Today, at around 16:00, the Osaka Fire Department was informed that a methane gas concentration exceeding 5 vol%* was detected in the Green World (GW) construction area.
In response, staff from the Konohana Fire Station and the Association measured the gas concentration in the underground pit for outdoor electrical equipment where methane gas was reported to have been detected and found the methane gas concentration exceeded 5 vol%.
With the above information, access to the area was restricted to visitors, etc. at 16:25 and the lid of the underground pit for electrical equipment was opened for natural ventilation. The restriction was lifted after it was confirmed that the measured value was below the standard value. It was subsequently confirmed that the measured value was 0 vol%. Following measurements in the underground pit in question, measurements were also taken at the other underground pits in GW and all were found to be below the standard value, confirming that they were safe.
The underground pit for electrical equipment in the area where methane gas concentration above the standard value was detected today is being continuously monitored, as values above the standard value have been detected in the past, and natural ventilation has been provided by opening the lid during construction. Countermeasures have been put in place for during the Expo period, such as replacing the perforated lids and taking measures to prevent gas ingress. As a result of these measures, the concentration on the morning of 6 April was measured to be 0 vol%.
In the future, as the concentration in the affected area may temporarily increase as in this incident, we will increase the frequency of monitoring and keep the lid open at all times to allow for better ventilation and maintain low concentrations. At the same time, a fence will be installed around the area to prevent people from entering. In addition, the frequency of monitoring of underground pits in the vicinity of the GW area will be increased and measures ensuring appropriate action will be taken.
The Association will continue to manage the Expo site to ensure that visitors can come with peace of mind.
*The standard value specified in the Ordnance on Industrial Safety and Health is 1.5 vol%. The lower explosive limit for methane gas is 5 vol%.
