Final answer:
Emergency medical treatment should be initiated when a person who has ingested ethanol shows signs of severe alcohol poisoning. Seeking immediate medical help is crucial as alcohol poisoning can be life-threatening.
Step-by-step explanation:
Emergency medical treatment should be initiated for a person who has ingested ethanol when their blood alcohol concentration (BAC) is dangerously high or if they are exhibiting severe symptoms of alcohol poisoning. Signs of severe alcohol poisoning include unconsciousness, difficulty breathing, seizures, and vomiting. It is important to seek immediate medical help in these cases as alcohol poisoning can be life-threatening. Healthcare professionals can provide the necessary support and treatment, such as monitoring vital signs, administering intravenous fluids, and ensuring airway clearance.