Carbon monoxide, carbon monoxide, carbon monoxide!!! I have to call out that name three times to draw attention to this very important article. The menace of carbon monoxide poisoning is so huge that any discourse on the subject deserves every keen attention. Carbon monoxide symptoms mimic those of some unserious illnesses and then kills its victims when they least expect. This is very much captured in the Part 1 of this article. Little wonder it is referred to as a silent killer.
[Source: pixabay. CC0 licensed]
If you are an avid reader of major dailies in Nigeria, you will not be new to myriads of ugly reports relating to carbon monoxide poisoning. While the CDC reports about 480 deaths out of about 15,000 people taken to emergency room annually in the US following carbon monoxide poisoning, one would not be wrong to hazard a guess that these US figures would be relatively and substantially insignificant in comparison to any official figure from even the most sparsely populated state in Nigeria if there were to be any official report. Unfortunately, however, there is none!. And this goes on keeping us on a jumbo of IGNORANCE with no existing public awareness in the face of the silent epidemic!
Writing on the Guardian Newspaper of 27 July, 2017, Toying Osasona had observed...
A report puts the number of deaths from generator smoke inhalation in Nigeria between 2008 and 2014 at no fewer than 10,000 and almost every week media reports tell of the deaths from carbon monoxide poisoning.... || Generators: Providing Power and Taking Lives: [Toying Osasona, 27 July 2017, Courtesy of The Guardian].
Reports here, here, here, and here are just the tip of the iceberg relating to cases in which members of families were completely wiped out. The scale is just unimaginable! And the level of ignorance even among the educated, nothing to write home about, no thanks to government I-don't-care posture. Damn! Hence, I wasn't surprised reading 
thanks for bringing this, everyone home in this country need it but DETECTING IS NOT THE MAIN ISSUE. I believe the issue is solving the problem after detecting. [Source: excerpt from Part I]
Little wonder while every building in developed countries has each and every of its rooms fitted with at least one carbon monoxide detector, you hardly see a whole building fitted with even one detector in this part of the world. And people continue to die in droves out of ignorance. Let me emphasize once again: carbon monoxide is odourless, colorless and tasteless. It is undetectable by any of our sense organs. There is no way we can know that its concentration is getting to a dangerous level without a detector. And we use candles, generators, bonfires, lantern, etc which may release the gas in a poorly ventilated environment. So carbon monoxide detectors should be the main thing in our homes!
[Source: pixabay. CC0 licensed]
Haaa! It is as if I have forgotten what should constitute the theme of this Part 2. No regrets, however, over the time given to the prelims so far. Now on to the business of the day:
Different carbon monoxide detectors and How they work
Carbon monoxide detectors are generally and broadly classified into two based on their electrical power requirements. The inexpensive ones needing no battery or electrical power to work are called strip (biomimetic) "blob" detectors while the expensive more sophisticated ones are called electronic detectors, most of which has built-in alarm systems.
Biomimetic blob detectors
Biomimetic detectors are designed to work like hemoglobin which darkens in the presence of carbon monoxide in degree proportional to the concentration of carbon monoxide within the given environment. They are termed biomimetic because they mimic the way our hemoglobin responds to the presence of carbon monoxide. They have a small beige-colored blob (strip) in the middle which turns black in the presence of carbon monoxide.
The phenomenon in which the blob changes colour in the presence of carbon monoxide, is actually a redox (reduction and oxidation) reaction in the presence of a catalyst of palladium and molybdenum salts during which carbon monoxide is oxidized to yield carbon dioxide by the strip chemicals while they themselves (i.e the strip chamicals) are simultaneously reduced, changing the color to black. Once carbon monoxide has been removed via oxidative conversion to CO2, salts of iron, nickel or copper that the strip is also made of are oxidized by the atmospheric oxygen, restoring the blob's color back to beige. So, this boils down to the fact that the strip will regenerate its original color on exposure to air.
Electronic carbon monoxide detectors
Electronic carbon monoxide detectors look similar but actually differ in the ways they respond to the presence of carbon monoxide in the environment. Let's find out the working details of a type of electronic detectors called colorimetric detectors which, like biomimetic detectors described previously, also has chemical blob (strip) that Interacts with a light beam while a photocell measures reflected light to indicate the presence or absence of carbon monoxide. See the gif image below
[Gif Sourced from explainthatstuff.com released under CC BY-NC-SA 3.0 license and authored by Chris Woodford]
In colorimetric detection, if there is no carbon monoxide, the blob strip retains its beige color and maximum rays of light is reflected by the photocell. If, however, carbon monoxide is present, the blob strip turns black, and little or no light is reflected by the photocell because the strip had absorbed most or all of the light rays shining on to it. This absence of reflected light activates the circuitry system, triggering off alarm sound. And hence people nearby are thus alerted of the dangerous level of carbon monoxide in the environment. In the image above, carbon monoxide is shown in blue for tutorial purposes. It is important to remember, however, that carbon monoxide is a colorless, odourless and tasteless gas.
Metal oxide detector
These detectors contain sensors (that are made of metallic oxide of either tin or platinum) in open chambers. In the presence of carbon monoxide, the oxygen of the metallic oxide is taken up and oxidized carbon monoxide to yield carbon dioxide while the metal itself is reduced to pure metal. And energy generated by this redox reaction is given off as heat. The temperature of the chamber is what's monitored by the alarm system circuit based on the fact that heat is generated during the reaction. When heat is produced too quickly, alarm system is triggered to alarm those nearby of dangerous level of carbon monoxide gas in the environment.
Electrolytic detectors
This works in a similar fashion as a battery. Essentially, it is made up of two platinum electrodes that are dipped into a chemical electrolyte. In the presence of carbon monoxide, chemical reaction occurs and the electrolyte conducts electricity which is indicated by the detector circuit, triggering off alarm to draw the attention of people nearby. This type of detectors are said to be the most sensitive, reliable and accurate among all detectors.
In conclusion, the importance of using carbon monoxide detectors cannot be overemphasized. Carbon monoxide is a silent killer, so subtle and confusing that its victims never knew when death process has been triggered until they die very sweetly. It is odourless colorless and tasteless and so cannot be discerned by our natural sense organs. Using carbon monoxide detectors in our homes is, therefore, highly necessary to to avoid this sweet death. It is better to use the less inexpensive biomimetic detectors than using nothing at all if you don't have the wherewithal to acquire the more sophisticated and reliable electronic detectors. Thanks for reading.
References for further reading
- Generators: providing power and taking kife
- Carbon monoxide detector
- What does a carbon monoxide detector do and how does it do it?
- Carbon monoxide detectors
- How carbon monoxide detectors work
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