Carbon Monoxide Detectors

Last week we covered how a draft inducer and it’s attached pressure sensor can help prevent Carbon Monoxide from leaking out of a furnace. This week we’re moving up to the next line of defense: a dedicated Carbon Monoxide Detector. These are often installed in new homes and offices as required by local building codes in most of the United States. Where they’re not installed by construction, they’re usually installed by the facility’s owner as a precaution.


What’s the Big Deal?

Carbon Monoxide is one of the deadliest, common compounds in the world. It’s is a colorless, odorless gas that will kill you at the right concentrations. There’s only two ways for someone to know they’ve been exposed to a harmful dose: Use a detector or Recognise the Symptoms before it’s too late.

The initial symptoms include headache, dizziness, weakness, vomitting, chest pain, and confusion. In large part, these common symptoms can be attributed to hundreds of other ailments, including the common flu. Greater exposure can lead to passing out, arrhythmia, seizures, and death. Even then, there will be longterm complications, including memory problems, movement disabilities, and fatigue.

Most people are not able to detect and react to these symptoms as Carbon Monoxide poisoning before it’s too late. They’re often waived off as a flue or some other lesser problem until it’s too late.


How Do We Detect An Invisible, Colorless, Odorless Gas?

While Carbon Monoxide itself is invisible and nearly undetectable in isolation, it does react to other materials. Common detectors use Opto-Chemical, Biomimetic, Electrochemical, and Silicon-Chip based detection systems. These all rely on the gas to change something we can detect more easily.

Opto-Chemical detectors are chemical pads which change color in the presence of Carbon Monoxide. They’re cheap and easy to deploy, but they do not give audible warnings. They’re essentially stickers to be placed on the wall. When they change color, someone has to notice it and begin an evacuation.

Biomimetic Detectors work like the hemoglobin in our blood. A chemical mixture will darken as more Carbon Monoxide builds up. This darkening can be measured with an IR LED and a photodiode. When the light passing through is sufficiently blocked, the alarm sounds. This particular design is believed to be resistant to false alarms and is therefore far more common in hospitals, hotels, and other large facilities.

Electrochemical Detectors use a fuel cell which reacts to the amount of Carbon Monoxide present. The higher the concentration, the higher the fuel cell’s output current. This allows for accurate detection and sensing. The biggest draw back here is the added complexity. This approach costs more to implement and may have a shorter lifespan than other detector designs.

Semiconductor Detectors use a tin dioxide sensing element. It is heated to 400 Degrees Celsius, at which point increases in Carbon Monoxide reduce the wire’s resistance, while increases in oxygen presence will decrease it. This design needs a hard-wired power source in most installations and has fallen into lesser use as more power efficient, long-lived sensing technologies have developed.


Is This Really Necessary?


Furnace-based safety systems can only go so far. This poses significant problems for ensuring an entire facility is safe. Our methods of detecting hazards on the furnace do not guarantee the system will shutdown before a gas leak occurs. Further, ovens, cooktops, and other appliances don’t always have detection devices in them. Some of the same faults that occur with furnaces can be just as deadly in the kitchen. Carbon Monoxide Detectors are cheap, readily available, and essential.


What About Carbon Dioxide?

CO2 is the more well known threat. It’s about as hard to detect as regular CO and about as deadly. The problem is that extra oxygen atom really complicates detection. CO2 detection hardware has a starting price around $100, with good equipment falling closer to the $1000 mark.

In most circumstances, a dedicated CO2 detector probably isn’t necessary. If there’s Carbon Dioxide, there is probably Carbon Monoxide as well. The notable exception is industrial facilities. These probably have bigger challenges to overcome, more sources of specific gases that require specialized detectors. That’s a whole can of yarn for another day and a specialized set of solutions.



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