USGS
Hawaiian Volcano Observatory

Frequently Asked Questions about Air Quality in Hawai`i

14. What can I do to minimize the risk of exposure to SO2 and vog?
To minimize potential health hazards of SO2 and vog, the Hawai`i State Department of Health and the American Lung Association of Hawai`i recommend the following protective actions.

During times of poor air quality due to SO2 or vog, people—particularly asthmatic children and other sensitive individuals with preexisting respiratory conditions, such as asthma, emphysema, bronchitis, and chronic lung or heart disease—should (1) stay indoors and use an air conditioner if possible; (2) close doors and windows to reduce the flow of outdoor air into homes; (3) limit outdoor activities; (4) avoid outdoor physical exertion; (5) contact a doctor as soon as possible if any respiratory symptoms develop; (6) keep medications on hand and readily available; and (7) drink plenty of liquids.

Civil Defense SO2 warning sign on the road. People living in areas impacted by heavy SO2 and vog should also heed advisories from the Hawai`i County Civil Defense, the agency responsible for public safety. In addition to its Web site and radio broadcasts, Civil Defense disseminates information through field units and road signs.

15. Where can I find current information and data about air quality in Hawai`i?
Air quality information and data for Hawai`i is available through Web sites created by the Hawai`i State Department of Health (DOH), National Park Service/USGS Hawaiian Volcano Observatory (NPS/HVO), U.S. Environmental Protection Agency (EPA), and Hawai`i County Civil Defense. Forecasts for weather and wind conditions, which affect vog dispersal, can be found on the University of Hawai`i Web site.

Current SO2 Conditions, Kilauea Summit

16. Should I cancel my plans to visit to Hawai`i Island because of SO2 and vog?
Predicting the vog levels that visitors might experience during a short stay in Hawai`i is as difficult as predicting the weather. Once volcanic emissions are in the atmosphere, they are distributed by prevailing winds. Trade, or northeasterly, winds are dominant 80-90% of the time during the summer and produce poor air quality on the southern and western sides of the island. The east or windward side is more likely to experience poor air quality during trade wind interruptions, which occur more frequently during the winter months. Where and how bad the vog is ultimately depends on several factors besides wind direction and wind speed including air temperature, humidity, and rainfall as well as the location of the source and amount of SO2 being emitted from Kīlauea Volcano.

For normally healthy people, the level of vog typically experienced during trade wind conditions along the Kona coast on Hawai`i Island—especially for short-term exposures such as a week of vacation—can be more annoying than life-threatening. However, if you have existing heart and/or respiratory ailments or other conditions that compromise your physical health, or if you are pregnant, you should check with your personal physician for advice about traveling to any location with poor air quality.

If vog reaches levels that are potentially hazardous to human health, the Hawai`i County Civil Defense issues advisories via their Web site and radio broadcasts and, if necessary, calls for voluntary or mandatory evacuations. To protect your health, take heed of all advisories released by Civil Defense and other relevant emergency management agencies.

Gas emissions at Halema`uma`u Crater Whether or not you should cancel your trip to Hawai`i Island is a personal decision that only you can make. To help you make an informed decision, information about vog and air quality in Hawai`i is provided in the Frequently Asked Questions above. You can also see the volcanic gas plumes and air quality conditions for yourself on local Webcams.

17. How do other communities near active volcanoes deal with SO2 emissions?
In any given year, there are 50-70 volcanic eruptions around the world, during which water vapor (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), and other gases are released. Many volcanoes also emit gases between eruptions. The impact of these gases depends on the duration of the eruption, the proximity of the volcano to populated areas, and wind speed and direction.

Examples of volcanoes that have adversely affected people due to persistent SO2 emissions include Nyiragongo (DR Congo); Masaya (Nicaragua); Poas (Costa Rica); and Miyakejima, Aso, and Sakurajima (Japan). Information about the impacts of these and other volcanoes around the world can be found in the links below.

18. What is volcanic ash?
Volcanic ash is formed during explosive volcanic eruptions when gases dissolved in magma (molten rock) expand and escape violently into the air, or when water is heated by magma and abruptly flashes into steam. The force of escaping gas shatters solid rocks. Expanding gas also shreds magma, blasting it into the air, where it solidifies into fragments of volcanic glass.

Volcanic ash erupted from Kilauea on March 24, 2008 Tephra is the general term for volcanic rock fragments exploded or carried into the air during an eruption. Such fragments can range in size from less than 2 mm (0.08 inches) to more than 1 m (3.2 feet) in diameter. The smallest tephra is called volcanic ash, pieces of pulverized rock and volcanic glass the size of sand or silt. Tiny ash particles can be less than 0.001 mm (0.00004 inches) in diameter.

Volcanic ash can be carried great distances by wind, unlike larger tephra, which typically falls back to the ground at or near the vent. Thus, ash can cover a much larger area and disrupt the lives of far more people than other tephra.

Volcanic ash from Halema`uma`u gas plume on April 3, 2008. Volcanic ash is not the product of combustion, like the soft, fluffy material created by burning wood, leaves, or paper. Volcanic ash is hard and does not dissolve in water. It is also extremely abrasive and mildly corrosive.

The volcanic ash produced by Kīlauea 's small explosions in March and April 2008, and still erupting from Halema`uma`u Crater's new vent, is a mixture of lithic fragments (pulverized rock) and tiny spheres and shards of volcanic glass, including Pele's hair and Pele's tears.

19. Is this the first time Kīlauea has erupted volcanic ash?
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 Halema`uma`u Crater in March and April 2008—and even more surprised to learn that volcanic ash is being erupted from the new gas vent. However, ash emissions from Halema`uma`u Crater are part of the volcano's legacy.

Halema`uma`u Explosion
on May 13, 1924. Kīlauea 's summit has erupted explosively throughout the history of the volcano, producing ash deposits that date back at least 30,000 years—and probably older. In 1790, at least 80 people were killed in the Ka`ū Desert by searing hot gas and ash produced by a devastating explosion. More recently, in 1924, a series of steam explosions in Halema`uma`u Crater blasted columns of volcanic ash and dust as high as two miles (3 km) into the air. These plumes were blown downwind beyond the community of Pahala, 32 km (20 miles) away, where ash fallout turned day into night. Muddy ash also fell in lower Puna, making railroad tracks so slippery that trains couldn't travel in Maku`u. One person was killed near Halema`uma`u when he ventured too close to the vent and was hit by falling rocks.

As you can see, 2008 is not the first time that volcanic ash has erupted from Kīlauea , and it almost certainly won't be the last.

20. Who monitors ashfall in Hawai`i?
For the past three months (as of June 2008), scientists at the USGS Hawaiian Volcano Observatory (HVO) have been taking daily measurements to determine the amount of ash falling from the gas plume at Kīlauea 's summit.

Wooden boxes and plastic buckets strategically placed on the rim of Halema`uma`u Crater collect ash  as it falls from the plume. Each morning, rain or shine, HVO scientists go to the rim of Halema`uma`u Crater downwind of the gas vent to collect ash that has fallen from the plume during the past 24 hours. The ash is taken back to HVO, where it is weighed to calculate its average accumulation rate and inspected under a microscope to determine its composition—lithic fragments (pulverized rock), volcanic glass, or a combination of both. The glass component of the ash is then sent to colleagues at the USGS Cascade Volcano Observatory for chemical and petrographic analyses.

21. How much ash is Kīlauea currently erupting?
On March 24, 2008, just 12 days after the new vent opened in Halema`uma`u Crater, the gas plume turned a dusty-brown color, indicating that it contained an abundance of volcanic ash. Virtually all of this ash fell to the ground near the vent, but there were reports of thin "dustings of grit" on parked vehicles in Hawaiian Ocean View Estates, 60 km (38 miles) from Kīlauea 's summit.

Ash-rich Halema`uma`u plume on March 24, 2008. Since the appearance of the ash-rich plume in March, which resulted in the highest ash deposition rate measured thus far, volcanic ash emissions from Kīlauea have declined. Even at their highest, recent ash emissions are minuscule—less than from any known explosive eruption at Kīlauea. As of June 2008, volcanic ash raining from the Halema`uma`u gas plume remains tiny—both in size and amount—and rarely reaches areas beyond the boundaries of Hawai`i Volcanoes National Park.

22. Does volcanic ash pose hazards to human health?
Like airborne particles from dust storms, forest fires, and air pollution, volcanic ash is often small enough (less than 10 microns) to be inhaled deeply into the lungs. Thus, volcanic ash poses a health risk, especially to children, elderly people, and individuals with cardiac or respiratory ailments, such as asthma, chronic bronchitis, and emphysema.
23. What other hazards are associated with volcanic ash?
Heavy ash fall can collapse roofs, cause short circuits and damage in electronic components, interrupt telephone and radio communications, cause power outages, clog air filters in vehicles and machinery, create poor visibility, make roads slippery or impassable, damage crops, and cause harm to grazing livestock. HVO vehicle leaves tracks in a thin layer of ash blanketing Crater Rim Drive after the April 16, 2008, explosion.

Airborne volcanic ash poses a serious hazard to aviation because it can diminish visibility, damage flight control systems, and cause jet engines to fail. The greatest danger is to aircraft flying near an ash plume, but winds can blow volcanic ash great distances, so it can also pose a hazard to aircraft far from an erupting volcano.

On March 25, at the request of Hawai`i Volcanoes National Park, the Federal Aviation Administration closed the airspace at or below 4,000 feet above ground level and three nautical miles from Halema`uma`u Crater to minimize risks to aircraft flying near the summit of Kīlauea. Because tiny amounts of ash continue to fall from the plume, airspace above Halema`uma`u remains closed as of June 2008.

24. What can I do to minimize the impacts of volcanic ash?
As with any natural disaster, communities and homeowners should develop an emergency-response plan that can be activated if Kīlauea spews volcanic ash. Having a plan in place before an eruption occurs can greatly reduce the harmful and disruptive effects of ash.

Heavy ash fall is not expected from Kīlauea's current summit eruption, but even small amounts of ash can be problematic to humans, animals, and plants. Web sites listed below provide helpful suggestions on how to prepare for, and contend with, ash fallout.


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Updated: 18 December 2012 (pnf)