Authorities Say Clogged Heater Killed 2 Children : Safety: Their parents remain in serious condition. Another family of four that was in the house is OK.

For 16 hours, the clogged heater spewed carbon monoxide into the house, silently filling it with deadly fumes. Unaware of the danger, two families slept groggily on, four adults and four children slowly being suffocated.

Finally, about 6 p.m. Saturday, the phone rang at the East 3rd Street home of Gustavo and Zoila Alvarez. It was a neighbor who wanted to chat. Stupefied by the odorless gas, the Alvarezes and their two children had been asleep all day.

The Alvarezes were dazed and sick but alive. Their guests were not as lucky. The parents were revived, but their two children were dead.

Authorities declined Sunday to release the names of the second family. But members of the Alvarez family identified them as Edgar Hernex, 26; his wife Miriam, 23; and their children, Alexandra, 3, and Brian, 6 months, all of Westchester.

A Southern California Gas Co. spokeswoman said a clogged wall furnace led to the children’s deaths. The heater was located in a hall outside the bedroom where all four Hernexes were sleeping.

“It was a clogged vent and flue. There was a lot of lint and dirt in the furnace. It obviously was not serviced in a long time,” spokeswoman Denise King said.

A spokeswoman for the Los Angeles County Sheriff’s Department said the incident has been classified as accidental.

The Alvarezes and Edgar and Miriam Hernex were treated for carbon monoxide poisoning in a decompression chamber at Northridge Hospital Medical Center. The Alvarez family was later released, but the Hernexes remained at the hospital in serious condition.

In an interview outside her modest, yellow-stucco home Sunday, a somber Zoila Alvarez said her family and the Hernexes had gone to church together late Friday night and returned to the Alvarez home about 1:30 a.m. Saturday. They had coffee, turned on the wall heater and went to bed.

Alvarez, 42, who cleans houses for a living, said her husband, 36, grew up in Guatemala with Edgar Hernex, a furniture deliveryman. The two families, who often attend church together in South-Central Los Angeles, planned to spend the long Thanksgiving holiday in Palmdale, she said.

But with the faulty heater releasing what a gas company official said was a massive amount of carbon monoxide, no one in the house woke up until about 6 p.m. Saturday, when a neighbor, Maria Escobar, telephoned Zoila Alvarez.

“She said, ‘Come on over, because we’re sick,’ ” Escobar said. “When I came in, it was a surprise. Because everybody was real sick.

“They lost track of time. They didn’t know.”

Alvarez said her 6-year-old son, Gus, was so disoriented by the gas that he kept falling down.

Alvarez told her husband that she felt sick and wanted to go to a doctor. He told her to go check on the Hernexes. When she entered their room, she saw that Edgar Hernex had vomited without awakening.

The Alvarezes’ 11-year-old daughter, Annie, said she went into the room with her parents to try and awaken the Hernex family.

“My dad told us to wake everyone up,” she said. “But when we went in there, they wouldn’t wake up. We gave them 7-Up and everything.”

The Alvarezes called 911 about 7 p.m., telling a dispatcher that they felt nauseous and had respiratory problems. Paramedics later arrived and the Hernex children were pronounced dead at the scene.

Willie Perkins, another neighbor, said he saw a number of people stumble out of the house, gagging and coughing.

King, the gas company spokeswoman, said that because the heater’s vent was clogged, exhaust gases were forced back into the burner, where they formed deadly carbon monoxide that was then released into the house.

Times staff writer Chip Johnson contributed to this story.