The gas is “an immediate threat to life for all who become exposed,” the Hawaii County Civil Defense Agency said in a statement.

Gaseous sulfur dioxide, which is colorless and smells like a burning match, can cause serious eye, nose and skin irritation as well as coughing, headaches and shortness of breath.

People with cardiovascular disease or respiratory ailments, such as asthma, are especially vulnerable. Older adults, infants and pregnant women are also particularly sensitive. No one knows the long-term health effects of exposure to volcanic sulfur dioxide, officials say.