Technology: Smoke Alarms vs Smoke Detectors

John Larkin, ESC Senior Partner (image)Technology: Smoke Alarms vs Smoke Detectors | #ESC_LCC #SmokeAlarm #FireCode #Technology | There’s a difference between Smoke Alarms and Smoke Detectors. Do they have an expected end of life? Perhaps it’s time you find out what you have and what you’re supposed to do with it.

“Smoke Alarms Are Self-Contained smoke detection devices that contain their own source of operating power. They are, in fact, capable of operating in standalone using their own self-contained power source and a means of notification,” says John Larkin, Senior Partner with ESC of Greater Ohio. “Smoke detectors, on the other hand, detect smoke as well–but they work in tandem with a centralized alarm control panel that provides power as well as a means of building/house-wide notification.”

Where smoke alarms usually are installed by homeowners, smoke detectors must be installed by professional fire alarm technicians–in many cases individuals licensed by the state where the work is performed.

In this ESC blog article we’ll take a look at both types of fire detection with an eye toward commercial.

What Fire Code Says

Smoke Detector (image)
An ESC technician installs a smoke detector.
When we examine Section 3.3.265, 2016 edition, NFPA 72, National Fire Code, it’s obvious there are two types of smoke alarms we must consider (their official names): 1) single station, and 2) multiple station.

Section 3.3.260, defines a single-station smoke alarm as, “An assembly that incorporates the detector, the control equipment, and the alarm sounding device in one unit operated from a power supply either in the unit or obtained at the point of installation.”

In other words, a smoke alarm is a self-contained unit that detects and notifies within a single unit. They can be powered by 120VAC or by a 9V battery, and in some cases both. In this case the 9V battery serves as a backup power sourced when house power fails.

Multiple-station alarm devices share the same characteristics as a single-station alarm with the exception that instead of operating solo, these devices can be interconnected so when one unit goes off, all units go off.
In our next posting, we’ll talk about smoke detectors and how they work. If you have any questions, please feel free to call us at 614-754-1393, email or on the web

Detecting the Difference Between Smoke Alarms and Detectors

Alarm control panel (image)
An alarm control panel operated by an ESC technician during a routine fire inspection.
While looking for notable news for our Social Media channels, I often find that newspapers and magazines use the terms “smoke alarm” and “smoke detector” interchangeably when there’s a significant difference between the two.

As previously mentioned, the technical side of the fire alarm business often turns on interchangeable terms, such as fire sensors, fire alarms and fire detectors. There are times, however, when these fire terms cannot be interchanged without altering the technological issues or specific code considerations. A good example of this is automatic smoke alarms vs. smoke detectors. In Section 3.3.265, 2016 Edition, it says a smoke alarm is “A single or multiple-station alarm responsive to smoke.”

In Section 3.3.66, 2016, it says a detector is “A device suitable for connection to a circuit that has a sensor that responds to a physical stimulus such as heat or smoke.” This month, we will explore some of the more notable details concerning both methods of fire protection and how they differ in the real world.

Fire alarm control keypad with a manual fire  pull (image)Smoke Detectors Use a Supervised Circuit

When we examine the definition of a smoke detector, as contained in Section 3.3.267, 2002 Edition, we find another code reference: Section 3.3.66, Detector. Here it says, “A device suitable for connection to a circuit that has a sensor that responds to a physical stimulus such as heat or smoke.”

The key to defining the difference between the two types of smoke detection units is actually contained in Section 8-1.4.4 of NFPA 72, 2007 Edition. Here it says, “Smoke detectors shall be connected to central controls for power, signal processing, and activation of notification appliances.”

Within the same section it specifies the number of smoke detectors that can be placed on a single initiating circuit. It also defines the number of multiple -station smoke alarms that can be placed on a single circuit, or tandem line, as it’s often called. “Smoke alarms shall not be interconnected in numbers that exceed the manufacturer ’s recommendations, but in no case shall more than 18 initiating devices be interconnected (of which 12 can be smoke alarms) where the interconnecting means is not supervised, or more than 64 initiating devices be interconnected (of which 42 can be smoke alarms) where the interconnecting means is supervised.”

The last portion of the above code refers to smoke detectors that utilize supervision to maintain the integrity of the initiating circuit. Here, up to 42 smoke detector units can be installed on a supervised initiating circuit that allows for up to 64 devices. In a smoke alarm circuit, however, only 12 smoke alarms can be used in a non-supervised initiating circuit that allows for up to 18 devices. In this case, the initiating circuit interconnects each single station unit so that when one goes off they all go off.

John Larkin on the job (image)
John Larkin, Senior Partner with ESC, on the job.
Smoke detectors derive their operating power from a centralized source, usually a fire alarm control panel. Although these devices usually possess a means of signal processing, it is the fire alarm control panel that provides notification appliances with the signal they require to sound off. In most cases, this notification appliance is separate from the smoke detector, but not always. In the case of smoke alarms, a notification appliance must be provided

internal to each smoke alarm device. However, in the former, the means of notification appliance activation is usually external to the smoke detectors.

If you have questions about smoke alarms versus detectors, feel free to reply to this post, or send me an email at Thanks!

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Analog camera with LED illumination (image)Did you know that you might be able to use your video surveillance system to detect a fire? | #ESC_LLC #VideoSurveillance #Video #Fire #FireAlarm | According to Section A. of NFPA 72, 2013 Edition, “Video Image Smoke Detection (VISD). Video image smoke detection (VISD) is a software-based method of smoke detection that has become practical with the advent of digital video systems. Listing agencies have begun testing VISD components for several manufacturers. VISD systems can analyze images for changes in features such as brightness, contrast, edge content, loss of detail, and motion. The detection equipment can consist of cameras producing digital or analog (converted to digital) video signals and processing unit(s) that maintain the software and interfaces to the fire alarm control unit. For more info:

Allan Colombo, ESC Media Director
Allan Colombo, ESC Media Director
Email: ESC@Tpromo.Com
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Human Investigation Management – ISIO (logo, image)
Human Investigation Management – ISIO