Thread: Smoke alarm placement

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Dan
Perhaps this will help?

From NFPA 101 (NFPA 72 references NFPA 101 for locations):
- 24.3.4 Detection, Alarm, and Communications Systems.

Approved, single-station smoke alarms shall be installed in accordance with 9.6.2.10 in the following locations:

- - (1) All sleeping rooms

- - - Exception: Smoke alarms shall not be required in sleeping rooms in existing one- and two-family dwellings.
- - (2) Outside of each separate sleeping area, in the immediate vicinity of the sleeping rooms
- - (3) On each level of the dwelling unit, including basements
- - Exception No. 1: Dwelling units protected by an approved smoke detection system in accordance with Section 9.6 and equipped with an approved means of occupant notification.
- - Exception No. 2: In existing one- and two-family
dwellings approved smoke alarms powered by batteries shall be permitted.

That archway separates the two areas - the hall for the bedrooms from the living room, making it *not* 'in the immediate vicinity of' the bedrooms, thus, the smoke alarm needs to be on the bedroom side of the arch (the other smoke alarm may be left where it is, or it could be relocated).

At least that's the way I read it and the way all inspectors (code inspectors) I know read it. Now, if that arch was not there, and the smoke detector was on the living room ceiling *at* the entrance to the hall, and the hall is only 5 feet long, an argument could be made that it was still 'in the immediate vicinity of' the bedrooms. The hall is only 5 feet long and the door is 2 feet+ wide, meaning there is only 3 feet or less of wall before the entrance to the bedroom - that's pretty close ... but when you throw that archway into the picture, the picture changes ...

I recall that if there's a header, arch, or beam 24" or more in depth projecting from the hallway ceiling between the location of the smoke alarm and the bedroom entry door another SA is needed. I will need to research this to find confirmation unless Jerry P has it up his rather large code coat sleeve?

Jerry Mc.,

Does not mention projections in NFPA 72 or NFPA 101, just locations, however, *any* "projection" downward would create a dam effect and create a serious time delay for smoke travel as the smoke would need to build up enough to then pass under the projection.

A similar effect would be if the hall ceiling had a tray ceiling - the smoke would accumulate at the higher portion, thus, that is where the smoke alarm should be (is required to be), not on the lower flat part of the tray ceiling (same for smoke alarms in bedrooms with tray ceilings or slope ceilings - the smoke alarm needs to be at the higher point (except for a peak, then the smoke alarm needs to be 'near', but not 'at' the peak, down at least 4" and within (I think it is) where the two slopes are 6' apart as they slope away from each other, which puts the smoke alarms within 3' of the sloping ceiling ... plus smoke alarms at the 1/6 points in from the walls.

Jerry Mc.,

This is probably what you are thinking about:

From NFPA 72: Note the "heat detectors"

"A-2-2.4.3 The location and spacing of heat detectors should consider beam depth, ceiling height, beam spacing, and fire size.

- If the ratio of beam depth (D) to ceiling height (H), (D/H), is greater than 0.10 and the ratio of beam spacing (W) to ceiling height (H), (W/H), is greater than 0.40, heat detectors should be located in each beam pocket.

- If either the ratio of beam depth to ceiling height (D/H) is less than 0.10 or the ratio of beam spacing to ceiling height (W/H) is less than 0.40, heat detectors should be installed on the bottom of the beams.

And one more with some drawings from Appendix A to NFPA 72.

I'm not sure that I would (as a home inspector) start writing up to the sloped ceiling one, though, for one and two family, not even sure I would for the peaked ceiling one either.

I'd want to do some more reading to make sure that was the intent (even though it sure looks that way - this is, after all, from the Appendix A to the NFPA 72, "Appendix A Explanatory Material", "Appendix A is not a part of the requirements of this NFPA document but is included for informational purposes only. This appendix contains explanatory material, numbered to correspond with the applicable text paragraphs."

Originally Posted by Jerry Peck

From NFPA 72: Note the "heat detectors"

"A-2-2.4.3 The location and spacing of heat detectors should consider beam depth, ceiling height, beam spacing, and fire size.
- If the ratio of beam depth (D) to ceiling height (H), (D/H), is greater than 0.10 and the ratio of beam spacing (W) to ceiling height (H), (W/H), is greater than 0.40, heat detectors should be located in each beam pocket.

Example: 8 foot ceiling:

Ceiling height = 96"
Beam depth .25" (2x10)
9.25 / 96 = 0.096 (which is just barely less than 0.10)

AND

Ceiling height = 96"
Beam spacing = 38" between beams
38 / 96 = 0.395 (which is just barely less than 0.40)

Appears as though the above would make it. But, how many times do you find them spaced with 38" between beams? More likely, as in the question at hand, there is an end wall (which would act like a deep beam), a 5 foot long hall, then the arch beam. That would make the beam spacing/ceiling height calculation change to 60 / 96 = 0.625, which would exceed the 0.40 limit.

BUT ... there is that "and" in there, so, how deep is that end beam (arch)?

Okay, the below has an "either" and an "or" in place of the "and".

- If either the ratio of beam depth to ceiling height (D/H) is less than 0.10 or the ratio of beam spacing to ceiling height (W/H) is less than 0.40, heat detectors should be installed on the bottom of the beams.
[/quote]

Now, it does not matter what the depth of the beam is (unless it fits the first "and" calculation.

The location of the heat detectors depend on the "either / or" or the "and".

Jerry Mc,

Take cover He's started pulling out Appendixes.

Billy, codes are like spy novels and can become very tricky in the eye of the beholder. Serve on a code interpretation committee and you will soon see what I mean.
Back to the subject at hand and here's the California version:
CBC 2001: Smoke Alarms – Sec. 310.9.1.4, Location within dwelling units. In dwelling units, a smoke alarm shall be installed in each sleeping room and at a point centrally located in the corridor or area giving access to each separate sleeping area. When the dwelling unit has more than one story and in dwellings with basements, a smoke alarm shall be installed on each story and in the basement. In dwelling units where a story or basement is split into two or more levels, the smoke alarm shall be installed on the upper level, except that when the lower level contains a sleeping area, a smoke alarm shall be installed on each level. When sleeping rooms are on an upper level, the smoke alarms shall be placed at the ceiling of the upper level in close proximity to the stairway. In dwelling units where the ceiling height of a room open to the hallway serving the bedrooms exceeds that of a hallway by 24 inches or more, smoke alarms shall be installed in the hallway and in the adjacent room. Smoke alarms shall sound an alarm audible in all sleeping areas of the dwelling unit in which they are located.

Originally Posted by Jerry McCarthy

In dwelling units where the ceiling height of a room open to the hallway serving the bedrooms exceeds that of a hallway by 24 inches or more, smoke alarms shall be installed in the hallway and in the adjacent room.

Jerry Mc.,

Okay, I have not seen anything like that, but that is not referring to 'beams'.

If the hallway ceiling is 8' and the living room ceiling (just for an example) if greater than 10', then a smoke alarm also needs to be installed in the living room.

But ...

What about where the hallway ceiling is 10', the living room ceiling is 10', and there is an arch separating the two which is 8' at its high point?



By the way, thanks for the CA code, it is interesting to read different codes regarding the same thing.

EC Jerry
I read the CBC to mean any projection from the ceiling located in a hallway serving sleeping rooms 24” or more in depth would require a separate smoke alarms on each side of the projection. You alluded to smoke volume build-up having to increase until it was thick enough to enter an area that has a smoke alarm installed in it with which I concur. Even though I called it “hallway” I mean any area outside of a sleeping room where a coffered ceiling could trap smoke preventing it from reaching and setting off an alarm presents a hazard to occupants and should be so reported.
WC Jerry

For those that may not know what a coffered ceiling is - see photo.

I am not a code inspector so I am free to advise my clients on what I feel is safe. I personally recommend to my clients a smoke detector in each bedroom. Some people do sleep with the door closed. As a retired firefighter I know fires do start in bedrooms also. Whenever I give advice on smoke detectors I mention to follow the manufacturers instructions for placement and maintenance. I agree with your assessment, smoke detectors are placed on ceilings because smoke rises with the heat from a fire and any thing that would impede the spread of smoke such as an archway will delay the alarm. If you can give sound reasoning for your recommendation I don’t think you can be faulted. What is the cost of a smoke detector today anyway?

David
I don't know of any home inspectors who claim to be code inspectors, but I do know that all home inspectors inspect to the code that's in effect at the time of inspection. In all due respect the building codes are our road maps and without adequate code knowledge one can easily step into the snare of a person with "Esquire" after their name by missing a non-code complying issue, especially one that effects occupant safety.
I don't mean to lecture or pick on you David, but this business about building codes, knowing them, not knowing them, or not inspecting to them has always aroused my ire.

Jerry

I am not down playing that a good knowledge of codes is important, I worked with the codes doing inspections as a firefighter especialy the ones pertaining to egress and occupancy. After reading bulliten boards for many years I get the impression that many inspectors will not make a recommendation unless it is based in code and that many even will cite codes. In this neck of the woods we have been counseled that if you cite code for one thing in a report in effect you commiting yourself to inspect the entire building to code incluging pluming and electrical. Most certainly if you are going to do new home acceptance inspections or phase inspections you had better know the codes that apply. I am not saying either that we can go around just dreaming up our version of the way things should be but sometimes a little common sense goes a long way.

By the way I though you were quite polite, no need to apologise

David

Originally Posted by David J. Smith

In this neck of the woods we have been counseled that if you cite code for one thing in a report in effect you commiting yourself to inspect the entire building to code incluging pluming and electrical.

David,

(From the other Jerry)

That is one of the problems many home inspectors face today - their training give them false information and it then becomes 'home inspector myth' and is passed on as 'truth'.

In fact, if that were so, if you mentioned *one* "safety item", you would have to mention *every* "safety item".

Or, if you mentioned "one" "health hazard", you would have to mention *every* "health hazard".

Obviously, one person cannot know about "every" "safety, health, code, etc., regulation or requirement", thus, the home inspector is charged with learning as much as they can, then inspecting and reporting based on their knowledge base.

Be it code, heath, safety, or whatever.

The simple fact of the matter is, though, that structures (which home inspectors inspect) *are* "built to code" (supposedly, anyway - we all know differently ) making the knowledge of code a "requirement" for the home inspector.

Otherwise, how is the home inspector to determine whether or not something is good or not good and what to write up?

Thus, whether home inspectors like it or not, or admit it or not, they are 'inspecting for code' ... notice, I did not say 'inspecting TO code' but 'FOR code'.

Why do you inspect for GFCI protection? Code? Safety? Does that now mean you must write up *ALL* code or safety items? Of course not. BUT ... GFCI protection *IS* "code", as is almost everything else.

East Coast Jerry

Agree with all the above.

I have never professed to know everything about property inspecting and I’m more than positive that there are many out there who can run circles around me both in ability and knowledge. However, I am a firm believer in the following, which has come about mainly through what I have learned conducting property inspections, teaching, and performing expert witness work related to the real estate inspection profession.
1. Every property inspection requires a performance.
2. Every performance requires a certain degree of skill.
3. One will never know enough about every component or system in a residential dwelling.
4. One will never have an adequate knowledge of all of the building codes.
5. Every inspection performed is based on building codes.
6. All good inspectors are also good detectives.
7. Inspection skill requires knowledge, but also a very high degree of awareness.
8. Knowledge of one’s craft is a major requirement, but so is the skill in communicating what one observes.
9. Being sued is not an if; it’s a when.
10. Your defense will be based on both the knowledge of your craft and your communication* skills.

* Communication; verbal presentations and written reports.