How Carbon Monoxide Detectors Work

The purpose of a carbon monoxide detector is to constantly monitor the levels of this dangerous gas in the air, and then sound an alarm if the levels get too high. For those of you who aren’t familiar with CO gas, it’s something which you can’t see; smell, or taste, and you often don’t know you’ve been exposed until it’s too late.

Early Sensors

Historically there were a number of methods detectors used with the earliest kind being a chemical sensor which basically made a strip of white paper turn brown in the presence of CO. The obvious problem with that approach was that you had to be looking at the ‘sensor’ in order to know there was a problem – this is of course completely useless when you’re asleep or simply not paying attention to it. Also the properties of these types of sensors were that they were cumulative, meaning that they only ever turned darker – they didn’t lighten up when CO levels fell.
As a result sensors were developed which could measure both increasing and decreasing levels, and were connected to audible alarms.

Biomimetic

These rely on a chemical process, which is not at all unlike the way haemoglobin works in your blood, causing a chemical compound to turn progressively darker as the carbon monoxide levels increase (similar to the way blood turns darker when exposed to the oxygen in the air). Light is then beamed at the compound, usually in the infrared spectrum, and a sensor measures the amount of light reflected. The less that light is reflected is an indication that the compound has turned dark and therefore must be in the presence of carbon monoxide. The level of darkening is directly proportional to the amount of light absorbed, therefore the light sensor is effectively measuring not only that CO is present, but also the concentration of the gas in the air as well. This method is regarded by scientists as being the most reliable due to its extremely low ‘false alarm’ rate, however it is also more costly than other methods so it’s generally only deployed in critical settings such as Hospitals and Hotels where false alarms can be highly disruptive, and expensive.

Electrochemical

This type of sensor is the main one you will find in carbon monoxide detectors designed for home use. They employ a very clever use of fuel cell technology where the amount of power they produce is proportional to the amount of carbon monoxide they are exposed to.
The upside to these types of sensors is that they are both easy to manufacture, and they require less power to operate than Biomimetic sensors – the downside is that they are sensitive to fluctuations of carbon monoxide levels in the air and have a slightly higher tendency to produce ‘false positives’ caused by temporary increases from things like cigarette smoking. However the occasional ‘false alarm’ in the home environment doesn’t come with the same cost of evacuating a hospital ward, so these are generally the best option for home use – which is why most leading carbon monoxide detector alarm manufactures use these sensors.

Summary

Now that you understand how CO alarms work, and which types are suitable for domestic use, I strongly recommend you read up on Carbon Monoxide Detector Installation before installing them in your home.

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