After rescuing a patient from a smoke-filled room, the most critical question to ask firefighters is:

Asking how long the patient was trapped in the room is crucial because it directly impacts the potential for smoke inhalation injury and overall exposure to toxic substances. The duration of time a patient spends in a smoke-filled environment can greatly influence their respiratory status and the severity of any injuries they may have sustained. Smoke inhalation can lead to complications such as hypoxia, carbon monoxide poisoning, and chemical burns to the respiratory system. Understanding the length of exposure allows the medical team to prioritize treatment, anticipate possible complications, and provide appropriate interventions, such as administering supplemental oxygen or preparing for airway management if necessary.

The other options, while valuable in assessing the overall situation, do not provide the same immediate and critical insight regarding the patient’s health status after being rescued. Knowing which materials were burning can help in understanding potential toxic exposures but does not give direct information about the patient's condition. Understanding how the fire started may assist in future prevention measures, but does not inform immediate patient care. The patient's breathing rate at the time of rescue is relevant but secondary to how long they were exposed to the harmful environment, as prolonged exposure could have caused significant damage regardless of their respiratory rate upon discovery.