Two iPhones exploded: Will your iPhone combust?

Earlier this week, an iPhone 4 battery combusted on an Australian flight. It all started when a passenger's cell phone emitted a significant amount of smoke. Fortunately, a flight attendant extinguished it in time.

A second iPhone 4 battery combusted just inches away from Ayla Mota's face. The Brazilian cell phone owner was charging her phone -- then it combusted and began to emit smoke.

These stories raise questions about the safety of the iPhone batteries. What is to blame? Is it the battery quality or could it be a counterfeit phone?

I asked battery expert Jay Whitacre at Carnegie Mellon University about the risks:

By my count there have been something like 100 million iPhones made.  If there is 1 failure per every 1 million phones sold -- these are some solid odds.

It is not clear that you can engineer this battery any better. Li-ion batteries are full of combustable organic electrolyte solvent and if anything goes wrong, the potential is there for a blow out.

So we will likely continue to see this rate of failure... If failure rate is higher than 1 in 1M, then that's a bigger deal.