Douglas Krantz - Technical Writer - Describing How It Works

Will Smoke in My Apartment Sound the Alarm Elsewhere?

By Douglas Krantz | Residential

Will Smoke in My Apartment Sound the Alarm Elsewhere?

Will Smoke in My Apartment Sound the Alarm Elsewhere?

Greetings Douglas,

I live in a 5 story apartment building. There is a first alert smoke detector in the celling, hard wired. There are sprinkler heads with a glass trigger in the ceiling. On the wall is a horn strobe.

There is a lot of false alarms. In my apartment, sometimes the horn strobe goes off, but never the smoke detector. Never had smoke in my place.

I noticed in the past year that the horn/strobes go off usually in 2 or maybe 3 rooms. It's possible it went in 1 room that I did not see.

Is this normal? It seems like to be safe, all the horn strobes in the building should go off if a smoke detector goes off.

If the fire code makes a difference on the rules for the fire system, I am located in San Francisco.

To me it does not make sense. I think the whole building should get the alarm if there is a fire in 1 or more rooms. If you can answer why it is like that. I would be grateful. Have a nice day.

Thank You, RO

There are two, independent, fire alarm systems in your apartment unit. Also, the sprinkler head is part of the fire suppression system (automatic fire fighting).

Fire Suppression and Fire Alarm Systems

The fire suppression system, the building sprinklers, are everywhere in the building, including the residential areas. For practical purposes, the glass trigger on each sprinkler head is a heat detector; when the air temperature is hot enough, the glass trigger breaks, the plug comes out, and that particular sprinkler head sprays water.

The fire that warmed the air below the sprinkler head gets watered and is slowed down, and sometimes, it's even stopped.

There's also a detector-switch, called a waterflow switch, that when water is being used to fight a fire, sends an alarm signal to the common area fire alarm system. When a sprinkler head sprays water in the common areas, that's a whole building alarm; when a sprinkler head sprays water in your apartment, that's a whole building alarm.

If there ever a real fire in your apartment, the fire will warm up the air above it, and break the temperature-sensitive trigger in the sprinkler head. The plug will come out of the sprinkler head, allowing water to douse the fire. Because water is flowing to douse the fire, the waterflow switch will send an alarm to the common area fire alarm system.

When the common area fire alarm system gets the alarm from the waterflow switch, the alarms will sound throughout the building. The fire department will also be dispatched.

One fire alarm system is the common area fire alarm system. It has smoke detectors in the halls, by the elevators, by the doors, and sometimes even in the basement. It also has pull stations (or MCPs - Manual Call Points) so people can sound the fire alarms. There's also an alarm input from the waterflow switch so that when any sprinkler head in the building is suppressing a fire, the alarms for the whole building sound off.

This is the system that, when activated into alarm, turns on the horns and strobes in the common areas. It also turns on the horns and (if there are any) turns on the strobes in the residential areas.

The horns and strobes connected to the common area fire alarm system don't look anything like the First Alert smoke alarm on the ceiling.

One fire alarm system is your First Alert smoke alarm on the ceiling. It is a residential, stand-alone fire alarm system. It will detect smoke, and sound the alarm, but only in your apartment. When you are cooking, and accidently burn the food, or burn-the-toast, the sounding off smoke alarm won't sound the alarm in the whole building; it will only sound the alarm in your unit.

More people die in a building fire from breathing smoke than die from flame. The purpose of the smoke alarm in the ceiling is to warn you that there's a little smoke.

The smoke alarm can tell you that there's a little smoke. However, it can't tell you how fast the smoke levels in you apartment are increasing, so if it senses even a little smoke, it sounds the alarm.

You're supposed to take action when you hear the smoke alarm. The action is to either quit burning the food, or, especially if you're asleep, get out of the apartment building while you can still breath.

If you're only burning the food, the smoke alarm shouldn't sound the common alarm so everyone else in the building has to evacuate, and it shouldn't call the fire department.

For anyone living outside your apartment, burning your food would be a false alarm.

False Alarms

The International Building Code (IBC) requires smoke alarms in residential areas, including apartments and condominiums. To prevent false alarms, they also specify that the residential smoke alarms are not to sound the fire alarms in the entire building, just in the individual apartment or condo.

Three Systems

  1. There's the smoke alarm in your apartment, warning you to get out while you can still breathe

  2. There's the building-wide common-area fire alarm system, warning you to get out right away

  3. There's the sprinkler system, suppressing fires and sending alarms to the common fire alarm system

Douglas Krantz
Life Safety
This website uses cookies. See Privacy for details.
Fire Alarm Q&A Articles

No Charge - Unsubscribe Anytime

Make It Work Series of Books by Douglas Krantz
Free - Click and Download
Make It Work Series of Books by Douglas Krantz
Make It Work Series of Books by Douglas Krantz