Two lawsuits seeking a total of $1 million in damages blame the death of a 6-year-old boy and the injury of a 17-year-old youth in a Herndon apartment fire on a smoke detector the suits claim was defective.

One suit, filed on behalf of the boy, James A. Catlin, by his guardian, William M. Brill, claims the smoke detector failed to sound an alarm that would have awakened the other occupants of the Elden Terrace apartment so they could have saved the child.

Roy D. Hayden, who was then 17 years old and who lived in the apartment, said in the second suit that he was sleeping when the March 7, 1984, fire broke out and was forced to "flee for his life out a broken window." He maintains that the smoke detector failed to awaken him in time to escape without injury.

The suits, which were filed in Fairfax County Circuit Court and which each seek $500,000 plus costs, were filed against the manager and owner of the Elden Terrace Apartments, 1060 Alabama Dr., and those involved in the design, production and sale of the smoke detector known as Sentinel Pyrotector. The suit says the apartment manager and owner should have warned tenants of any potential dangers on the premises.

Lt. Leonard Murry, spokesman for the fire department, said yesterday that in addition to Hayden, Effie Blanton, 80, a resident of another apartment, and Loretta Russell, 24, were injured in the blaze. Robert D. Dain, the attorney in both suits, said also injured were Michael Brill, 11 months, Michelle Brill, 4, and Melissa Hedrick, age unknown.

Murry said there were two fires, one in the kitchen and one in the living room, and that they were determined to have been accidentally set by children playing with matches. Murry said the smoke detector in the garden-style apartment was sent to a lab but was too badly damaged to determine whether it had worked.

Fairfax County law requires apartment building owners to install and maintain smoke detectors, Murry said.

Hayden's lawsuit claims that among other things he has suffered severe burns, excruciating pain and permanent scarring and disfigurement.

One of the general partners of Dulles Park Associates Limited Partnership, a defendant in the suits, said the firm had not yet received a copy of the suits and could not comment. The other defendants, who could not be reached for comment, are JBG Properties Inc., Grinnell Fire Protection Systems Company Inc., Chloride Inc., Chloride Pyrotector and Pyrotector Inc.