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.
How are volcanic gases measured?
Instruments to measure sulfur dioxide and carbon dioxide can be mounted in aircraft to determine the quantity of gas being emitted on a daily basis. Such instruments can also be used in a ground-based mode. An instrument that detects carbon dioxide can be installed on a volcano and configured to send data continuously via radio to an observatory. Sulfur dioxide in volcanic clouds can also be measured from space with instruments aboard satellites.
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Related
Why is it important to monitor volcanoes?
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Lava sampling: Why do we do it?
Who monitors volcanic gases emitted by Kīlauea and how is it done?
What gases are emitted by Kīlauea and other active volcanoes?

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 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.

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.

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.
USGS geologist Laura Clor (right) and Rachel Teasdale (California State University – Chico, left) collect gas samples from a thermal feature at Sulphur Works in Lassen Volcanic National Park.
USGS geologist Laura Clor (right) and Rachel Teasdale (California State University – Chico, left) collect gas samples from a thermal feature at Sulphur Works in Lassen Volcanic National Park.
USGS geologist Deborah Bergfeld collects a gas sample from a superheated (hotter than the boiling point) fumarole in Little Hot Springs Valley at Lassen Volcanic National Park.
USGS geologist Deborah Bergfeld collects a gas sample from a superheated (hotter than the boiling point) fumarole in Little Hot Springs Valley at Lassen Volcanic National Park.

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.

Scientists collect volcanic gas data using a Fourier Transform Infrared spectrometer (FTIR). During the Kamoamoa eruption, sulfur dioxide emission rates from Kīlauea’s East Rift Zone reached the highest levels since the episodes of high-fountaining at Pu‘u‘ō‘ō (1983–1986) with an average rate of 8,500 tonnes per day and a peak value of 11,000 tonnes per day.
Scientists collect volcanic gas data using a Fourier Transform Infrared spectrometer (FTIR). During the Kamoamoa eruption, sulfur dioxide emission rates from Kīlauea’s East Rift Zone reached the highest levels since the episodes of high-fountaining at Pu‘u‘ō‘ō (1983–1986) with an average rate of 8,500 tonnes per day and a peak value of 11,000 tonnes per day.

Since the opening of the Overlook vent in Halema‘uma‘u Crater in 2008, FTIR spectroscopy has been used to monitor summit eruptive-gas composition. Infrared energy emitted by the lava lake surface (top left) is absorbed by gases present in the path between the instrument and the lak surface.
Since the opening of the Overlook vent in Halema‘uma‘u Crater in 2008, FTIR spectroscopy has been used to monitor summit eruptive-gas composition. Infrared energy emitted by the lava lake surface (top left) is absorbed by gases present in the path between the instrument and the lak surface.

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.

A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06. This photo was taken during a FLIR/maintenance flight on January 24, 2006.
A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06. This photo was taken during a FLIR/maintenance flight on January 24, 2006.
USGS geologists gathered samples by hand from vents on the dome and crater floor. Additionally, sulfur dioxide gas was measured from a specially equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano.
USGS geologists gathered samples by hand from vents on the dome and crater floor. Additionally, sulfur dioxide gas was measured from a specially equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano.
ARRA-funded student Taryn Lopez (Univ. Alaska-Fairbanks) sampling gas emissions at fumarole next to dome at the summit of Augustine volcano.
ARRA-funded student Taryn Lopez (Univ. Alaska-Fairbanks) sampling gas emissions at fumarole next to dome at the summit of Augustine volcano.
Kilauea's active summit vent is on the southeast side of Halema'uma'u Crater. In this photo, the floor of Halema'uma'u stretches out beyond the vent, and the summit of Kilauea Volcano is at upper right. The observation tower at the Hawaiian Volcano Observatory is the highest bump in the photo at Kilauea's summit.
Kilauea's active summit vent is on the southeast side of Halema'uma'u Crater. In this photo, the floor of Halema'uma'u stretches out beyond the vent, and the summit of Kilauea Volcano is at upper right. The observation tower at the Hawaiian Volcano Observatory is the highest bump in the photo at Kilauea's summit.
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Related
Why is it important to monitor volcanoes?
Is it dangerous to work on volcanoes? What precautions do scientists take?
How can we tell when a volcano will erupt?
Lava sampling: Why do we do it?
Who monitors volcanic gases emitted by Kīlauea and how is it done?
What gases are emitted by Kīlauea and other active volcanoes?

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 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.

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.

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.
USGS geologist Laura Clor (right) and Rachel Teasdale (California State University – Chico, left) collect gas samples from a thermal feature at Sulphur Works in Lassen Volcanic National Park.
USGS geologist Laura Clor (right) and Rachel Teasdale (California State University – Chico, left) collect gas samples from a thermal feature at Sulphur Works in Lassen Volcanic National Park.
USGS geologist Deborah Bergfeld collects a gas sample from a superheated (hotter than the boiling point) fumarole in Little Hot Springs Valley at Lassen Volcanic National Park.
USGS geologist Deborah Bergfeld collects a gas sample from a superheated (hotter than the boiling point) fumarole in Little Hot Springs Valley at Lassen Volcanic National Park.

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.

Scientists collect volcanic gas data using a Fourier Transform Infrared spectrometer (FTIR). During the Kamoamoa eruption, sulfur dioxide emission rates from Kīlauea’s East Rift Zone reached the highest levels since the episodes of high-fountaining at Pu‘u‘ō‘ō (1983–1986) with an average rate of 8,500 tonnes per day and a peak value of 11,000 tonnes per day.
Scientists collect volcanic gas data using a Fourier Transform Infrared spectrometer (FTIR). During the Kamoamoa eruption, sulfur dioxide emission rates from Kīlauea’s East Rift Zone reached the highest levels since the episodes of high-fountaining at Pu‘u‘ō‘ō (1983–1986) with an average rate of 8,500 tonnes per day and a peak value of 11,000 tonnes per day.

Since the opening of the Overlook vent in Halema‘uma‘u Crater in 2008, FTIR spectroscopy has been used to monitor summit eruptive-gas composition. Infrared energy emitted by the lava lake surface (top left) is absorbed by gases present in the path between the instrument and the lak surface.
Since the opening of the Overlook vent in Halema‘uma‘u Crater in 2008, FTIR spectroscopy has been used to monitor summit eruptive-gas composition. Infrared energy emitted by the lava lake surface (top left) is absorbed by gases present in the path between the instrument and the lak surface.

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.

A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06. This photo was taken during a FLIR/maintenance flight on January 24, 2006.
A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06. This photo was taken during a FLIR/maintenance flight on January 24, 2006.
USGS geologists gathered samples by hand from vents on the dome and crater floor. Additionally, sulfur dioxide gas was measured from a specially equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano.
USGS geologists gathered samples by hand from vents on the dome and crater floor. Additionally, sulfur dioxide gas was measured from a specially equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano.
ARRA-funded student Taryn Lopez (Univ. Alaska-Fairbanks) sampling gas emissions at fumarole next to dome at the summit of Augustine volcano.
ARRA-funded student Taryn Lopez (Univ. Alaska-Fairbanks) sampling gas emissions at fumarole next to dome at the summit of Augustine volcano.
Kilauea's active summit vent is on the southeast side of Halema'uma'u Crater. In this photo, the floor of Halema'uma'u stretches out beyond the vent, and the summit of Kilauea Volcano is at upper right. The observation tower at the Hawaiian Volcano Observatory is the highest bump in the photo at Kilauea's summit.
Kilauea's active summit vent is on the southeast side of Halema'uma'u Crater. In this photo, the floor of Halema'uma'u stretches out beyond the vent, and the summit of Kilauea Volcano is at upper right. The observation tower at the Hawaiian Volcano Observatory is the highest bump in the photo at Kilauea's summit.