Reports that a dozen autos here and hundreds across the country have caught on fire recently due to heat produced by their catalytic converters have provoked new concern about the devices' safety among federal and local fire officials.
Most of the fires in the Washington area were ignited when heat from the converters caused piles of dry leaves beneath parked cars to burst into flame.
Elsewhere, there have been hundreds of reports of auto fires traceable to the converters. In Hartford, Conn., three cruising patrol cars burst into flames last spring when the hot converters corroded metal floorboard plates and ignited interior carpeting, police officials there said yesterday.
Although no injuries were reported in the fires, consumer auto safety advocates promptly called for tougher federal safety requirements and renewed investigation of possible hazards from using the devices.
"A general review is in order," said Clarence Ditlow, director of the Center for Auto Safety, a consumer organization founded by Ralph Nader. Ditlow said the remedy could be as inexpensive and as simple as "a few cents' worth of additional insulation" in exhaust systems.
Catalytic converters are the auto industry's major response to federal antipollution requirements. Most U.S. cars made since 1975 are equipped with the converters, which in effect burn up pollutants before they are released into the air. Foreign manufacturers initially relied on other antipollution methods have increasingly switched to the converters.
The last foreign-make holdouts, such as Subaru and BMW, are expected to switch to the converters soon.
The concern about the converter's safety represents the latest development in a controversy dating back more than four years. An estimated 500 reports of fires traced to converters were filed with the National Highway Traffic Safety Administration in 1975, prompting that agency to open a two-year review of the incidents.
After that review, the agency decided that the potential fire risk from converters was within acceptable limits. Its conclusion was that the "rate and the nature of catalytic converter incidents do not present an unreasonable risk of death or injury to the public."
Since then the agency has received 37 complaints about the converters, a spokesman, Robert Boaz, said yesterday. He said that wasn't enough to warrant another investigation.
However, he said the agency, if formally asked to reopen a file on the converters would decide within the required 120 days whether to do so.
Most of the recent fires in the Washington area occured when the automobiles were parked atop dry fall leaves that accumulated in drifts on the sides of streets.
In one fire on Upton Street in Northwest Washington, burning leaves ignited by a converter spread and set afire two automobiles -- a 1977 Cadillac with the hot converter and a 1978 Chrysler parked nearby, according to Gerald Eckholm, a fire official with the District of Columbia.
Converters can reach an internal temperature of as much as 2,500 degrees Fahrenheit when the car is misfiring, Eckholm said. Normal surface temperatures average 1,000 degrees, he said.
Manufacturers, however, said the maximum surface heat normally isn't more than 550 degrees.
Industry officials contend that the fire risks for cars equipped with converters are no greater than for cars without converters so long as they are tuned up properly.
"The exhaust system on any car is capable of starting a fire and has been for years," said Frank Faraone, a spokesman for General Motors.
Faraone said the company is investigating the reports that three Hartford police cruisers, all 1976 Pontiac Lemans Models, caught fire because of hot converters. GM hasn't had any other reports of problems with converters installed on those models, he said.
The GM spokesman said a 1979 car with a properly functioning converter releases 90 percent less hydrocarbon, 83 percent less carbon monoxide and 51 percent less nitrogen oxide than an early 1960s-model car.
But the chemical process that reduces pollutants is also responsible for the heat. Eckholm of the D.C. fire department said the heat can rise as high as 1,600 degrees inside the converter and 1,000 degrees outside during normal automobile operation.
He also said that studies by the University of Missouri found that converter internal temperatures can soar as high as 2,500 degrees if an engine is in poor operating condition.
There are no precise records of fires produced by the converters. Bill Overby, an official at the U.S. Fire Administration, said federal records indicate that hundreds of fires are caused by overheated exhaust systems, many of them because of converter problems.