Smoke Detector Details and Placement

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Old 08-25-08, 05:23 PM
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Smoke Detector Details and Placement

Just double checking NEC code specs for what's required in smoke alarms. I know they are required in BR's. Is the hall outside BR's required or just a good idea? I was planning on putting one in the hall, too, but then reading the smoke alarm's own instructions it says not to put within 3' of a bathroom door if it has a tub/shower, nor within 3' of any high air volume device such as a whole house fan.

As luck would have it, my tiny hallway between the two BR's has BOTH a door to the only bath and a whole house fan. There's no place in the hall that is more than 3' away from either. So I'm wondering if a detector is required there. I certainly don't want it going off every time someone takes a shower or the whole house fan is in use.

Also - is the battery backup a requirement by NEC code? Or is that requirement more a municipal thing that varies from place to place?
 
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Old 08-25-08, 05:37 PM
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Is that a second floor hallway? If it is, I would place it at the bottom of the stairs.
 
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Old 08-25-08, 06:16 PM
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This is just a small, one story house. 2 BR, 1 BA, less than 1200 sq. ft total. The bedroom doors are probably 10' away from each other max. That's about the length of the hall.
 
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Old 08-25-08, 07:00 PM
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The requirements for smoke detectors is not in the NEC. This is covered by the building code.

Off the top of my head it is 1/ bedroom, 1 outside sleeping areas, and 1 on all the other levels.

Perhaps you could mount the hallway one on the wall?
 
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Old 08-26-08, 07:32 AM
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Ionization alarms are more prone to false alarms from steam/cooking than Photoel

Hello,


Ionization alarms are more prone to false alarms from steam/cooking than Photoelectric alarms. Additionally, ionization smoke alarms tend to respond poorly to particulate from smoldering fires.

Check out the Barre City Vermont Fire Department for additional information: http://www.smokealarminfo.com/

You can also google: photoelectric ionization and you will obtain much more information.

Tim McGreal
Professional Fire Protection Engineer
 
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Old 08-26-08, 08:48 AM
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Originally Posted by cakins View Post
Just double checking NEC code specs for what's required in smoke alarms.
The only NEC requirement for smoke alarms is that they must be protected with an AFCI breaker. Placement of detectors is covered by your jurisdiction's building code.

I know they are required in BR's...
I go with one per bedroom plus one per floor. Also if there are gas-burning appliances or any fireplaces, I make at least one per floor a combo smoke / carbon monoxide detector. Some people choose to also include a heat detector in the attached garage.

I certainly don't want it going off every time someone takes a shower or the whole house fan is in use.
Modern detectors are pretty good at preventing false trips caused by the shower. Furthermore, if you have an adequate vent fan in the bathroom, you shouldn't get a lot of vapor out into the hallway.

Also - is the battery backup a requirement by NEC code? Or is that requirement more a municipal thing that varies from place to place?
Municipal building code, but I believe that's a fairly universal requirement.
 
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Old 08-26-08, 06:55 PM
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Basically the IRC points you to NFPA 72:

R313.1 Smoke detection and notification. All smoke alarms shall be listed in accordance with UL 217 and installed in accordance with the provisions of this code and the household fire warning equipment provisions of NFPA 72.
Household fire alarm systems installed in accordance with NFPA 72 that include smoke alarms, or a combination of smoke detector and audible notification device installed as required by this section for smoke alarms, shall be permitted. The household fire alarm system shall provide the same level of smoke detection and alarm as required by this section for smoke alarms in the event the fire alarm panel is removed or the system is not connected to a central station.

Then adds:

R313.2 Location.
Smoke alarms shall be installed in the following locations:
1. In each sleeping room.
2. Outside each separate sleeping area in the immediate vicinity of the bedrooms.
3. On each additional story of the dwelling, including basements but not including crawl spaces and uninhabitable attics. In dwellings or dwelling units with split levels and without an intervening door between the adjacent levels, a smoke alarm installed on the upper level shall suffice for the adjacent lower level provided that the lower level is less than one full story below the upper level.
When more than one smoke alarm is required to be installed within an individual dwelling unit the alarm devices shall be interconnected in such a manner that the actuation of one alarm will activate all of the alarms in the individual unit...

and

R313.3 Power source.
In new construction, the required smoke alarms shall receive their primary power from the building wiring when such wiring is served from a commercial source, and when primary power is interrupted, shall receive power from a battery. Wiring shall be permanent and without a disconnecting switch other than those required for overcurrent protection. Smoke alarms shall be permitted to be battery operated when installed in buildings without commercial power or in buildings that undergo alterations, repairs or additions regulated by Section R313.2.1.

Local codes may require a higher level of protection, but they cannot specify less protection than required by the IRC and NFPA 72.
 
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Old 08-26-08, 07:51 PM
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Thanks for all the tips - all helpful.

I spoke with a couple electricians today who suggested possibly putting the detector just outside the tiny hallway - they mentioned being within 15' of the BR doors as probably being ok per local inspectors. BUT it could depend on the specific individual doing the inspection.

So - it's something I'll check out with my building dept.
 
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Old 08-28-08, 03:50 PM
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Within the BR's what is the typical spot to locate the detector on the ceiling? My detector's instructions suggest the center of the room, but with an overhead light I wouldn't think getting very close to that would look good.

Is midway between the center and the door a good option?

What's typical?
 
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Old 08-28-08, 04:49 PM
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you need a photoelectric in the kitchen. You need a carbon monoxide detector on each floor in the common area of each floor typically in the center of the common area including the basement, you need a ionization detectors in each bedroom i would say about 3 feet away from the door swing. and you need a detector at the top and bottom of each set of stairs within about 5 feet from the landing. if the common areas are close to the stair ways i think its about 20 feet or so then you are allowed for only one to cover both. and if you have a garage i believe you need a heat detector out there. i will check the nfpa 72 book later and if i am wrong on anything i will write another post correcting myself.
 
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Old 08-28-08, 05:03 PM
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Chewy,

Are you posting the State of Mass. local rules? What you seem to have posted seems stricter than what I am more familiar with, especially the part requiring CO detectors on each floor.

Please clarify your source. Please remember that different locales can have local adoptions. Questions here are generally answered based on National codes or standards.
 
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Old 08-28-08, 05:11 PM
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Originally Posted by chewylu103 View Post
you need a photoelectric in the kitchen. You need a carbon monoxide detector on each floor in the common area of each floor typically in the center of the common area including the basement, you need a ionization detectors in each bedroom i would say about 3 feet away from the door swing. and you need a detector at the top and bottom of each set of stairs within about 5 feet from the landing. if the common areas are close to the stair ways i think its about 20 feet or so then you are allowed for only one to cover both. and if you have a garage i believe you need a heat detector out there. i will check the nfpa 72 book later and if i am wrong on anything i will write another post correcting myself.
All of the above doesn't really apply to my local codes. We require 1 in each BR, 1 outside them within about 15' of them, then only 1 per house level including basement. I'm thinking of using dual sensor units, but definitely don't want one anywhere near the kitchen. In fact everything I read online and by manufacturer instructions warns against that due to so many false alarms.

My question really was geared to the bedrooms - what's the typical placement in there?
 
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Old 08-28-08, 05:35 PM
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photoelectric is designed for a delayed response for exactly what you fear a false alarm thats why its not the typical ionization but i was also just covering all the basis' i did include the footage on the bedroom smokes so go by that whenever i wire a house thats the way i do it and the inspector likes it it wouldnt hurt to have a carbon monoxide on each floor whats the harm in making sure your kids/family are all right. pick what you need from what i wrote and use it thats all.
 
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Old 08-28-08, 05:54 PM
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I try to keep them within about 3-4 foot of the bedroom door, but no hard and fast rule. Try to plan how it will look in the room.

Do keep the alarms at least 3 foot away from ceiling fans and HVAC vents or returns. This is covered in the installation instructions. Also avoid the "dead air" spaces shown on the diagrams.
 
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