Replace Your Old CO Detector!!

The sensor doesn't absorb CO and retain it. The CO molecules diffuse into the sensor element and change the electrolyte solution's conductivity. This change is what the electronics measure. When the air is cleared of CO, the CO that had diffused into the sensor, re-deffuses into the surrounding air. The sensor fails when the electrolyte evaporates. See National Semiconductor application note AN-1798 for more details. http://www.national.com/an/AN/AN-1798.pdf

Not trying to recommend anyone using a old CO detector . I have 3 new detectors and 1 that is 9 yrs old .When the weather was warm the other day at lunch time my wife came home they were all going off . The 9yr old and new had close to the same reading on the display . So they may still be good for a room that is not normally monitored . Dave

That's a good idea, Flyer. Get the new ones for the key areas of the house like the bed rooms and stove room, then add the old ones to the garage, etc.

Beats just chuckin them.

Mass. fire regulations say replace CO detectors after 5 years. In our city, smoke detectors are required to be replaced after 10 years. The manufacturers have recommendations in their enclosed literature as well.

You might not be in as much trouble as you think.
My mechanic told me that newer engines don't produce CO like the old ones.

My CO detector jumper to life when placed it several inches from my (outside)idling Wheel Horse 14hp single lung Kohler, Wow!!

My 5 year old detector went off at 12.30 am last night. I opened the windows and moved it to my bedroom. It then went off at 1.30 a.m.

My coal stove hasn't even been turned on yet. Still burning wood and just burning fuel oil for hot water.

It needs to be replaced. Going to get a new unit with digital read out today.

Here is a new press release from New York State about smoke detectors. Stay safe change your batteries
Chris H

One of the most important items in that press release is #4. Replace smoke detectors older than 10 years. Just because a detector beeps when you push the button doesn't mean it will detect smoke. It only means the beeper works and there is a power supply. The sensors have about 2 microcuries of americium-241, a radioactive element in them that gets weak over time. The sensors are then unrelieable. The damn things are so cheap, it's not worth taking any chances.

just want to put my 2 cents in. I have 2 co detectors , one is brand new w/stove (koker) and one from 6 years ago. My wife called me at work in the afternoon to tell me the older one is going off, thought maybe a fluke because new one wasn't going off. opened windows because it was a nice day anyway (60*+). As the day went on we took the batteries out of the old one. Well come 3am new detect. went off thats when panic set in. turns out there was a build up of ash at the top of the furnace where the two exhaust pipes meet. Those with kokers may know what I mean. Still had good draft but co was backing up though the door. Moral of the story is the old co detector warned us well before the new one did I just thought it was going bad! Thank the lord for CO detectors. It will save you and your precious families lives it saved mine!!!!!! If you burn coal and you dont have a CO detector you should just pull the trigger

mark.

Just a CO monitor experience to share. Don't use those sprayon sunscreens near them. We had one go crazy when we sprayed the kids near it. Had to leave it outside a couple days to clear it out. Makes you wonder whats in those cans.

Well let me give you my method and introduce a little controversy. I am new to coal but not new to chemistry. this is my issue. As pointed out in this thread many people for whatever reason are relying on CO detectors that are not giving them the safety they wish for. A little background:

Carbon monoxide has nearly the same density as air.
You'll notice that the manufacturer's instructions that come with the
detector don't say high or low either.The density of a gas is proportional to the weight of a single molecule of
that gas.So you figure relative buoyancy for yourself if you start learning a few
atomic weights:

H=1, He=4, C=12, N=14, O=16.

Add them up for the molecular weights of pure gasses:
H2 = (1+1) = 2, very light
He = (4) = 4, very light
N2 = (14+14 ) = 28, about neutral
O2 = (16+16) = 32, slightly heavy
CO2= (12+16+16)= 44, heavy
CO = (12+16) = 28, about neutral
CH4= (12+4*1) = 18, light (majority part of natural gas)
H2O= (2*1+16) = 18, light (steam)
C2H6=(2*12+6*1)= 30, about neutral (minority part of natural gas)
C3H8=(8 + 3*12)= 42, heavy (propane)
C4H10=(10+4*12)= 58, (butane)
C5H12=(12+5*12)= 70, pentane, lightest part of gasoline

For mixed gasses just take a proportionate average:
Air is 80% N2 + 20% O2 .
air = 0.8(28) + 0.2(32) = 29 (exactly neutral, by definition)

So pure carbon monoxide is actually about 3% lighter than air.
But usually it is made in modest concentrations, mixed in with the normal
combustion products: CO2, H2O. Which are always mixed with the 80% Nitrogen that never participates in
burning. Then that mixes with room air, making an even smaller concentration...

And there are uncertainties...

Some fuels make light exhaust (more H2O), some make heavy (more CO2).
Then when the exhaust cools the light part, H20 (steam), may condense and
drop out. Not to mention that the exhaust gas was expanded when hot, and it
contracts as it cools.

No rule can predict which way it is going to go in most circumstances.

There is however, one constant in all of this and that is CO is a product of incomplete combustion. It can climb up stairs or descend to the basement. The issue is it is heterogeneous in most homes and the detector near the furnace may or may not give you the right reading or any reading at all even if it is working correctly. I have helped develop some industrial units and my feeling is I don't trust them. Ensuring an overabundance of make up air is the best way to safety and I don't even have one in my home.

There that should stir tings up.http://nepacrossroads.com/posting.php?m ... 57&t=7160#

Regards to all

Just some food for thought about CO detector replacement. I don't take any chances with mine. I replace them at the recommended intervals religously. One habit to get into is to mark the date of install on the detector and check the mfg. date at the time of purchace as well. I don't know if there is a set amount of time the stores keep them before purging old stock. I wouldn't be a bit suprised to find a 3 yr. old detector in some stores. I know it's said that if they are in a sealed package that they will keep, but are you willing to take that chance. I get in the habit of checking the date on mine at the same time I clean out my stove for the season. I also change the backup battery in mine at the same time as the smoke detectors. Please heed the advice of the subject line and replace them if it is time. Also replace the batteries in battery operated detectors and replace the backup battery in AC powered units.

Jeff

Generally the type of CO detectors you buy in the store are a Biomimetic type. It basically has a gell like disk in it that "absorbs" CO from the air and changes color. There is another sensor that monitors this change in color and when it senses there is too much CO it will sound the alarm.

CO detectors do not operate the same as a smoke detector. Whereas a smoke detector measures particulates of smoke in the air and checks for obscuration the CO does not.

I happen to work in the fire life safety field and test smoke detectors, heat detectors, duct detectors, flame detectors, wet, dry and preaction sprinkler systems. In fact, my helper almost dumped a Halon system today which I know very little about but managed to explain to him what I did know.

I'm not familiar with the "Biomimetic" term. Would you define what it is?