Image provided by Monika Kubala via Unsplash. 

TL;DR: Methane is not included in the WHO's air quality guidelines, but it's still an air quality problem. Methane is a potent greenhouse gas and a key ozone precursor responsible for 35% of the world's harmful ozone. Methane monitoring spans a wide range of methods, from point-source sensors and fenceline instruments to satellite-based techniques capable of tracking atmospheric methane globally. Turning that data into cleaner air depends on a continuous methane monitoring system that can detect emissions, measure them accurately, and inform both regulations and mitigation strategies.

What is methane monitoring? 

Methane (CH4) is a gas composed of carbon and hydrogen, also known as a hydrocarbon. It is the main component of natural gas. Methane monitoring is the process of detecting and measuring methane concentrations in the air. 

Methane is a potent greenhouse gas. It is more short-lived than carbon dioxide, but far more powerful. In fact, it is more than 28 times as powerful as carbon dioxide at trapping heat in the atmosphere over a 100-year period. The Climate and Clean Air Coalition states that methane has a warming impact 86 times that of carbon dioxide per unit of mass over a 20-year period. 

The total U.S. greenhouse gas emissions in 2022 were 6,343 million metric tons of CO2 equivalent, excluding land sector. This EPA chart breaks down this number by gas type. Percentages may not add up to 100% due to independent rounding. Methane accounted for 11.1% of total U.S. greenhouse gas emissions in 2022. 

Why methane monitoring matters

There are several reasons why methane emission monitoring matters, including: 

  • Methane is a very flammable gas
  • It can displace oxygen and lead to suffocation (in extremely large amounts in confined spaces)
  • Methane negatively impacts the environment by contributing to global warming
  • It can serve as an indicator for gas leakage identification
  • Methane is a key ozone precursor

Methane and air quality: The ground-level ozone connection

Methane harms human health through its connection to global warming. Global warming contributes to extreme weather patterns, contributing to more powerful storms, intense flooding, severe wildfires, and prolonged droughts. These events increase the risk of infectious diseases as well as heat-related illnesses. Methane’s impacts on climate change and health contribute to a global annual loss of about 400 million hours of work due to extreme heat. 

Methane leaks from the oil and gas industry can mix with other harmful chemicals, gases, and volatile organic compounds, harming nearby communities. Yet, one of the most significant ways in which methane harms human health is through its connection to another air pollutant: ground-level ozone (O3). 

Why methane is a ground-level ozone precursor

Ozone is a colorless gas composed of three oxygen atoms. While it is beneficial in the upper atmosphere, it can be harmful in the lower atmosphere, where it contributes to smog. Ozone is formed through chemical reactions in the atmosphere rather than through direct anthropogenic emissions. 

Ozone can have a variety of negative health impacts, including decreased lung function, worsened allergies, difficulty breathing, aggravation of lung disease, and premature death. In 2010, long-term Ozone exposure was responsible for about 1 million premature respiratory deaths around the world. In 2023, ozone accounted for 470,000 COPD deaths globally. Ozone-related deaths are also expected to increase in the coming decades unless regulations are strengthened.  

Ozone does not just harm humans. O3 can also reduce photosynthesis in plants, slowing vegetation growth and making plants more susceptible to damage. 

Methane is a key precursor for ozone. In fact, methane is responsible for 35% of the world's harmful ozone. 

Clarity’s Multi-Gas Module measures ozone along with carbon monoxide, nitrogen dioxide, nitric oxide (NO), and nitrogen oxides (NOx). 

How cow (livestock) methane affects air quality

A single cow belches roughly 220 pounds of methane every year, making cattle the biggest source of agricultural greenhouse gases around the world. The methane that they produce leads to more ozone through chemical reactions in the atmosphere. 

Fortunately, there are ways to make cows more sustainable. Creating more easily digestible cow diets and more efficient livestock production can dramatically reduce methane emissions and protect clean air. 

Why methane is not in WHO air quality guidelines

The WHO Global Air Quality Guidelines set evidence-based recommended levels for certain air pollutants. The aim is to reduce air pollution to a reasonable level to better protect public health. Methane is not among the air pollutants included in the WHO guidelines because its effects on public health are indirect, mediated through global warming and ozone. 

The WHO’s guidelines address air pollutants that affect public health, including particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), and ozone (O3). 

What methane monitoring measures 

Methane monitoring often measures methane concentrations, emissions, and flow rates. A variety of different units and metrics are used for all three types of methane measurement. For instance, methane concentration is often expressed in parts per billion (ppb) or parts per million (ppm), which means the number of methane molecules for every billion or million air molecules. Methane emissions, on the other hand, might be expressed in terms of megagrams or terragrams emitted per year.

How methane monitoring works: Detect, measure, mitigate

There are three steps to implementing methane monitoring: 

  • 1. Detect: Methane monitoring begins by securing funding, choosing a sensor, and setting up an air quality sensor system. Project managers must identify the right locations to place methane monitors to effectively identify methane emissions and leaks. 
  • 2. Measure: Continuous methane monitoring is best for determining high concentrations and emission rates. 
  • 3. Mitigate: Equipped with accurate air quality data, project managers can now properly address emissions, fix methane leaks, raise awareness, and promote positive change. Continuous monitoring also promotes a feedback loop in which methane mitigation measures can be effectively evaluated. 
This graphic demonstrates the three steps to methane gas monitoring.

Methane monitoring methods: ground, satellite, and beyond

There are various ways to monitor methane. Some methods are part of bottom-up assessments, meaning they are small-scale and focus on individual sources at the ground level. In large quantities, they can be used to estimate the larger picture. Other methods are top-down, meaning they are large-scale, often higher-level, and can be used to estimate emissions across broad geographic areas. 

This graphic shows examples of methane measurements across different spatial and temporal scales. 

The different methods for methane monitoring include, but are not limited to:

Method Scale Best for
Point-source measurements (i.e. “calibrated bags,” stack sampling, and more) Very small-scale Monitoring very specific emissions sources, such as stack sampling at combustion exhaust points, monitoring certain valves, and even individual animals.
Perimeter facility line measurements (i.e. open-path spectrometers) Small to medium scale Fenceline monitoring in general is best used for identifying ambient emissions from various types of industrial facilities or emission sites.
Micrometeorological techniques (i.e. towers with fast-response methane sensors) Small to medium scale Towers with ambient methane sensors paired with wind speed + direction sensors can represent the conditions upwind of the sensor.
Aircraft measurements Medium to large scale Aircraft-based measurements can be used to understand emissions from individual facilities, as well as larger regional observations.
Remote sensing technologies (i.e. sensing from satellite platforms) Very large scale Allows for frequent global methane coverage, but is not as precise or accurate as most ground-based instruments.

Where methane comes from and who monitors it

Methane emissions come from many anthropogenic sources, requiring monitoring and mitigation efforts to keep methane air pollution in check. Natural sources, such as wetlands and naturally occurring anaerobic decomposition, can also produce methane. 

This EPA graphic shows United States methane emissions by source between 1990 and 2022. 
Source Why it's monitored Who monitors
Oil & gas Producing, processing, storing, and distributing natural gas produces methane. Similarly, the production, refinement, and storage of crude oil also produce methane. Fugitive leaks can exacerbate the problem. Methane leak monitoring matters to government agencies, nonprofits, and some corporations.
Landfills & waste The decomposition of waste and the treatment of wastewater emit methane. Landfill operators, government agencies, and nonprofits.
Coal mining Methane gas is often trapped in coal formations, having been generated back when the coal was formed. Mining can release methane from coal. This methane can even become explosive when mixed with air. Government agencies, mine operators, and more.
Agriculture Livestock, such as cows, emit methane naturally through their digestive process. Certain manure storage can also produce methane. Government bodies, nonprofits, research groups, and private satellite companies.
Land use, land-use change, and forestry This industry covers certain forest fires and flooded areas. Fires produce methane. Anaerobic decomposition (which occurs in certain flooded areas) also produces methane. Government bodies, nonprofits, and research groups.

Regulations and reporting driving methane monitoring

Certain regulations and programs either require or encourage methane monitoring and/or reductions in methane emissions. Some of these are voluntary while others are binding. These varied programs include: 

Pairing methane monitoring and mitigation with Clarity’s air quality network

There are several different methods of monitoring methane. These include:

  • Thermal conductivity detectors (TCD): These are also known as katharometers. They measure the difference in the thermal conductivity of a carrier gas, which is caused by a change in its chemical makeup. 
  • Catalytic sensors: These sensors are commonly used in mines. They cause a catalytic combustion reaction to understand methane levels. 
  • Optical sensors: Optical sensors use light, such as infrared or lasers, to detect methane. There are various kinds of optical techniques, including non-dispersive infrared technology, direct tunable diode spectroscopy, cavity-enhanced absorption spectroscopy, cavity ring-down spectroscopy, lidar techniques, and more.

Clarity does not currently offer methane monitoring. However, we do offer an array of air quality monitoring solutions, including both fine and coarse particulate matter (PM2.5 and PM10), black carbon, and more. Our Multi-Gas Module monitors ozone (O3) along with carbon monoxide (CO), nitrogen dioxide (NO2), nitric oxide (NO), and nitrogen oxides (NOx). Methane leaves an air quality footprint in the form of ozone, which harms public health and the environment. 

Partner with Clarity to promote clean air and healthier communities.