Could ventilation damage explain the casualties?

Could damage to the ventilation system have killed a large part of Sydney's crew?

The system was too divided for a single circulation fault to provide a simple explanation. Carbon monoxide entering air circuits could harm crew, but that remains hypothetical.

The ventilation system was divided into separate parts, limiting a simple explanation in which one circulation fault affected the whole ship. A later suggestion concerns carbon monoxide entering air circuits and poisoning crew. Poisoning is accepted as possible. It remains a hypothetical contribution to the casualties.