CO/Smoke Detectors
 

My Kidde "CO" (Carbon Monixide) detector died today. I found out that these detectors (Smoke Detectors Included) have a UNIT Shelf life. This means the UNIT detector...which has a small radioactive (nuclear) element in it will die at about seven years of service. My UNIT went for eight years.

I NOW (Today) have a NEW UNIT which is almost identical to the old one except it Now can detect Flammable GAS as well as CO. (New Software)

It will also tell you when it has OUTLIVED it's usefullness...BY displaying "END"..on the display.... Essentially saying ..I AM DEAD Replace Me.

Bottom Line: These detectors have a Life Span..erepective of just changing the battery's. :look: NB

Most manufacturers say the life span for a smoke detector is 10 years. A smoke/CO combo detector is 5 years.
I like the device having an indicator stating that it needs to be replaced. To often I see detectors that are beyond yellowing and the are still in service.
It's smart of you to replace them, many people don't, I myself need too.

Shelf life
 

I notice many smoke detectors still in use after 10 years when in fact they are no longer useful. You would think the manufacturers would want the depectors to display the end of their usefullness so that they can sell another unit?

Live and Learn...
 

I bought a CO detector about 20 years ago for $32. When the detector signaled that it needed attention, I replaced the standard 9-volt battery. In addition, the detector's instructions directed the purchaser to replace "The Module"—from the manufacturer—at $40!

I yanked "The Module" out, and pried open its seal: inside was a second standard 9-volt battery.

:eek2:

Location for a smoke or carbon monoxide detector? Does it make all that much difference that it gets installed up on the ceiling, or over on a vertical wall, about one foot down from the ceiling? What is the difference?

...with a shower installed...
 

Don't place a smoke detector above any bathroom door...!

:look:

Co detector never up high
 

FLL

Never install the Co detector up high, ceiling. Co is heavy and settles in low areas. These detectors should be installed BELOW your head level on the bed. That way it will sound before the Co gets to you. If you have a cellar with "no" sleeping area then it can be installed higher as Co will fill the cellar before it reaches the living area.

I have a smoke/Co detector in the hallway of the living area installed on a wall outlet. Not so good for smoke as smoke will be up higher. So I also have smoke detectors in the hallway mounted on the ceiling. I have three smoke detectors in the house as well in areas where they can detect smoke before it gets into bedrooms.

Just remember the combination detectors can't really do both well. They are a compromise between each detection for convenience of the user. So I suggest to use both smoke/Co and pure smoke detectors in combination to get the full benefit.

The question then becomes a cost question. My answer is "what is your and your families life worth?"

ToW

If it's a smoke detector or a combo CO/SMOKE it has to be installed on the ceiling. A CO detector can be mounted anywhere at any height as the CO is about the same weight as air.
I'm not sure about the fire codes for placement in your town (10 ft. within any bedroom, 1 on every floor, photoelectric or ionization, etc.)

Installation varies by the manufacturer, but CO is not heavy. It's slightly lighter than air. If anything it may be contained higher up in the room in warmer air coming from combustion appliances like heating equipment. If the CO mixes with the warmer air it can and will rise with it.
Propane is a heavy gas that will sink low and find pockets.
I'd just follow the manufacturers recommended placement.
I do agree with ToW about paying a bit more and not using the combos.

CO is definately not heavier but in fact slightly than the air we breath.the difference is so small (maybe 8%) that most likely it will mix in all levels if even small air movement is present.I looked at First Response detecters and their manual does not specify mounting height,just location.

Just to quantify things, the molecular weights of nitrogen, oxygen, of the blend we call "air," carbon monoxide, and pure propane are:

N2 28.014
O2 31.999
air 28.951
CO 28.010
C3H8 44.097

So, CO is almost exactly the same weight as nitrogen, and one can conclude that molecular diffusion keeps the molecules well mixed, without stratification. Propane is sufficiently heavier that it can stratify, although given time it will diffuse into the bulk air.

Replacing
 

All I know is with a house ten years old and the wired in smoke detectors on their last legs, it is an expensive proposition to buy all new ones. I understand that we need them but things are very tight right now. It just never ends does it?

I think ToW is thinking about CO2 (carbon dioxide), which is heavier than air. There are lots of stories about dry ice fumes pooling up and causing lack of oxygen.

CO is carbon monoxide and it comes from burning stuff. House furnaces and engine exhaust are the most common sources of CO danger. Being a weekend boat resident, we always hear the stories about boaters killed by CO. I keep my CO detector near my head since that's where I breath.

GsChinadoll This comment really sums up the baisis for many desicions. Just saying.
Oh, and sorry to 2nd you but, no it doesn't end.............. :)

Ten years is a manufacturers recomended life of a "smoke" detector to be with in what they consider its average reliable range. What the device is exposed to can change this considerably.(dust, cooking fumes, being dropped when changing the battery, ect..) It won't stop working in ten years, but alot can happen in that time frame jeopardising its calibration.

I know you don't want this answer....the paperwork that comes with it should explain where to install that specific device. A quick conversation with your Town Electrical Inspector should help. PaugusBayFireFighter has given good advice also. You could stop into your local Fire Dept and ask the question there too, people in general are always up to help someone trying to do the right thing.
I feel its best to mount the device on the ceiling. In a situation that doesn't allow access to the space above, the wall IS an option, the device needs to be within a foot of the ceiling in that case according to the devices install instructions. You want the device positioned so smoke reaches it fast, taking into consideration sloped and vaulted ceilings, ect.. In a large room, if a fire started near the opposite end you wouldn't want the detector a foot below the ceiling "x" number of feet away at the other end, you want it ceiling mounted in the center of the room for coverage.

I know when building a new house in NH smokes need to be hardwired in every bedroom and you need a C/O on every level of the home. When mounting a C/O in the basement make sure it not to close to the furnace, it might be a PIA and go off every time the furnace starts I found that one out the hard way.:D

Codes
 

Codes varies from town to town. Laconia requires a smoke detector on every floor preferably in the hallway. I have rental property in Hooksett. The Hooksett codes requires a smoke detector in the Bedroom hallway, a heat detector in the Kitchen area. If you have gas applinces, A CO detector should be located near the floor where the appliance. If you have a cellar the CO detector should be located in the cellar. Hooksett requires hard wiring.
As for rental property HUD federal requiements is a smoke detector on all floors including cellar if you have one. The federal requirements almost always contrdict local codes.

Call your fire dept for code requrements. They will even come inspect your house as to proper placement.

I hope that you have better luck than I - with a combo unit.

Went to store few years ago and purchase 3 brand name combo units. Hard wired units with backup battery.

All within three years malfunctioned. No way to stop the beeping. On all. Multiple new batteries of different brands and stores. No it was not one bad batch of batteries from a single store.

Changed tactics. Replaced all with standard hard wired smoke alarm. Then purchased separate carbon detectors that work by battery. No beeps since.

Not sure on this, but one bad device may have sent a pulse causing the other two to also chirp if they were interconnected. Many devices say in the instructions to push the test button after changing the batteries. Its also very important to check and make sure the devices are compatible with each other. Most seem to be but not always! Glad to hear you installed devices where the defective units were and not just disconnect them.

Depends on the house.
 

The reason I spoke the way I did, Co "about" the same weight as air is true. "But" We had a home here in town that had electric heat. Very little air movement other that normal air currents. The time was late spring so the heat was not on so no convection to mix the air. They had a gas fireplace malfunction at the flue. It was on a lower level of the house.

The Co/smoke detector was on the ceiling outside the bedroom. When the folks were found the alarm was screaming but the folks were unconscious. What happened was the house slowly filled with Co and they were overcome before the detector sounded.

Goos news is that all survived!! Another family member had stopped by and found them before it was to late. Thank God.

The fire investigators found the detector worked as designed but due to the "slow" accumulation of Co it did not detect the gas on time to alert the family. Hence my and the Chief's feeling that they should be separate detectors and located as I wrote about.

But again it's each persons choice. I chose to go the expensive route.

ToW

When CO detectors started being required we were chasing alarms all day and night. The first detectors were over sensitive and home owners were calling us out often. As the years have gone on we have much less frequent calls for CO alarms. The ones we do get are sometimes legitimate alarms (our gas monitors confirm the presence of CO and other gasses), but mostly malfunction or battery issues. They are definitely life savers and worth the cost.
Tasteless, odorless, colorless....

NEST Protect / Installers?
 

Has anyone had experience with the NEST Protect smoke/CO detectors? Previously, there was only a battery-operated model available, but there is now a wired model, which would seem to meet code requirements (e.g., Meredith).

In the same vein, does anyone know local installers who have worked with the NEST Protect products?

Any advice/information will be appreciated.

Combination smoke/CO detectors
 

When you get a smoke detector, instruction tells you to mount on or near the ceiling. When you get a CO detector, instruction tells you to mount at the lowest floor near the floor.

I looked at a combination smoke/CO detector and notice the instruction tells me the unit should be installed near the ceiling. OK how does the CO portion works if CO is heavier than air?

I think combination detectors are a marketing gimmick and serves no real protection. Anyone wants to comment?

Nest Protect Units
 

The density of CO is slightly less than air, AND common sources of domestic CO also generate warm air. For both of these reasons, CO accumulates at high points and fills living spaces from the top down.

I have two battery-operated Nest Protect units, both on interior walls five feet above the floor.

I also have eight wired smoke alarms on various ceilings, so if you are doing a new install, I would probably place the Nests on the ceilings.

Face palm :look:

You can put a CO detector at any level of a room because the diffusion of carbon monoxide in air is relatively even. Smokes are always at the highest point in the home. Combos would always be mounted at the highest point of a ceiling. Wall mounted go no less than a foot from the ceiling.

Both CO and nitrogen are molecular weight 28; oxygen is 32. The weighted average for air is 29. CO will be distributed fairly well throughout the room by molecular diffusion alone. If the molecules stratified by molecular weight difference, we'd have oxygen down low and nitrogen high, and you'd be asphyxiated just by standing up. Thermal currents due to air rising at interior walls and sinking by cold exterior walls helps the mixing.

However, as was said above, smoke and CO are produced by incomplete combustion, and sources usually involve fire or some other heat source, and both these pollutants tend to be transported upward by thermal convection initially. Early detection is important, so a high mount usually is best, although one could argue that optimum placement really depends on the configuration of a particular house or room and where any smoke or CO most likely would be introduced.