20 July 2004: Having Too Much and Too Little Oxygen on the Space Station, SpaceRef
“Several Russian Progress spacecraft were allowed to reenter Earth’s atmosphere in 2003 carrying unused oxygen supplies. In one case, half of the oxygen being delivered to the ISS was dumped into the Pacific Ocean when these Progress spacecraft later reentered the Earth’s atmosphere. Within months the ISS would face the prospect of a shortfall in oxygen supplies – and contingency scenarios, which included leaving the ISS, unmanned as an option.”
