Southern California Gas officials said Friday that they will hire a private contractor to conduct indoor air screening at a sampling of homes in the Porter Ranch area, near the recently plugged gas leak at Aliso Canyon.
The company agreed to pay for the testing at the request of county Supervisor Michael D. Antonovich, who represents the area.
The testing will be overseen by the county Department of Public Health.
The company will test 75 homes from a randomly selected pool of residents. The screenings are scheduled to begin Monday.
The screening, under the direction of a California registered professional engineer, will use a flame ionization detector to look for methane, and Tedlar bags to capture indoor air "grab samples," the gas company said.
The contractor will also screen for mercaptans, additives that give natural gas its rotten-egg-like smell, and which have been blamed for a range of health effects suffered by people living near the leak.
They reported symptoms including nausea, headaches and nosebleeds. Many residents who had been temporarily relocated while the leak was ongoing returned home after it was plugged on Feb. 18, and reported the symptoms had stopped.
But some have continued to report health effects.
The gas company has generally maintained that air levels have returned to normal and that it is safe for residents to return home.
Gillian Wright, vice president of customer services for the company, said in a statement: "We strongly believe that our customers and neighbors in Porter Ranch deserve peace of mind in knowing the air is normal and we are taking action to enable a smooth transition back to their homes and neighborhoods."
Antonovich's chief of staff, Kathryn Barger, said county supervisors had asked for an independent contractor to do the testing because some residents had expressed concerns about the objectivity of the health department.
"We felt that having an independent contractor gives credibility" in the eyes of residents, she said, "even though we feel that Public Health is credible."
Barger said that based on the testing results, the county might seek another extension of a court order that forces the gas company to pay for residents who fled the leak to stay in hotels.
The relocation period was originally slated to end eight days after the leak was plugged, but the county went to court to seek an extension. As a result, the period was extended through March 18.
Paula Cracium, president of the Porter Ranch Neighborhood Council, praised the plan to test air inside of homes.
"Families want to come home, but to a safe home and this will help give them the assurance their homes are safe and help us begin rebuilding our community," she said in a statement.