Photo/Illutration An actor re-enacts the scene of a fatal carbon dioxide poisoning caused by dry ice placed in a coffin. (Provided by the National Consumer Affairs Center of Japan)

Authorities are warning of accidental carbon dioxide poisoning from dry ice used to keep coffins cool at funerals and urge mourners not to lean their heads into them while saying goodbye to deceased loved ones.

Between 2020 and 2021, three deaths were reportedly caused by CO2 gas produced by dry ice within coffins. These deaths were reported in Miyagi, Miyazaki and Okinawa prefectures, according to the Consumer Affairs Agency.

In two of the cases, the mourners were found motionless with their heads still in the coffins while the third victim was lying on the floor by a coffin that had a small window in its lid left open.

A possible factor behind these accidents is that people are not aware of the dangers of CO2 poisoning, according to the Consumer Affairs Agency. Additionally, since funerals are special events uncommon in daily life, most people are not thinking about dry ice evaporating within a casket.

The National Consumer Affairs Center of Japan conducted an experiment to reconstruct the accident scenes, using a coffin containing a manikin and 10 kilograms of dry ice.

In 20 minutes, CO2 concentration within the closed casket reached 30 percent, high enough to knock a person unconscious in seconds. Four hours into the experiment, CO2 concentration plateaued at around 90 percent.

When the coffin was opened, the CO2 levels immediately dropped to around 60 percent.

However, they remained above 30 percent even after the coffin was left open for 50 minutes. This is likely because carbon dioxide gas, which is denser and heavier than air, will sink to the bottom of the coffin rather than rise into the air and disperse.

Both organizations warn mourners to ventilate the room properly during a funeral wake and avoid leaving anyone alone by the coffin.

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