Carbon monoxide, one of the most abundant pollutant gases, is indetectable to humans as it can not be seen, smelled, or tasted. Exposure to high levels of CO can cause CO poisoning leading to serious health issues, giving it the name “The Silent Killer”. CO monitoring is the most effective way to know if you are at risk of carbon monoxide exposure. This article covers information on carbon monoxide, its sources, permissible levels in the ambient air, health and environmental impact, possible corrective measures, need for carbon monoxide monitors as well as different methods of CO monitoring.
What is CO?
Carbon monoxide is a colorless, odorless, non-irritating, and tasteless poisonous gas found in the atmosphere. Incomplete combustion of carbon-containing fuels such as coal, gasoline, natural gas, oil, and wood produce this critical air pollutant.
Carbon monoxide gas consists of one carbon atom and one oxygen atom. The molecular weight of carbon monoxide is similar to that of air about 28.01 g/mole. It is flammable and reacts vigorously with oxygen, acetylene, chlorine, fluorine, and nitrous oxide. Also, it is slightly soluble in water, blood serum, and plasma.
Carbon monoxide in Atmosphere
CO is naturally present in the atmosphere at very low concentrations of about 0.2 ppm which is not harmful to humans. CO is released naturally from the eruption of volcanoes, forest fires, etc. However, human activities are the biggest source of CO emissions. It remains in the atmosphere for about 2 months and then it eventually reacts with oxygen to form carbon dioxide.
CO is produced due to incomplete combustion of fuels (combustion is when fuel reacts with oxygen to produce heat). If enough oxygen is not available for combustion, it results in the partial oxidation of carbon-containing compounds. During such combustion, carbon monoxide (CO) is produced instead of carbon dioxide (CO2).
The levels of carbon monoxide are typically highest during winters as cold temperatures inhibit the combustion processes resulting in higher CO formation. Additionally, the meteorological conditions during winters trap the pollutants close to the ground.
Natural sources such as volcanoes, bush/forest fires, metabolism of animals, and even lightning lead to carbon monoxide emissions.
Carbon monoxide is majorly released from vehicular exhaust due to incomplete combustion of fuel in cars, trucks, airplanes, and boats. Additional sources include breathing in tobacco smoke, burning of biomass for cooking, equipment, or appliances such as heaters, barbeques, gas stoves, gas water heaters, fireplaces, etc.
The major industrial source of carbon monoxide is from the combustion of fuels such as coal, natural gas, and coke in industrial plants. Also, CO is emitted from various industrial processes such as metal manufacturing, mining of metal ore and coal, food processing industries, power generation, oil and gas extraction and refining processes oil and gas from either land or sea, production of chemicals, manufacturing of concrete and plaster, etc.
Permissible levels of Carbon Monoxide
The breakpoints concentrations describing the quality of air based on the carbon monoxide concentrations for different countries are given below. In India, the daily average CO levels of up to 2 mg/m3 are considered satisfactory.
Table: Breakpoints of carbon monoxide (mg/m3)
|India (8-hr)||US (24-hr)||China (24-hr)||EU (8-hr)|
|AQI Category||Breakpoint concentration||AQI Category||Breakpoint concentration||AQI Category||Breakpoint concentration||AQI Category|
|Moderately polluted||10||Unhealthy for sensitive||14||Lightly Polluted||14||Medium|
|Very Poor||34||Very Unhealthy||35||Heavily Polluted||36||Very high|
Health & Environmental Impact of carbon monoxide
CO is known for its alarming effect on human health. CO has a higher affinity (200 times) than oxygen to hemoglobin (Hb), which is the protein in the blood that carries oxygen from the lungs to cells throughout the body. It replaces the oxygen in the bloodstream and binds itself to hemoglobin to form carboxyhemoglobin (COHb) and thereby impairs the oxygen-carrying capacity of the body. Moreover, inhaling CO in higher amounts causes oxygen starvation which affects vital organs like the heart, brain, and nervous system.
It is more dangerous because humans cannot detect higher levels of CO as it has no taste or smell and cannot be seen. The people suffering from some type of heart disease are even more vulnerable as they already have a reduced ability for getting oxygenated blood to their hearts in situations where the heart needs more oxygen than usual. In these situations, short-term exposure to elevated CO may result in more critical health issues.
Initial symptoms of CO poisoning may include flu-like symptoms such as headache, dizziness, weakness, nausea, and fatigue. In case of prolonged or high exposures, this may advance to vomiting, loss of consciousness, and collapse. Further, it may lead to coma or death if high exposures continue. People with coronary heart disease may suffer from chest pain.
Carbon monoxide is a very weak direct greenhouse gas that reacts with the hydroxyl radicals in the atmosphere and reduces their abundance. The presence of hydroxyl radicals is important in the atmosphere as it reacts with strong greenhouse gases and helps reduce their effect on global warming. Thus, the carbon monoxide emitted into the atmosphere indirectly contributes to global warming. CO also contributes to the formation of ozone in the air which is another critical air pollutant.
The reactions of CO in the atmosphere leading to hydroxyl conversion and ozone formation are:
CO + OH ➝ CO2 + H
H + O2 ➝ HO2
HO2 + NO ➝ OH + NO2
NO2 + sunlight ➝ NO + O
O + O2 ➝ O3
Net: CO + 2O2 ➝ CO2 + O3
Possible corrective measures
The primary action is CO monitoring i.e. to measure how much of CO concentrations you are exposed to. In addition to this following corrective measures can be taken:
- If you detect the presence of high CO levels, get some fresh air, or provide proper ventilation.
- Have a walk, use bicycles or public transport whenever possible.
- Additionally, promote the use of alternative fuels.
- Avoid keeping your vehicle idle for long.
- Avoid areas with traffic congestions. Breathing such polluted air daily also leads to health effects in the long run.
- Avoid using fuel-burning appliances such as generators or engines in low ventilated areas.
- Also, proper usage and preventive maintenance of heating components such as gas or water heaters or any other gas, oil, or coal-burning appliances, etc.
Measurement methods of CO monitoring
Different working principles for carbon monoxide monitoring in the ambient environment are nondispersive infrared absorption (NDIR), semiconductor, and electrochemistry.
Nondispersive infrared absorption (NDIR) – Carbon monoxide absorbs infrared radiation at a particular frequency. When the gas sample is exposed to infrared radiation, the infrared radiation absorbed by the CO molecules present in the gas sample is measured by the detector in a non-dispersive photometer. However, the use of this principle in carbon monoxide monitors may result in the possibility of potential interferences from other gases that absorb infrared radiation similar to CO.
Semiconductor – When a metal oxide semiconductor-based carbon monoxide monitor is exposed to an air sample, the CO molecules react on the metal oxide surface of the sensor and dissociate into charged ions which alter the resistance of the film. This interaction is measured as a signal and is converted to the gas concentration. However, the energy consumption of such carbon monoxide monitors is higher compared to other CO monitors.
Electrochemical – CO monitors working on the electrochemical principle are operated based on the diffusion of carbon monoxide gas into the sensor which results in the production of an electrical signal proportional to the CO concentration. Therefore, it allows accurate measurement of even low concentrations of carbon monoxide, which is essential in carbon monoxide monitoring in the ambient conditions.
Among all the above principles of CO monitoring, carbon monoxide monitors based on electrochemistry are typically found to be preferred for ambient air monitoring as they yield more accurate CO concentrations and are inexpensive in comparison with the others.
Oizom’s working principle for CO monitoring
Oizom’s POLLUDRONE measures more than 30 parameters including gaseous pollutants like carbon monoxide (CO), sulfur dioxide (SO2), nitric oxide (NO) nitrogen dioxide (NO2); dust particulates like PM2.5, PM10, noise and weather parameters like rainfall, wind speed and wind direction. Most of the sensors measuring gases including carbon monoxide work on the principle of electrochemical sensing. The active sampling powered sensor-based air quality monitor POLLUDRONE is deployed across several cities, campuses, universities and is used for drawing actionable insights to tackle the rise in ambient carbon monoxide concentrations.
5 reasons why CO monitoring is important
- Carbon monoxide can be released by almost any combustion source such as vehicles, gas-burning appliances such as gas heaters, generators, furnaces in enclosed places and many such common sources present everywhere, adding to the carbon monoxide levels already present in the atmosphere.
- CO cannot be smelled or tasted and cannot be seen and thus remains undetectable by humans even at higher levels making it a “silent killer”.
- Carbon Monoxide poisoning is lethal as it hinders the ability of the blood to carry oxygen to vital organs such as the heart and brain.
- CO monitoring is an efficient way to prevent CO poisoning as it helps detect the buildup of carbon monoxide levels and alerts when a certain level is exceeded.
- Real-time carbon monoxide monitoring helps in calculating air quality index to deliver health advisories as well as formulating an action plan to meet standards.