Researchers found that Pluto's Gate was filled with volcanic CO₂, with concentrations around the shrine reaching as high as 80%, as noted by The Sun. The lethal gas forms a dense layer that coats the ...

The gate is built into one wall of a rectangular ... the Ploutonion was filled with volcanic carbon dioxide. Parts of the cave reached levels of 4% to 53% of volcanic carbon dioxide, depending ...

Gas coated the bottom of the cave at Pluto's Gate, forming a lethal lake particularly deadly to such animals. Strabo also noted that the priests who conducted rituals at the site seemed immune to ...