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Household smoke alarms

mueller

mueller

Bronze Member
Joined
Oct 17, 2009
Messages
57
Household smoke alarms

Photoelectric VS. ionizing VS. duel ?

I was recently asked to make a recommendation as to which type of alarm would be

best to replace existing fully compliant 10 year old alarms in a SFD.

I normally wouldn't touch this for liability reasons but it came from a family member.

I'm in NJ which does not regulate this other than IRC and NFPA 72.

I saw a proposal at the code hearings to ban the ionizing units.

I also see Massachusetts, Iowa and Vermont have adopted regulations that seem to be

leaning away from the ionizing only units.

My conclusion is to recommend duel alarms throughout with the exception of any alarm

near cooking to be photoelectric only. BRK has a photo unit compatable with there duel

alarm in fact they have the only duel alarm I can find that hasen't been recalled.

Just wondering what you all do in your own homes or what your AHJ'S have adopted ?
 
Re: Household smoke alarms

The debate has gone on for far too long and has confused far too many professionals. Personally, I don’t like seeing any jurisdiction take such a stance as prohibiting any one particular type since they are designed to perform on different fire signature scenarios based on their operational technology.

Professionally, we should recommend using a combination protection scheme using both types of detectors. Based on the many research reports I’ve studied for many years including an independent study related to tenability issues for smoldering and flaming fires using all three types (photoelectric, ionization and combination); I maintain my professional opinion that we should recommend using both types.

Smoldering fires where photoelectric is typically better suited do not produce untenable carbon monoxide levels as fast as flaming fires do where ionization are better suited. In addition to the lacking levels of CO produced in the smoldering fire, the heat levels are also lower versus a flaming fire scenario.

(Source: MFIS Conference Presentation on Full Scale Testing “Smoke Alarm Technologies: Performance and Forensic Analysis, September 2009 - Daniel Gottuk, Ph.D., P.E.) dgottuk@haifire.com

Basically, people die from CO and heat and these products of combustion are more prevalent in flaming fires hence ......... people need early warning in flaming fire scenarios before the dwelling environment becomes untenable.

BTW.......I have both types in my home and always have :D
 
Re: Household smoke alarms

Have the ' CO2 type ' and the ' heat sensing types ' caught on in any jurisdiction out there?

 
Re: Household smoke alarms

I'd advise against the dual system.

UL has conducted a series of tests and what they found was a bit surprising. Depending on the fire type either a photo or ion detector activated first. The argument for the photo was that the typical fire is smoky as it starts and the types of by-products are detected earlier with the photo detector than with the ion one.

The surprise was that the time to activation was longest with the dual detectors. The delay is not significant - similar to the difference between photo and ion devices - but the dual units were consistently longer in activation than either one alone. The reason is that they don't act on the first instance - they act by comparing notes (so to speak) and only activate when there is conclusive evidence that there is smoke from a fire.

There is less likelihood that a dual detector will activate from burnt toast but is that worth the delay?
 
Re: Household smoke alarms

Agree with Gene too!

NorthStar: Jury still out on those CO-Smoke-Heat-Steam. Cda had something on the old ICC BB and you may want to PM him/her for further details.
 
Re: Household smoke alarms

Y'all are making me rethink this a bit.

I am now tempted to buy a full set of each type and install them side by side at every location!

As my house is now a little over 11 years old, it's getting to be about time to consider replacement anyway... 8 locations - 1 each bedroom (4), one in hall upstairs, one in hall downstairs (2), one in basement rec room and one in boiler room (2).

Anybody got $150.00 I can borrow? (not forgetting CO by the way, but it's a plug in unit only about 7 y.o....). Maybe combos? Make it $200.00...

These are the days that being a Procrastinator comes in handy... :roll:
 
Re: Household smoke alarms

btw: CO detectors should NEVER be combination smoke/heat. Carbon Monoxide is heavier than air and sinks. CO detectors should be located lower on the walls. The make CO detectors that plug into electrical outlets, which, it turns out, is almost exactly the right height.

And don't assume that if you put one in the basement you're OK. If there is a source of CO in the basement, teh air handler will pick it up and distribute it throughout the house, diluting it along the way. So, the CO in the basement family room may actually be less than what gets to the living room or bedroom on the main floor. :geek:
 
Re: Household smoke alarms

Gene - Is CO heavier? I always thought it was (hence the plug-in units), but was told a couple of years ago that it wasn't... :? I haven't taken the time to research it for my own piece of mind... the down side of procrastination... :eek: Never did trust that lighter-than-air idea. :roll: But it IS one component of 'air', so I did give it a bit of credence (basically just enough to keep me thinking about it).

My primary heat is oil-fired hydronic, and the only other source is my LPG stove/oven (we never use the gas log fireplace... it gives off a foul odor), so it's not a huge deal for me. The BRs are all upstairs and fuel fireds are all below. Our CO detector is a plug-in in the hallway on the bedroom level. With the boiler room door closed there is very little air transfer into the house, and I usually use the exhaust fan (duct to the exterior) when using the oven and frequently when using the stove.

The dogs sleep in the laundry room directly above the boiler room, and I kind of figured if it WAS lighter and there was a problem the dogs would always be sick from it. Since they're not, EITHER there is no problem or the stuff is heavier than air... :?:
 
Re: Household smoke alarms

mtlog - Actually had a case involving an unvented LPG furnace (it was SUPPOSED to be vented...) where the tenants dog had been sick since the start of heating season.

I was at the property for a different building, but as a matter of course we looked at all units as the landlord had done some unsavory (read as dangerous) installations.

The woman was reluctant to leave as she didn't think there was problem. She only spent a few hours per day at home and said she felt fine, but the dog was inside almost all the time. When I asked if the dog had unusual symptoms, she told me he had been vomitting frequently, was listless, etc. I told her to have the veterinarian do a blood test for CO poisoning.

Never heard back from her, but she did relocate after that night!
 
Re: Household smoke alarms

Carbon Monoxide specific gravity is actually lighter than air (0.9667) where air's SG = 1. CO can mix with air in the dwelling at various levels and as Gene references it can be distributed through air distribution equipment.

The key is the time factor in exposure. This is why CO detectors measure levels of CO over time and alarm before an "average healthy" adult would experience symptoms (as designed). UL 2034 lists detectors/alarms to function at 100 ppm/90 min; 200 ppm/35 min and 400 ppm/15 min.

Bottom line is that if one is installing Smoke or CO detectors in the home; use a combination approach using Photoelectric, Ionization and if you are only installing one CO, install it outside the bedrooms.
 
Re: Household smoke alarms

Thanks for the responses

Of course I already ordered the units for my fathers 2 bed ranch.

I went with 2 duel sensing for the bedrooms , 1 photo for the hallway and 1 plug in CO.

All was well untill I read gene's post. Thanks Gene now I,m rethinking this again.

JD- I briefly thought about 1 of each at each location as you mentioned. That's how I arrived at the duel sensing units. Unless you have a friend selling smokes you will need more than $200.

Loew sells the photos for 25, ion for 15 and 40 for the CO. All the instructions that I read limit the number of smokes to 12 plus 6 accessory units so you can't do that anyway. Perhaps alternating ion / photo is the way to go.
 
Re: Household smoke alarms

"Carbon Monoxide specific gravity is actually lighter than air (0.9667) where air's SG = 1. CO can mix with air in the dwelling at various levels and as Gene references it can be distributed through air distribution equipment. " (F M W B)

The difference in specific gravity is almost negligible... so they probably mix readily and just walking around would be enough to dilute the CO into the air (or putrify the air, depending on viewpoint).

This one is not easy.
 
Re: Household smoke alarms

Thanks JD I’m touched :lol: . I agree with the negligible gravity level just wanted to state the scientific substantiation, It doesn't have to be complicated......as you know, get three professionals in a room and none will agree. (hence confusing professionals in my original reply)

All specifications and technical data I’ve read over the years on CO detectors are to install them on every level away from fuel sources and typically at ceiling levels. Regardless as to where one installs a CO detector the important thing is that one installs them (time v. exposure). Regarding the standard smoke detector/alarm; using a duel detector approach is typically recommended.
 
Re: Household smoke alarms

An investigative journalist with WTHR in Indiana looked into this issue after some tragedies in their area; the report is titled Deadly Delay.

We do have hardwired and interconnected ionization and photoelectric smoke alarms.

As for CO, it is a common product of combustion that would be expected to be present in the smoke produced by a fire. While the device may be looking for CO independently, it could also be seeking to limit nuisance alarms if increased CO levels are not present.
 
Re: Household smoke alarms

"Thanks JD I’m touched . I agree with the negligible gravity level just wanted to state the scientific substantiation, It doesn't have to be complicated......as you know, get three professionals in a room and none will agree. (hence confusing professionals in my original reply) "

I have aleays heard that if you get two inspectors together it will result in three opinions!
 
Re: Household smoke alarms

Gene Boecker said:
Carbon Monoxide is heavier than air and sinks. CO detectors should be located lower on the walls. The make CO detectors that plug into electrical outlets, which, it turns out, is almost exactly the right height.
Click to expand...
Carbon monoxide is not heavier than air. I hear this a lot and I wonder if it is because people are confusing carbon monoxide with carbon dioxide which is heavier than air. Carbon monoxide is slightly lighter than air. Searching on the web will yield numerous references for this, but here is a useful one http://www.engineeringtoolbox.com/specific-gravities-gases-d_334.html.
 
Re: Household smoke alarms

EPrice said:
Gene Boecker said:
Carbon Monoxide is heavier than air and sinks. CO detectors should be located lower on the walls. The make CO detectors that plug into electrical outlets, which, it turns out, is almost exactly the right height.
Click to expand...
Click to expand...
Carbon monoxide is not heavier than air. I hear this a lot and I wonder if it is because people are confusing carbon monoxide with carbon dioxide which is heavier than air. Carbon monoxide is slightly lighter than air. Searching on the web will yield numerous references for this, but here is a useful one http://www.engineeringtoolbox.com/specific-gravities-gases-d_334.html.

I see a lot of plans stating CO2 instead of CO, and a lot with the detector in the mechanical room.
 
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