Apple's new iPad goes on sale this Friday, the latest version of a wildly popular product from an iconic company. In the past couple of months, though, Apple has come under criticism for working conditions in Chinese factories that help build iPads.
A New York Times investigation focused on an explosion at an Apple supplier factory last May. In December, another explosion struck a different Apple supplier factory in Shanghai.
Last week, NPR met with 25 workers injured in the Shanghai blast and they criticized safety at the plant and said Apple had inspected it just hours before the explosion.
He Wenwen says he was calibrating his machine, which polished aluminum backings for the iPad 2, when the explosion hit.
"I saw a fireball coming towards me," says He, lit by a lone fluorescent tube in a Shanghai hospital, where he and co-workers seek continued treatment for their injuries.
"I lost consciousness for a few seconds," he says. "Later, when I opened my eyes, I saw dense smoke and fire everywhere. I felt scared, really scared. I could hear people crying and screaming."
Fifty-nine workers were injured in the explosion, according to Apple.
The fireball singed He's face, leaving the upper half badly burned. More than two months later, the 24-year-old still looks like he's wearing a bright, red mask. He worries his disfigurement will make it harder to find a wife.
"For a young man like me, still single . . . this injury has a real impact," he says. "I often quarrel with my girlfriend about it."
Apple blamed the explosion on a build-up of dust, fueled by aluminum particles from the polishing process. Pegatron, the factory's owner, said the explosion started in equipment that collects the particles.
Dust explosions are not uncommon — even in the United States.
The U.S. Occupational Safety and Health Administration says an average of 15 dust explosions a year occurred from 1980 through 2010. Bob Zalosh, who has studied dust explosions since 1975, says the most common material involved is wood, followed by coal, aluminum and grain.
Zalosh, who has a doctorate in mechanical engineering, says a spark can ignite a dust cloud, inside equipment or floating in the air.
"If it's really fine aluminum, we know that's capable of creating quite a nasty explosion or fireball, because it has a very high flame temperature," Zalosh says.
He Wenwen, the worker in the Shanghai iPad plant, says each polishing machine had an exhaust pipe, but dust was still a constant problem at the factory.
"We wore face masks, very thick masks," He says. "But when we took them off, our nostrils were full of dust. The air in the factory looked a bit like fog."
He says there was a system for vacuuming away the dust, but it wasn't that effective and the factory windows were sealed shut.
Seven months earlier, a dust explosion ripped through another iPad factory in the Chinese city of Chengdu. That factory is owned by a different Apple supplier, the huge Taiwanese company Foxconn. The blast killed four workers but got little coverage in China's state-run press.
Zhang Qing, who worked in the Shanghai factory, said employees were never told about the explosion in Chengdu or that dust was actually combustible.
"When we first got here, they never told us this could explode," Zhang says.
Zhang and his fellow workers in Shanghai earn a base wage of about $200 a month and up to $450 with overtime. The day of the Shanghai blast, managers told them to clean up dust because Apple inspectors were visiting.
Liu Hengchao, another injured plant worker, recalls watching the inspectors.
"They wore white gloves to check if there was dust," says Liu, an articulate 29-year-old from central China's Henan province. "There certainly has to be dust."
Liu says management told workers not to talk to the Apple inspectors, who spent 10 minutes in the area and then left. Liu says if he'd been allowed to speak, he would have told them this: "They could improve the environment somewhat, because the environment is too terrible."
Apple and Pegatron declined requests for interviews. In a recent report, Apple said it investigated the May explosion and had sought ways to avoid future ones. Apple did not explain why those efforts failed to prevent the Shanghai explosion seven months later.
Apple also says it has established new requirements for handling combustible dust, including regularly testing the air flow in ventilation systems.
"Apple takes working conditions very seriously and we have for a very long time," Tim Cook, Apple's CEO, said at an event last month in response to public criticism.
Apple has contracted with an industry-supported monitoring group to interview tens of thousands of workers at Apple suppliers.
"The Fair Labor Association began a major audit of our final assembly vendors at our request," Cook said. "The audit they are conducting is probably the most detailed factory audit in the history of mass manufacturing."
When I met the Shanghai factory workers at the beginning of last week, all 25 said no one from Apple had ever contacted them about the explosion.
Later — after NPR contacted Apple — other workers said they finally started receiving calls from the company, checking on their injuries and making sure they'd received compensation, which came to about $800 each.
NPR's Steve Henn contributed reporting from Silicon Valley.