfs/1973249/ASA%20chamber%20Detector%20600x400.jpg" }, "mainEntityOfPage" : { "@id" : "https://blog.koorsen.com/what-are-the-different-types-of-fire-alarm-initiating-devices", "@type" : "WebPage" }, "publisher" : { "@type" : "Organization", "logo" : { "@type" : "ImageObject", "url" : "https://cdn2.hubspot.net/hubfs/1973249/KoorsenFireSecurity_April2017/Images/koorsen-logo.png" }, "name" : "Koorsen Fire & Security Headquarters" } } ```