Civil defense workers say the gas contains high levels of sulfur dioxide, which can make people choke.
The gas is especially harmful for elderly, young children and babies and people with respiratory problems, and may cause choking, the agency officials said Monday. Residents in the area and surrounding farm lots on Pohoiki Road near Lanipuna Gardens are advised the air quality is condition RED.
Authorities recommend leaving the area and seeking medical attention if severely affected.
"So far those explosions have not occurred and I think the key here is that the vent system is an open one, therefore pressure is not being built or developed down at the top of the lava column", Brantley told a conference call. Lava has destroyed more than 40 structures, including two dozen homes.
The booking pace for hotels and other activities, such as tours for lava viewing, zip lines and glass bottom boats have fallen 50 per cent.
The Big Island tourism board estimates $5 million worth of cancellations from May through July.
Tourism on the island brought in $2.5 billion in revenue past year.
This is the "first leak we're seeing out of the bucket", Birch said.
The National Weather Service has warned residents of "light ashfall" throughout the day in the island's southernmost district after a burst of volcanic emissions.
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Officials are concerned that a low voter turnout will undermine the credibility of the poll. Security forces have cordoned off the area for precautionary measures.
At least four new fissures have opened on Hawaii's Kilauea volcano this week, prompting more evacuations.
The rolling eruptions of Kilauea, which have caused hundreds of earthquakes, forced thousands of people in the nearby communities to evacuate.
"Be aware of the unpredictable nature of unsafe levels of SO2 gas because it can be carried far from the fissures with wind speed and direction", civil defence said in a Facebook post.
A separate fissure is still active after it formed on Sunday. No homes or roads were threatened by the flow.
Kilauea began erupting on May 3.
Almost 20 volcanic fissures have opened and are spewing lava and poisonous gas across the big island Tuesday morning.
Big Island authorities said the eruption effects just 10 percent of the island, so there's plenty to see and do without having to go near the red hot rivers of lava that continue to crawl their way out of fishers on the slopes of Kilauea.
And two more fissures opened yesterday, bring the total number to 19 and threatening to cut off vital escape routes for locals.
In this May 13, 2018 photo released by the U.S. Geological Survey, gases rise from a fissure near Pahoa, Hawaii.