A USGS scientist aims the viewfinder of an infrared spectrometer to measure the chemistry of volcanic gas on the last day of the Nāpau eruption, September 20, 2024. USGS photo by P. Nadeau.
Who monitors volcanic gases emitted by Kīlauea and how is it done?
The U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) determines the amount and composition of gases emitted by Kīlauea Volcano. Changes in gas emissions can reveal important clues about the inner workings of a volcano, so they are measured on a regular basis.
HVO scientists use both remote and direct sampling techniques to measure compositions and emission rates of gas from Kīlauea Volcano.
To determine the rate at which sulfur dioxide (SO2) is emitted, HVO scientists measure the amount of ultraviolet (UV) radiation energy absorbed by the volcanic gas plume as sunlight passes through it. They do this by attaching a mini-UV spectrometer (Flyspec) to a field vehicle and driving beneath the plume.
The amount of carbon dioxide (CO2) emitted by Kīlauea is measured using a small infrared analyzer (LI-COR). Scientists drive this instrument through a gas plume, along with the Flyspec, while it continuously and directly samples the ground-level cross-section of the plume.
Another tool used to measure the relative abundance of some gases, including SO2, CO2, hydrogen chloride (HCl), hydrogen fluoride (HF), carbon monoxide (CO) and water vapor (H20), is the Fourier Transform infrared spectrometer (FTIR), which can continuously sample gas in a volcanic plume. The FTIR measures the amount of light absorbed by gases along an open path between the spectrometer and an infrared source, such as an eruptive vent.
Learn more:
Related
Does vog (volcanic smog) impact plants and animals?
Should I cancel my plans to visit Hawai`i Island because of sulfur dioxide (SO2) and vog?
What health hazards are posed by vog (volcanic smog)?
What is "vog"? How is it related to sulfur dioxide (SO2) emissions?
Where and how do sulfur dioxide and volcanic gases (vog) affect air quality in Hawaii?
What gases are emitted by Kīlauea and other active volcanoes?
How much sulfur dioxide (SO2) gas does Kīlauea emit?
Does ash ever erupt from Kīlauea Volcano?
Why is it important to monitor volcanoes?
Is it dangerous to work on volcanoes? What precautions do scientists take?
What kind of school training do you need to become a volcanologist?

A USGS scientist aims the viewfinder of an infrared spectrometer to measure the chemistry of volcanic gas on the last day of the Nāpau eruption, September 20, 2024. USGS photo by P. Nadeau.
An HVO gas scientist carrying portable gas sensor (yellow box) near Mauna Loa summit in June 2023. The white material on the ground in this photo is snow. USGS photo by P. Nadeau.
An HVO gas scientist carrying portable gas sensor (yellow box) near Mauna Loa summit in June 2023. The white material on the ground in this photo is snow. USGS photo by P. Nadeau.

An HVO scientist samples the gas around a crack identified as emitting elevated levels of carbon dioxide (a volcanic gas) on the down-dropped block within Kīlauea caldera. The sample will later be analyzed to determine its complete chemical composition. This work was conducted within a closed area of Hawai‘i Volcanoes National Park, with park permission.
An HVO scientist samples the gas around a crack identified as emitting elevated levels of carbon dioxide (a volcanic gas) on the down-dropped block within Kīlauea caldera. The sample will later be analyzed to determine its complete chemical composition. This work was conducted within a closed area of Hawai‘i Volcanoes National Park, with park permission.

The 2018 Kīlauea Volcano eruption marked the first time the federal government used Unmanned Aircraft Systems (UAS) to assist in an eruption response in the United States.
The 2018 Kīlauea Volcano eruption marked the first time the federal government used Unmanned Aircraft Systems (UAS) to assist in an eruption response in the United States.

Hawaiian Volcano Observatory field crews establish a new MultiGAS volcanic gas monitoring station on the south side of Kīlauea Volcano's caldera. Currently, sulfur dioxide emission rates from the summit remain low. The station will collect data to track emission rates and concentrations over time. Photo by Frank Younger.
Hawaiian Volcano Observatory field crews establish a new MultiGAS volcanic gas monitoring station on the south side of Kīlauea Volcano's caldera. Currently, sulfur dioxide emission rates from the summit remain low. The station will collect data to track emission rates and concentrations over time. Photo by Frank Younger.

Title: What on Earth is going on at Kilauea Volcano?
- First significant summit explosions in nearly a century
- Largest summit collapse volume since at least 1800
- Voluminous fissure eruptions feeding channelized lava flow
- Unparalleled new opportunities for understanding the volcanic system
Title: What on Earth is going on at Kilauea Volcano?
- First significant summit explosions in nearly a century
- Largest summit collapse volume since at least 1800
- Voluminous fissure eruptions feeding channelized lava flow
- Unparalleled new opportunities for understanding the volcanic system

HVO's geochemist uses a Fourier Transform Infrared Spectrometer (FTIR) instrument to track volcanic gases emitted from the lava lake with Halema‘uma‘u Crater. These measurements help detect changes in gas composition, which can provide insight into the inner workings of Kīlauea Volcano.
HVO's geochemist uses a Fourier Transform Infrared Spectrometer (FTIR) instrument to track volcanic gases emitted from the lava lake with Halema‘uma‘u Crater. These measurements help detect changes in gas composition, which can provide insight into the inner workings of Kīlauea Volcano.

Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.

Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
This photo was taken from the lamp on the other side of the plume. The FTIR is the small dark silhouette on the rim across the crater gap.
This photo was taken from the lamp on the other side of the plume. The FTIR is the small dark silhouette on the rim across the crater gap.
HVO gas geochemists deployed a FTIR spectrometer on the east rim of Pu`u `Ō `ō crater. The FTIR measures the composition of the East Wall vent gases by "looking" through the plume at an infrared lamp (obscured by fume in this photo)
HVO gas geochemists deployed a FTIR spectrometer on the east rim of Pu`u `Ō `ō crater. The FTIR measures the composition of the East Wall vent gases by "looking" through the plume at an infrared lamp (obscured by fume in this photo)

The erupting vent within Halema'uma'u Crater at Kilauea's summit (see http://hvo.wr.usgs.gov/kilauea/timeline/ for links describing eruptive activity at the summit of Kilauea Volcano) typically produces a white to gray gas plume dominated by steam.
The erupting vent within Halema'uma'u Crater at Kilauea's summit (see http://hvo.wr.usgs.gov/kilauea/timeline/ for links describing eruptive activity at the summit of Kilauea Volcano) typically produces a white to gray gas plume dominated by steam.
Recommended capabilities and instrumentation for volcano monitoring in the United States
Views of a century of activity at Kīlauea Caldera—A visual essay
Groundwater dynamics at Kīlauea Volcano and vicinity, Hawaiʻi
Kīlauea’s 2008–2018 summit lava lake—Chronology and eruption insights
U.S. Geological Survey 2018 Kīlauea Volcano eruption response in Hawai'i—After-action review
Preliminary analyses of volcanic hazards at Kīlauea Volcano, Hawai‘i, 2017–2018
Volcanic air pollution hazards in Hawaii
One hundred volatile years of volcanic gas studies at the Hawaiian Volcano Observatory
The ongoing Puʻu ʻŌʻō eruption of Kīlauea Volcano, Hawaiʻi: 30 years of eruptive activity
Mauna Loa--history, hazards and risk of living with the world's largest volcano
Sulfur dioxide emission rates from Kilauea Volcano, Hawaii, 2007-2010
Kilauea— An explosive volcano in Hawai‘i
Related
Does vog (volcanic smog) impact plants and animals?
Should I cancel my plans to visit Hawai`i Island because of sulfur dioxide (SO2) and vog?
What health hazards are posed by vog (volcanic smog)?
What is "vog"? How is it related to sulfur dioxide (SO2) emissions?
Where and how do sulfur dioxide and volcanic gases (vog) affect air quality in Hawaii?
What gases are emitted by Kīlauea and other active volcanoes?
How much sulfur dioxide (SO2) gas does Kīlauea emit?
Does ash ever erupt from Kīlauea Volcano?
Why is it important to monitor volcanoes?
Is it dangerous to work on volcanoes? What precautions do scientists take?
What kind of school training do you need to become a volcanologist?

A USGS scientist aims the viewfinder of an infrared spectrometer to measure the chemistry of volcanic gas on the last day of the Nāpau eruption, September 20, 2024. USGS photo by P. Nadeau.
A USGS scientist aims the viewfinder of an infrared spectrometer to measure the chemistry of volcanic gas on the last day of the Nāpau eruption, September 20, 2024. USGS photo by P. Nadeau.
An HVO gas scientist carrying portable gas sensor (yellow box) near Mauna Loa summit in June 2023. The white material on the ground in this photo is snow. USGS photo by P. Nadeau.
An HVO gas scientist carrying portable gas sensor (yellow box) near Mauna Loa summit in June 2023. The white material on the ground in this photo is snow. USGS photo by P. Nadeau.

An HVO scientist samples the gas around a crack identified as emitting elevated levels of carbon dioxide (a volcanic gas) on the down-dropped block within Kīlauea caldera. The sample will later be analyzed to determine its complete chemical composition. This work was conducted within a closed area of Hawai‘i Volcanoes National Park, with park permission.
An HVO scientist samples the gas around a crack identified as emitting elevated levels of carbon dioxide (a volcanic gas) on the down-dropped block within Kīlauea caldera. The sample will later be analyzed to determine its complete chemical composition. This work was conducted within a closed area of Hawai‘i Volcanoes National Park, with park permission.

The 2018 Kīlauea Volcano eruption marked the first time the federal government used Unmanned Aircraft Systems (UAS) to assist in an eruption response in the United States.
The 2018 Kīlauea Volcano eruption marked the first time the federal government used Unmanned Aircraft Systems (UAS) to assist in an eruption response in the United States.

Hawaiian Volcano Observatory field crews establish a new MultiGAS volcanic gas monitoring station on the south side of Kīlauea Volcano's caldera. Currently, sulfur dioxide emission rates from the summit remain low. The station will collect data to track emission rates and concentrations over time. Photo by Frank Younger.
Hawaiian Volcano Observatory field crews establish a new MultiGAS volcanic gas monitoring station on the south side of Kīlauea Volcano's caldera. Currently, sulfur dioxide emission rates from the summit remain low. The station will collect data to track emission rates and concentrations over time. Photo by Frank Younger.

Title: What on Earth is going on at Kilauea Volcano?
- First significant summit explosions in nearly a century
- Largest summit collapse volume since at least 1800
- Voluminous fissure eruptions feeding channelized lava flow
- Unparalleled new opportunities for understanding the volcanic system
Title: What on Earth is going on at Kilauea Volcano?
- First significant summit explosions in nearly a century
- Largest summit collapse volume since at least 1800
- Voluminous fissure eruptions feeding channelized lava flow
- Unparalleled new opportunities for understanding the volcanic system

HVO's geochemist uses a Fourier Transform Infrared Spectrometer (FTIR) instrument to track volcanic gases emitted from the lava lake with Halema‘uma‘u Crater. These measurements help detect changes in gas composition, which can provide insight into the inner workings of Kīlauea Volcano.
HVO's geochemist uses a Fourier Transform Infrared Spectrometer (FTIR) instrument to track volcanic gases emitted from the lava lake with Halema‘uma‘u Crater. These measurements help detect changes in gas composition, which can provide insight into the inner workings of Kīlauea Volcano.

Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.

Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
This photo was taken from the lamp on the other side of the plume. The FTIR is the small dark silhouette on the rim across the crater gap.
This photo was taken from the lamp on the other side of the plume. The FTIR is the small dark silhouette on the rim across the crater gap.
HVO gas geochemists deployed a FTIR spectrometer on the east rim of Pu`u `Ō `ō crater. The FTIR measures the composition of the East Wall vent gases by "looking" through the plume at an infrared lamp (obscured by fume in this photo)
HVO gas geochemists deployed a FTIR spectrometer on the east rim of Pu`u `Ō `ō crater. The FTIR measures the composition of the East Wall vent gases by "looking" through the plume at an infrared lamp (obscured by fume in this photo)

The erupting vent within Halema'uma'u Crater at Kilauea's summit (see http://hvo.wr.usgs.gov/kilauea/timeline/ for links describing eruptive activity at the summit of Kilauea Volcano) typically produces a white to gray gas plume dominated by steam.
The erupting vent within Halema'uma'u Crater at Kilauea's summit (see http://hvo.wr.usgs.gov/kilauea/timeline/ for links describing eruptive activity at the summit of Kilauea Volcano) typically produces a white to gray gas plume dominated by steam.