Photo/Illutration The lid of an electric facility pit located in the Green World on the west side of the expo venue in Osaka’s Konohana Ward on April 7 (Shinnosuke Ito)

OSAKA—Potentially explosive methane gas was detected at the Osaka Expo venue here on April 6, one week before the event’s scheduled opening on April 13. 

The Japan Association for the 2025 World Exposition announced later that day that the gas had been detected around 4 p.m. in the Green World construction area on the west side of the venue.

At the time, a rehearsal was being conducted at the venue before the opening and visitors were present.

As a result of the gas, visitors were restricted from entering the area at 4:25 p.m. and the lid of an underground pit of an electric facility was opened for ventilation.

About an hour later, the association confirmed that the concentration of methane gas had fallen below the safety standard level and lifted the restriction. The rehearsal then resumed.

As the entire expo venue is reclaimed land, methane gas is generated in some areas due to the presence of waste and other materials buried in the land.

In March last year, sparks from the construction of toilets in the Green World area ignited methane gas, causing an explosion and fire.

The association took safety measures, such as installing ventilation equipment and gas detectors, as well as drilling holes in manholes to allow natural ventilation.

The association also continues to measure levels of gas concentrations and releases the results on a regular basis.

Despite the ventilation and monitoring precautionary measures, methane gas levels in the Green World area continued to be high during construction, including on April 6.

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