Quick thinking on the part of doctors at Children’s National Medical Center led to the rescue Tuesday morning of five members of a Fort Washington family who had carbon monoxide poisoning.

Doctors at the D.C. hospital were treating a young child, who also lived in the home, late Monday evening when they detected a high level of the gas in the child’s blood, officials said. After the hospital was unable to get in contact with the family, they alerted Prince George’s County Fire and EMS around 12:30 a.m. Tuesday.

Firefighters and EMS personnel arrived at the family’s home in the 8300 block of Bernard Drive and found that the five people inside — both parents and three children — were unconscious, officials said. Paramedics removed them from the house and began treating them before sending them by helicopter to a Baltimore hospital equipped with a hyperbaric chamber. Although all five had begun responding to treatment at the scene, they were listed in critical condition at the hospital.

Firefighters found that carbon monoxide levels in the home had reached 450 parts per million when they arrived at the scene. Anything above 5 parts per million is unhealthy. They discovered a natural gas furnace in the home was malfunctioning and likely produced the high levels of carbon monoxide.