Sensors in Carbon Monoxide Detectors
Electrochemical sensors use a gel to detect CO. Electrochemical sensors are mainly used to detect Oxygen and toxic gas. They measure a chemical reaction within the sensor that creates an electrical output proportional to the CO level. Essentially, EC sensors are small fuel cells composed of noble metal electrodes in an electrolyte.
AlphaSense is one of the most popular manufacturers of electrochemical oxygen sensors. Their sensors are used in dozens of 4-gas detectors and portable safety meters used worldwide.
Why Do We Need to Detect CO?
Carbon Monoxide is an odorless, tasteless and generally undetectable to humans. This makes it a dangerous gas, as too much exposure can cause carbon monoxide poisoning. Carbon monoxide poisoning occurs when too much CO builds up in your bloodstream and your body replaces the oxygen in red blood cells. Symptoms can include headaches, vomiting, dizziness, weakness, confusion, nausea, unconsciousness and even death.
The best way to prevent carbon monoxide poisoning is to install a CO gas detector in your home, workplace, auto shop, or other area where CO is likely to occur. Learn about carbon monoxide detectors in the home. CO is largely produced by incomplete combustion, for example when you burn any fuel such as gasoline or propane.
Carbon Monoxide Safety in Parts Per Million
There are several ways that electrochemical CO sensors can be used to protect you. The main method that most people immediately think of are the standard carbon monoxide detectors that you find in homes, schools, and offices.
There are also personal CO sensing devices that are much more effective for those who work around CO more than the average person. For example, the GasLab Plus Carbon Monoxide Detector is designed to measure carbon monoxide concentrations in a variety of applications like HVAC or air quality testing.
For extra safety, GasLab offers wearable, rechargeable CO Safety Monitors for personal safety in the field. These are designed for people who work in confined spaces such as garages, ice rinks, engine compartments, or anywhere CO buildup can occur. If CO levels get too high, audible and visual alarms warn the user.
Carbon Monoxide Exposure Limits
There are certain levels of CO concentrations that are deemed average and safe for human occupation:
- 1 parts per million (ppm) is the current average CO level on the planet
- OSHA limits long-term workplace exposure levels to 50 ppm (parts per million)
- Symptoms of mild carbon monoxide poisoning include headaches and dizziness at concentrations less than 100 ppm
- Concentrations as low as 700 ppm can be life-threatening
It is important to keep in mind the affects vary depending on several factors. The 
concentration of CO, time of exposure, age, gender, and overall health affect the danger level. Take for example this instance from the University of Iowa where they found a concentration of 400ppm CO can cause headaches in 1 to 2 hours. In 3 to 5 hours the same concentration can lead to unconsciousness and death. Accompanying increase in respiration rate can shorten the time to critical levels.
References:
https://delphian.com/electrochemical%20sensors.htm
https://home.howstuffworks.com/home-improvement/household-safety/carbon-monoxide-detector1.htm
https://www.abe.iastate.edu/extension-and-outreach/carbon-monoxide-poisoning-health-effects-aen-166/
https://www.nsc.org/home-safety/safety-topics/other-poisons/carbon-monoxide