 According to the Board , Grissom suffered severe third degree burns on over one @-@ third of his body and his spacesuit was mostly destroyed . White suffered third degree burns on almost half of his body and a quarter of his spacesuit had melted away . Chaffee suffered third degree burns over almost a quarter of his body and a small portion of his spacesuit was damaged . The autopsy report confirmed that the primary cause of death for all three astronauts was cardiac arrest caused by high concentrations of carbon monoxide . Burns suffered by the crew were not believed to be major factors , and it was concluded that most of them had occurred postmortem . <unk> happened after the fire melted the astronauts ' suits and oxygen tubes , exposing them to the lethal atmosphere of the cabin . 
