The three were found unconscious in the basement of the semiconductor factory in Suwon only south of Seoul, the firm said in a statement.
A man aged 24 was pronounced dead in hospital hours later and two others, aged 26 and 54, stay unconscious, Samsung said.
All were employees of one of Samsung’s providers and were scrutinizing the factory’s gas-related facilities, it included.
“It is believed that the reason for death is suffocation due to a carbon dioxide leak,” Samsung said, adding it was investigating.
Samsung – the world’s leading manufacturer of smartphones in addition to memory chips – operates a vast semiconductor manufacturing chemical in Suwon.
Fatal accidents in major businesses have made frequent headlines from the South, which has fought to enhance poor safety standards in factories.
In January four employees suffocated because of a gas leak at a steel mill owned by Posco – the country’s top steelmaker – in the southern city of Pohang.
In August a year four employees died when a fuel tank exploded in a vessel under construction in the headquarters of STX Offshore and Shipbuilding in the southern city of Changwon.