Some 3,000 residents in Japan’s Miyake-jima island must carry gas masks with them at all times as the mountains there constantly emit sulfuric gas, The Telegraph reported Tuesday.
Air raid sirens go off if there is a dramatic increase in the levels of sulphur in the air, the newspaper said.
The island, located 180 km from Tokyo, is dominated by Mount Oyama, an active volcano that has erupted several times in recent history.
Since its most recent eruption, there has been a constant flow of sulfuric gas coming from the mountain.