An increasing number of defective airbags has lead to a record number of recalls so far in 2013, meaning those important safety devices hidden in your dashboard may not work when you need them most.

Over the first 9 1/2 months of 2013, automakers have recalled more than 6 million cars because of possible hazards related to airbag malfunctions, according to National Highway Traffic Safety Administration records.

These defective airbags have injured motorists and, in at least one case, killed a driver. Airbags have, at times, failed to deploy in serious car accidents, deployed on unsuspecting drivers who weren't involved in an accident, and showered vehicle occupants with metal shrapnel when they exploded.

Car makers have conducted 29 separate airbag recalls through mid-October, which is a record for a single year. The previous record of 23 was set just last year. "It's not going to get smaller as time goes forward either," Karl Brauer, senior director of insights at Kelley Blue Book, said.

The most recent recall came Thursday, when Toyota announced it was recalling 803,000 cars in the U.S. because of an electrical short circuit that prevented some airbags from deploying in a car accident. Two "minor" injuries were associated with the recall, according to the company.

Airbags are getting more and more complex, making them vulnerable to problems. But there are other factors leading to the increase in problems: Cars contain more airbags than ever before, making the systems that control the bags increasingly complex. Auto manufacturers are buying airbags from one supplier and using those devices on a variety of car models, so when there is a problem with one car, a larger number of vehicles need to be recalled to fix the issue. And Americans are keeping their cars for longer stretches of time, and aging cars may be more susceptible to problems.

All these factors are melding together to create the potential for problems. Brauer's right. The problem isn't dissipating; it's growing quickly.

Reasons behind the recalls

In car commercials and in movies, airbags are often portrayed as gentle cushions that catch occupants, who then emerge unscratched from accidents. In reality, airbag deployments require violent forces that are unleashed in a matter of milliseconds.

If airbags underperform, injuries or death can occur. If airbags overperform, they risk being the cause of injury or death instead of an accident. The systems that control them must sit dormant for years, and instantly work the one time they're called upon.

Airbags are more complex these days. In 2008 manufacturers begin using Certified as Advanced and Compliant (CAC) airbags. These airbags contain sensors that detect the severity of a crash and inflate accordingly. They also monitor occupant seat positions and measure weight, so they can better protect undersized occupants.

"There are more demands being put on modern airbags," Brauer said. "So it's logical to assume there's more pressure for them to perform under more demands, and that could lead to more recalls."

Curiously, these CAC airbags may be the most advanced, but that doesn't necessarily meant they're safer than their predecessors. A study released earlier this summer by the Insurance Institute for Highway Safety found belted drivers actually had a 2 percent higher death rate in cars equipped with CAC airbags than belted drivers driving in cars with the previous-generation airbags.

Another rising number

Today's cars contain more airbags than ever.

Once, vehicles offered driver-side airbags as standard equipment and a passenger-side airbag was considered a luxury. Both are now mandatory, and more and more, automakers are offering more airbags in efforts to woo safety-conscious customers.

Many offer side-torso airbags and side-curtain airbags, knee airbags for front passengers and rear airbags for passengers in the back. Some offer seat-belt airbags to help minimize the strain of a strap in an accident. This year, Buick pioneered the Front Center Airbag, which helps prevent front occupants from slamming into each other. Volvo has introduced an airbag outside the car for pedestrians.

In 2014, Chrysler and General Motors are both offering 10 airbags as standard equipment on several models, including the Chevy Cruze, Chevy Sonic, Jeep Grand Cherokee and Dodge Dart.

"You have more airbags per car and they're more complicated than they used to be, and you've got seat sensors and occupant sensors and, of course, the pretensioners and seat belts added, all going to a control unit that has many more inputs than it used to have," said Douglas Campbell, president of the Automotive Safety Council, a trade group for manufacturers and suppliers.

Changes in the supply industry

Automakers are buying more of their parts from a single supplier and spreading them far across their lineups, sometimes even across the globe.

They've achieved significant cost savings –- which can be passed along to consumers -– by buying in bulk. The downside to this trend has been that one small problem in the supply chain can ripple across multiple product lines and multiple companies.

In that sense, Campbell doesn't see a concerning trend in the number of recalls as much as he sees isolated problems that affect multiple manufacturers, which shows up in NHTSA's reporting process as more recalls.

"Certainly, there are more than you'd like to see," he said, "but there are tens of millions of airbags being made around the world. ... Companies that make them are really good at it, and you'd be amazed at the double and triple checks they use."

Case in point: Takata, a global supplier of airbags, notified NHTSA in April of a problem with ruptured airbag housings that stemmed from a manufacturing defect. That one issue sparked recalls from Honda, Nissan, Toyota, Mazda and BMW, which recalled 20 different car models across their five lineups that had Takata products installed. Takata products have been involved in 10 of the 29 recalls so far this year. Another supplier, TRW, has been involved in six recalls.

"It is a consequence of a global platform and something a lot of manufacturers are going to run into," Mike Accavitti, senior vice president of operations for Honda, said.

Using one part across multiple products may be one reason why the number of small recalls has actually declined, but the number of larger ones has doubled year over year. Last year, 11 of the 23 recalls, approximately 48 percent, were ones in which fewer than 1,000 vehicles were involved. Only 6 of the 23 recalled more than 100,000 cars. In contrast, less than a quarter of 2013 recalls, 7 of 29, have involved 1,000 vehicles or less, while 13 of the 29 have been for more than 100,000 vehicles.

As much as any other factor, Brauer said he thought he evolution of the supplier base had been the biggest factor in the rising number of recalls.

"Overall, I think the smart parts have been figured out," he said. "They've evolved to that point, and now we're getting this next element of 'How do we deal with the ongoing care of the airbags as part of the process?'"

Pete Bigelow is an associate editor at AOL Autos. He can be reached via email at peter.bigelow@teamaol.com and followed on Twitter @PeterCBigelow.