They had a barrel tile roof, boxed eaves, brick and stucco siding. They had just cut down three trees near their house and cleaned out the rain gutters. And a wide street and a line of other large luxury homes separated their Yorba Linda property from the brush wild lands of Chino Hills State Park.
But their hearts sank when they turned onto their block Sunday afternoon. Of the 18 homes on their side of the street, only two had burned. One was theirs.
"I'm glad that my neighbors' houses survived," said Hamlet Haroutounian, 47.
"But it bothers me: Why my house?"
The answer was something they never thought of: the humble attic vent.
"An ember settled right there and got into the insulation," said Capt. Bill Lockhart of the Orange County Fire Authority, pointing to the gable vent on a still-standing wall. "I can guarantee it. It's almost out of a textbook."
He said the mesh covering the vent had quarter-inch holes. Fire marshals now recommend eighth-inch mesh.
For 50 years, fire authorities have told homeowners in fire-prone areas to get rid of shake roofs and to clear brush, and people have gradually heeded the advice.
These days, the devil is hidden in the smallest of details.
"There will be a weak link in the house that is destroyed," said Stephen Quarles, an advisor at UC Cooperative Extension and an expert in how homes catch fire.
He said it is usually not raging flames that ignite a home, but an ember slipping through a small breach: a vent, a doggie door, a gap under the garage door, an open window, a cracked roof tile.
Fires like the one that raged through north Orange County last weekend, destroying 113 homes in Yorba Linda, spew billions of embers into the air -- some as small as an apple seed. Santa Ana winds drive those burning projectiles horizontally for hundreds of yards, pelting homes far from the flame front. Just one ember getting through a crack could spell destruction.
"The biggest thing that causes these homes to burn is ember intrusion," said Chip Prather, chief of the Orange County Fire Authority. "You've got hurricane-force winds pushing embers toward houses."
The goal is to seal off the home like a ship to the sea and prepare for a leak where it is most likely to occur.
People don't think of the newspapers awaiting recycling in their garage, or old boxes in the attic, or dried-up birds' nests in the arches of roof tiles.
State rules in effect since July 1 are meant to address this. Builders in fire-prone areas are required to screen attic vents, cover eaves, use non-flammable planks for decks, install tempered glass in windows so they don't shatter when heated and close the gaps under barrel tiles with mortar or a piece of material called a bird stop.
The rules do not require homeowners to update existing homes. And even compliance with the new code doesn't guarantee safety.
Wood mulch, patio furniture and trash cans ignite next to the house. Wind pushes piles of burning debris against doorjambs.