I have a Nighthawk carbon monoxide detector, 900-0089 (based on KN-COPP-B mechanism).
Supposedly, this has a seven-year lifespan. What wears out?
Daniele
I have a Nighthawk carbon monoxide detector, 900-0089 (based on KN-COPP-B mechanism).
Supposedly, this has a seven-year lifespan. What wears out?
Daniele
The sensor. There are two general types,colourimetric detectors rely upon the change in colour of a chemical similar to that used in the simple paper strip or blob detectors.
Electronic detectors use a platinum or tin sponge (similar to flammable gas detectors) or an electrolytic detector.
In all cases other gasses in the air eventually degrade the sensor so it becomes less responsive (or in the case of colourimetric sensor it triggers).
Some units solve the problem by making the battery a sealed no-replaceable part. The battery life is 6-7 years and when it fails you have to replace the whole unit making sure you get a fresh sensor as well.
There is good article on the common electrochemical sensor at
Our unit starts a timer when you first power it up. Allegedly it will put up a message on its screen (and stop working) after 7 years.
So I presume it's not actually possible to test whether it's working satisfactorily well or not, without getting a cowboy builder to mess up your boiler for you.
Daniele
With your car engine cold (so the catalytic converter is not working) put a binsack over your car's exhaust, fill it and place the CO detector inside. If it doesn't go off in a minute it is certainly dead.
You can also buy test sprays such as
And that's not going to help much if the thing's going to stop working effectively sometime in the near future anyway. One would prefer to know that it's going to be working until the next test.
Daniele
If it's a colourimetric detector, won't that poison the sensor? In other words, if you test one of those coloured spots with CO and make it go black, won't it stay black after the event? They wouldn't be much use otherwise - it's not like you check them every 5 minutes.
Theo
If it's a sophisticated one, the lifetime expiry chip. They self-disable ba= sed on date.
In general, it's the sensor itself. These do have a limited lifetime. They'= re worn out by simple exposure to air, but particularly by a few compounds = to which they're sensitive. Ammonia is one, so if you have sprogs and nappi= es, don't keep the CO monitor next to them.
Ours claims it will give a beep every 30 seconds when the time is up. But that's also the code for 'flat battery'. Changed the battery this afternoon (installed 2008, unit expires 2016) and it beeped for quite a while - even when I took it out in the garden. Eventually it settled down into flashing-the-green-LED-every-30s which is the normal working state, so I /assume/ it's working...
There's some nice red flags that pop out when you take the batteries out, preventing the lid going on, which at least mean you can't install it without any batteries inside.
Theo
unlikely to work as modern cars burn the CO in the catlayst
Not until they warm up though
Read what he said.
Is that the equivalent of dropping it into a bucket of water? It doesn't tell you if it was working but you need a new one after the test.
No, it should be fine afterwards unless it is one of the quite rare colourimetric detector. The detector is poisoned not by CO but other pollutants in the air, especially silicone polish sprays for the platinum sponge sort.
Not by the unburnt fuel?
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