Vog is air pollution caused by active volcanoes. The name comes from "volcanic smog." Volcanoes in Hawaii can emit sulfur dioxide into the atmosphere, where it reacts with oxygen, moisture, sunlight and particles in the air to form vog.
The most affected areas can change depending on volcanic activity, wind direction and weather. During typical trade wind patterns, emissions from Kilauea can move downwind across parts of the Big Island of Hawaii, including areas south and west of the volcano. When winds shift, vog can affect different districts and sometimes other islands.
In the past, gas plumes from Kilauea came from places such as Halema'uma'u Crater, Pu'u 'O'o and ocean-entry areas where lava flows reached the sea. Today, emission sources depend on current volcanic activity, which can change over time. Visitors and residents should check current volcano and air-quality updates during active eruption periods.
In general, the Big Island has higher vog levels than elsewhere, and the area around Kailua-Kona can be affected when winds carry volcanic emissions across the island. Areas from Volcano Village to Hilo can also experience vog or volcanic gas impacts depending on wind direction and eruption conditions.
Many people do not notice vog at low levels. It may appear as haze, reduced visibility or a grayish layer near the horizon. Vog can be noticeable when driving through or near Hawaii Volcanoes National Park, especially during active volcanic gas emissions.
Vog levels range from light to heavy. Some people are more sensitive to vog than others. Reactions can include eye, nose, throat or skin irritation, coughing, mucus buildup, headache, fatigue, dizziness, difficulty breathing or worsened asthma symptoms. Vog is especially a concern for people with asthma, COPD, heart disease or other respiratory conditions.
Vog conditions can change quickly because volcanic emissions, wind direction and weather patterns vary. Air-quality monitors and forecast models can help estimate conditions, but exact vog levels are difficult to predict far in advance.
For people who may be exposed to higher levels of vog, it can help to stay indoors, close windows and doors, avoid heavy outdoor activity, drink water and use air conditioning on recirculate mode if available. People with breathing or heart conditions should follow medical guidance and monitor local air-quality conditions during heavy vog days.
