carbon monoxide poisoning

A United flight (UA-31) bound for Newark (New Jersey) from Munich (Germany) was safely diverted to London Heathrow Airport after multiple passengers complained of feeling lightheaded and unwell.
With the holiday season upon us and the palpable slow descent of the temperature, it seems appropriate to nestle in to the unpleasant notion that cold-related deaths are a reality.  An often avoidable one at that.