Hawaii Volcanic Gases and Ash

Vog pose a health hazard by aggravating preexisting respiratory ailments.
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 
Predicting the vog levels that visitors might experience during a short stay in Hawai`i is as difficult as predicting the weather.
The most critical factors that determine how much vog impacts an area are wind direction and speed.
According to June 2008 measurements of gas emissions from the two active vents on Kīlauea—Pu`u `Ō `ō (east rift) and Halema`uma`u (summit)—the combined total ranges from 2,000 to 4,000 tonnes (on average) of SO2 emitted from the volcano each day.
The sulfuric acid droplets in vog have the corrosive properties of dilute battery acid.
USGS Hawaiian Volcano Observatory geochemists use both remote and direct sampling techniques to measure compositions and emission rates of gas from Kīlauea Volcano.
As part of its mission to monitor eruptions and assess volcanic hazards, the U.S.
Ninety-nine percent of the gas molecules emitted during a volcanic eruption are water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2).