Final answer:
The immediate life threat to a conscious and alert fire victim with respiratory distress and signs of airway damage is airway swelling, which requires urgent medical care.
Step-by-step explanation:
The most immediate threat to the life of a person rescued from a burning house, who is conscious and alert but in considerable respiratory distress with a brassy cough and singed nasal hairs, is airway swelling. This condition can lead to a rapid and life-threatening closure of the airway, making it incredibly difficult for the victim to breathe. Immediate medical attention is necessary to manage the swelling and ensure that the patient maintains a clear airway to prevent asphyxiation.