An ambulance's 18-minute delay Monday in arriving at a house in the city's Chevy Chase section, after which a patient suffering an asthma attack died, prompted D.C. Fire Chief Ray Alfred yesterday to alter the way the department responds to high-priority emergency calls.

Alfred said the new policy will require dispatchers to send a fire engine, an advanced life-support unit and a basic life-support unit to high-priority, or "code one" calls.

The former policy stated that only fire engines and advanced life support units be sent on such priority runs.

The advanced units have paramedics who can administer medicine and some sophisticated medical equipment.

Basic units don't have such equipment, and those aboard cannot administer medicine.

"Rather than take any chances, we'll send everything we have at code ones," Alfred said.

"We have a shortage of ambulances, so we've got to maximize the use of our resources.

"The current policy isn't working, so we're changing it," Alfred said.

Sheila Langevin, 58, died Monday night at Sibley Memorial Hospital of complications resulting from an asthma attack after the delay in the city ambulance reaching her house in the 3500 block of Rittenhouse Street NW.

Alfred also acknowledged that a mistake involving the department's new computer-aided dispatch system caused a Northeast woman to wait nearly two hours for an ambulance Tuesday night.

Alfred said that the fire department had launched an official investigation into both incidents to determine whether human error contributed to the delays.

In Monday's incident, firefighters trained as emergency medical technicians responded first to the scene, but had to wait for a basic ambulance because an advanced life support unit -- used for top priority calls -- was unavailable, Alfred said yesterday at a news conference.

Georges C. Benjamin, D.C. commissioner of public health and acting director of the Emergency Ambulance Bureau, said it would be speculation to say whether the new policy would have affected the outcome of Monday's incident.

Alfred said that Tuesday night's delay occurred when a computer error caused an ambulance to be sent to the 1600 block of P Street NW instead of to the 5000 block of Nash Street NE, where Zella Rempson was suffering abdominal pains.

Rempson eventually was taken to Georgetown University Hospital.

"It's apparent that there were indeed some errors in our equipment," Alfred said.

"We knew we would have some problems with a new system, and we're continuing to work on trying to debug that system," the chief said.