Use of sulfuric acid instead of hydrofluoric acid at the Mobil Oil Corp. refinery in Torrance could pose less danger to area residents in the event of an accident, according to a preliminary report prepared by the Torrance city staff. But it also would mean a substantial increase in truck traffic and hazardous-waste disposal problems, the report says.

The report, requested by City Council members in the wake of a Nov. 24 explosion and fire at the Mobil refinery, suggests that “while both chemicals are potentially hazardous when used improperly, it is thought that hydrofluoric acid is much more dangerous.” When hydrofluoric acid comes into contact with air, it turns into lethal hydrogen fluoride gas.

The city staff has suggested that the council may want to consider hiring an outside consultant to assess the risks associated with continued use of hydrofluoric acid at the refinery as a catalyst to boost the octane of gasoline. Most other refineries in the South Bay use sulfuric acid.

Mobil announced in mid-December that the explosion was caused by an excess amount of hydrofluoric acid in a refinery unit that produces gasoline.

Four people were hurt in the explosion, but the tiny amount of hydrogen fluoride gas that was emitted into the atmosphere was not considered dangerous, investigators said.

After investigating the Mobil explosion, the South Coast Air Quality Management District staff called for the formation of a high-level multiagency task force to examine use of lethal chemicals at refineries and industrial plants throughout the Los Angeles metropolitan area.

The Torrance City Council endorsed the concept of a task force late Tuesday night. Mayor Katy Geissert told her colleagues the task force would be “a very useful source of information for us” and Torrance should seek representation on it.

The city’s staff report contains an extensive discussion about the danger posed by use of hydrofluoric acid at the refinery and suggests that a change to sulfuric acid might be safer in the event of an accident.

The report was presented to council members after published reports said the AQMD staff saw the possibility of a “significant release” of hydrogen fluoride gas at facilities that use the chemical.

Six facilities in the South Coast Air Basin handle or store hydrofluoric acid in significant quantities. In addition to the Mobil refinery, they are Allied Corp. in El Segundo, Union Pacific Resources in Wilmington. Powerine Co. and Golden West Refining Co. of Santa Fe Springs and Jones Co. of South Los Angeles.

The AQMD staff said that a significant release of the gas, caused by employee error, an earthquake, sabotage or some other scenario, could pose an “extreme and immediate health hazard to exposed citizens.”

The AQMD board will meet Friday in El Monte to consider the staff’s recommendation that the district “acknowledge the potential for a significant hydrogen fluoride release and the associated public health risk” and establish a task force to study transportation, storage and use of the chemical.