Once every couple of weeks, a sharp explosion rattles the walls of Bill Irwin's office overseeing the junk car shredder at a Baltimore scrap yard.
Another air bag has been triggered inside the United Iron & Metal Co. shredding machine that every day grinds 600 cars into scrap metal. The noise scares Mr. Irwin.
But scarier still are the air bags that don't explode. If the shredder tears up an air bag without setting it off, the scrap and air could become contaminated with the toxic chemical hidden deep inside the steering column. The chemical, sodium azide, normally explodes harmlessly to inflate the bag during a crash.
Air bags, the life-saving devices that new-car buyers are increasingly demanding, are turning into dangers for the the final buyers of used cars -- scrap yards.
Car recyclers warn that unless carmakers switch to a safe-to-recycle air bag, the devices may finish off the automobile recycling industry and turn the 10 million cars junked every year into a monumental trash disposal problem.
Air bags, credited by the National Highway Transportation Safety Administration with saving the lives of 115 drivers so far, haven't been blamed for any injuries or illnesses at scrap yards yet, according to Dan Rouse, an air bag expert with the Automotive Dismantlers and Recyclers Association.
Scrappers say it may just be a matter of time, though.
There is more than an ounce of the explosive, poisonous sodium azide in each air bag firing device, according to air bag manufacturer Morton International Inc.
And the Occupational Safety and Health Administration warns that it is lethal to swallow as little as seven drops. Breathing or touching the chemical can also be fatal, but at higher levels, the safety agency says.
"Many lives can be saved by air bags. But they can be lost in scrap recycling," says David Serls, president of a scrap yard in York, Pa., and head of the Institute of Scrap Recycling Industries.
"Lives are just as precious in a scrap yard as they are on a highway," he said.
Drivers aren't endangered by the chemical because the sodium azide is encased in an aluminum or steel canister. If set off by a crash, sodium azide burns into harmless nitrogen that is cooled and filtered and then goes into the cushion that protects the driver's head.
But recyclers are at risk if they disconnect the air bags improperly, or come into contact with the toxin during the shredding process.
Because air bags are comparatively recent innovations, junkyards have only recently begun to handle discarded cars with unfired devices still in the steering wheel.
But about 40 percent of the 10 million cars to be made in the United States this year will have driver's-side air bags, according to TRW Inc., one of the biggest U.S. air bag manufacturers. By the end of the decade, most cars will be equipped with at least one air bag.
As those cars age, a larger share of the 10 million cars junked each year will contain canisters of sodium azide, Mr. Serls figures.
"The economics of the recycling industry are getting worse," Mr. Serls said, explaining that recyclers already must remove gas tanks, lead batteries, tires, catalytic converters and plastic parts before turning cars into scrap steel that sells for about $50 a ton.
Though they could solve the problem by setting off or removing the air bags before they send the cars through the shredder, Mr. Serls said that adding another costly and dangerous task to the recyclers' list "could render autos unrecyclable. That's 60 million tons a year that would have to go to landfills."
It may already be happening.
Mr. Irwin said that United Iron & Metal is considering passing the word to its Baltimore-area suppliers that it won't buy junkers with unexploded air bags any more.
Some companies are hoping to capitalize on the scrappers' concerns by making a non-toxic air bag. OEA Inc., an Aurora, Colo.-based company that is one of the prime suppliers of air bag parts, has developed an air bag that uses a pressurized bottle of non-toxic argon gas to inflate the bag, said Brian Hamilton, who manages the project for OEA. The company has joined with Chicago-based Morton International to develop the alternative and expects some major automakers to start installing their non-toxic air bags in 1994, Mr. Hamilton said.
General Motors Corp., entering its third year of providing sodium-azide air bags, is warning junkyards not to remove unfired air bags for sale as used parts, said Jack Drinan, a GM spokesman.
Taking out unfired air bags and installing them improperly is dangerous, he warns. "Every model's steering wheel cover design is different. And the difference is enough to maim somebody." If an air bag fires into the wrong cover "it could blow somebody's eyes out," he said.
Mr. Hoffman, whose A & B Auto Recyclers Inc. buys and dismantles about 300 cars a year, said the dangers and costs of disposing of air bags safely may finish off the troubled car recycling industry.
"You can go through most neighborhoods and find piles of cars hidden in the bushes. Nobody will come and get them any more," he said. "This is a dying industry."