# What gases are emitted by Kīlauea and other active volcanoes?

Ninety-nine percent of the gas molecules emitted during a volcanic eruption are water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2). The remaining one percent is comprised of small amounts of hydrogen sulfide, carbon monoxide, hydrogen chloride, hydrogen fluoride, and other minor gas species.

Learn more: Volcanic Gas

## Related Content

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### Does vog (volcanic smog) impact plants and animals?

The sulfuric acid droplets in vog have the corrosive properties of dilute battery acid. When vog mixes directly with moisture on the leaves of plants it can cause severe chemical burns, which can damage or kill the plants. Sulfur dioxide (SO2) gas can also diffuse through leaves and dissolve to form acidic conditions within plant tissue. Farmers...

### 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...

### Where and how do sulfur dioxide and volcanic gases (vog) affect air quality in Hawaii?

The most critical factors that determine how much vog impacts an area are wind direction and speed. Air temperature, humidity, rainfall, location of the source, and the amount of sulfur dioxide (SO2) being emitted are also factors. During prevailing trade (from northeast) wind conditions, any SO2 emitted from Puu Ōō is blown out to sea, while...

### Should I cancel my plans to visit to Hawaii Island because of sulfur dioxide (SO2) and vog?

Predicting the vog levels that visitors might experience during a short stay in Hawaii is as difficult as predicting the weather. Once volcanic emissions are in the atmosphere, they are distributed by prevailing winds. Where and how bad the vog is ultimately depends on several factors including wind direction, wind speed, air temperature,...

### What health hazards are posed by vog (volcanic smog)?

Vog poses a health hazard by aggravating preexisting respiratory ailments. Sulfur dioxide (SO2) gas can irritate skin and the tissues and mucous membranes of the eyes, nose, and throat, and can penetrate airways, producing respiratory distress in some individuals. Aerosol particles in vog can also penetrate deep into human lungs and, at elevated...

### What is "vog"? How is it related to sulfur dioxide (SO2) emissions?

Vog (volcanic smog) is a visible haze comprised of gas and an aerosol of tiny particles and acidic droplets created when sulfur dioxide (SO2) and other gases emitted from a volcano chemically interact with sunlight and atmospheric oxygen, moisture, and dust. Volcanic gas emissions can pose environmental and health risks to nearby communities. Vog...

### Does ash ever erupt from Kīlauea Volcano?

Kīlauea Volcano is renowned for its relatively benign eruptions of fluid lava flows. Therefore, many people were surprised by the small explosions that occurred in Halemaumau Crater in 2008 and 2018, and even more surprised to learn that volcanic ash was being erupted from a new gas vent. However, ash emissions from Halemaumau Crater are part...

### Why is it important to monitor volcanoes?

The United States and its territories contain 169 geologically active volcanoes, of which 54 volcanoes are a high threat or very high threat to public safety. Many of these volcanoes have erupted in the recent past and will erupt again in the foreseeable future. As populations increase, areas near volcanoes are being developed and aviation routes...

### 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...

### Is it dangerous to work on volcanoes? What precautions do scientists take?

Volcanoes are inherently beautiful places where forces of nature combine to produce awesome events and spectacular landscapes. For volcanologists, they're FUN to work on! Safety is, however, always the primary concern because volcanoes can be dangerous places. USGS scientists try hard to understand the risk inherent in any situation, then train...
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Date published: May 6, 2019

### The National Volcano Early Warning System (NVEWS) will help USGS better monitor nation’s most dangerous volcanoes

In September 2004, USGS scientists detected sudden, but unmistakable, signs that Mount St. Helens was waking up. Volcano monitors had picked up the occurrence of hundreds of small earthquakes and other signals that the volcano’s crater floor had begun to rise. Within a week, several eruptions blasted clouds of ash into the atmosphere, and soon after, a new lava dome emerged in the crater.

Date published: June 21, 2018

### Kīlauea Volcano Erupts

Today's update for June 21st, 2018 will be the last of the daily updates on this USGS feature story.  We encourage you to keep checking the USGS Hawaiian Volcano Observatory (HVO) Kīlauea status website for daily activity updates. You can also visit the USGS Facebook page and the USGS Twitter feed as updates become available. For press inquiries, please email volcanomedia@usgs.gov.

Date published: May 18, 2017

### EarthWord–Vog

Just like smog and fog, this EarthWord is not what you want to see while driving...

Date published: August 18, 2016

### Living with Vog on an Active Volcano: New Resources

New informational products about the health hazards of volcanic air pollution known as “vog,” are available through a new interagency partnership.

Date published: October 5, 2015

### EarthWord: Fumarole

Fumaroles are openings in the earth’s surface that emit steam and volcanic gases, such as sulfur dioxide and carbon dioxide. They can occur as holes, cracks, or fissures near active volcanoes or in areas where magma has risen into the earth’s crust without erupting. A fumarole can vent for centuries or quickly go extinct, depending on the longevity of its heat source.

Date published: February 11, 2015

### New Study Looks at How People Cope with Vog

A new study to examine how people who live downwind of Kīlauea Volcano cope with volcanic gas emissions, or vog, is currently underway.

Date published: January 27, 2012

### Kilauea’s Volcanic Gases and Their Environmental Impacts

U.S. Geological Survey Hawaiian Volcano Observatory scientists Jeff Sutton and Tamar Elias will update information on Kīlauea Volcano’s gas emissions and associated environmental impacts.  Their presentation will be at the park’s Kīlauea Visitor Center Auditorium. Park entrance fees apply.

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August 30, 2018

### PubTalk 8/2018 — What on Earth is going on at Kilauea Volcano?

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
August 16, 2016

### USGS HVO geochemist measuring gases released from Kīlauea Volcano

USGS Hawaiian Volcano Observatory geochemist measuring gases released from Kïlauea with a Fourier transform infrared (FTIR) spectrometer, an instrument that detects gas compositions on the basis of absorbed infrared light. The data obtained from FTIR measurements have been useful in identifying the many components of volcanic-gas emissions, which provide information on the

...
August 16, 2016

### Gas plume from Halemaʻumaʻu Crater, Kilauea Volcano

With stagnant winds present, the plume from Halemauma`u Crater at the summit of Kilauea Volcano, stands straight up, showing off the distant, but bright, full moon.

July 27, 2016

### Active lava lake at summit of Kīlauea volcano

Aerial photograph of active lava lake in Hale maʻumaʻu Crater at the summit of Kīlauea volcano.

April 14, 2016

### Fumarole on Kīlauea Volcano, Hawaiʻi

Fumarole on Kīlauea Volcano, Hawaiʻi. Elemental sulfur vapor escaping from the fumarole has cooled to form yellow-colored crystals around its margins. Credit: Robert L. Christiansen.

http://volcanoes.usgs.gov/vsc/glossary/fumarole.html

March 15, 2016

### Collecting Gas Sample at a Fumarole

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.

March 15, 2016

### Collecting Gas at a Boiling Pool

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.

May 31, 2014

### Monitoring Volcanic Gases on Kilauea's East Rift Zone II

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. Instrumentation at this site measures ambient concentration of noxious sulfur dioxide gas released from the volcano's vents, along with

...
May 31, 2014

### Monitoring Volcanic Gases on Kilauea's East Rift Zone

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. Instrumentation at this site measures ambient concentration of noxious sulfur dioxide gas released from the volcano's vents, along with meteorological

...
July 9, 2011

### Collecting Volcanic Gas Samples

Steven Ingebritsen (lower right, in blue hat) kneels in the warm mud as he collects samples of the gases emitted from the fumaroles on the north side of Crater Rock on Mount Hood. The samples are taken back to the laboratory for an analysis of the gases' chemical composition. By routinely collecting gas samples and comparing their composition to past measurements,

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July 6, 2011

### Volcanic Gas Sampling

Christoph Kern acquires ultraviolet images of volcanic gas over the dome and crater of Mount St. Helens. Although practically invisible to the human eye, sulfur dioxide absorbs ultraviolet light and appears dark in images captured by the equipment. Sulfur dioxide is typically emitted from magma as it approaches the surface, so surveys are conducted on a regular basis at

...
June 30, 2011

### The Air We Breathe…It’s a Gas!

We live at the bottom of an ocean of air. Most adults take around 29,000 breaths a day, children breathe a little faster; but what is in this air we breathe? What are the gases in the air? How much of each gas is there? Do these gases have different weights? How cold are liquid nitrogen and dry ice, and where did those names come from? Come join us to explore these