Lawyer Sue Yap remembers the day when her shower screen spontaneously shattered in 2008.
"It was about 6.15am, and I was still asleep, when I heard a bang coming from the (ensuite) bathroom of my apartment. I went into my bathroom to have a look, and that's when I realised that my shower screen had shattered," says Yap, 36.
Yap adds that she had only had the tempered glass shower screen installed for about a year then.
"I was very surprised because it seemed to have shattered for no apparent reason. But I'm very thankful that I was still sleeping at the time, so I wasn't hurt. I'm very sure I wasn't told of this risk when I got my shower screen installed.
"After the incident, I did some reading up online but I didn't come across any local cases, although there were similar cases reported overseas. I don't have any family members or friends who have experienced anything like this, so I guess I'm the unlucky one," she says.
Yap has since replaced the shower screen with a plastic one.
"No more glass shower screens for me," she quips.
Yap's case is not an isolated one.
According to National Consumer Complaints Centre (NCCC) legal executive K. Santhosh, the centre received about 10 similar complaints last year alone.
"Almost all were about the tempered glass on their furniture 'inexplicably exploding'. Although there were only 10 complaints, we actually had more than 40 enquiries on this issue," he says.
"We have advised the consumers to either file a complaint with us or go straight to the Consumer Claims Tribunal (under the Domestic Trade, Co-operatives and Consumerism Ministry). I believe many of them went to the tribunal."
Such cases are not limited to Malaysia.
In 2012, ABC News reported that the United States Consumer Product Safety Commission (CPSC) had received more than 60 complaints (in over eight years) from across the US of shower doors shattering for seemingly no reason.
"The sudden explosions can cause serious lacerations and bleeding, according to CPSC incident reports ... with some people reporting that they needed stitches and surgery after being 'covered in glass' or having glass 'embedded' in their skin," the news report said.
Over the years, tempered glass has become increasingly popular in Malaysian homes, due to its strength and versatility, says Ajiya Safety Glass Sdn Bhd executive director Sim Chee Liang.
"In the early 1990s, Malaysia only had one or two tempering furnaces. Today, Malaysia has about 40 tempering furnaces, with about 20 players in the industry, so you can see how much the industry has grown over the last 20 years.
"Tempered glass can be used as shower screens, kitchen backsplash, table tops (furniture), partitions, staircase railing, wardrobe doors ... there are so many uses for it."
Sim says tempered glass is classified as safety glass, and is three to five times stronger than normal glass.
"It is manufactured by heating ordinary float glass to its softening point, at about 700°C, then cooling the glass rapidly by quenching it with a uniform blast of air on both surfaces simultaneously. When broken, it breaks into a multitude of small fragments, which offers some protection against serious injuries.
"However, if it were to break or burst at high speed, it could still be dangerous," he explains.
What could cause tempered glass to shatter?
"Tempered glass can break for a variety of reasons, even though it is stronger than normal glass. It can break from impact, or if the glass edge or surface has been damaged from handling or glazing. If you have a tempered glass table and the edge has chipped, it is no longer considered safe; that chip could eventually cause the whole piece of glass to shatter.
"Structural movements from, say, major renovations going on next door, could also cause the tempered glass to shatter," he says.
As for spontaneous breakages, Sim explains that it could be caused by nickel sulfide inclusions, although such cases are generally rare.
"It's the presence of microscopic impurities of nickel sulfide in raw glass, which unfortunately cannot be complete removed," he says.
Mark Meshulam, a glass specialist in the US, explains nickel sulfide inclusions as "a tiny rock of unmelted material that remains in the glass".
"You can well imagine that a little rock embedded in a slab of glass which is under high tension or compression forces, could weaken the glass and eventually cause breakage. But the story gets worse - nickel sulfide grows an additional 4 per cent of its size over time, especially in the presence of heat. If it is located in the strata in the glass between tension and compression, and it grows ... kaboom!" he says on his website, the Chicago Window Expert.
Sim says heat-soaked tempered glass have a much lower risk of spontaneous breakage.
"A test which will eliminate nickel sulfide inclusion as much as possible, is a heat soak test in accordance to the BS EN 14179 Standard, which is a common test used in Europe. It's basically a stress test, so that if the glass breaks, it breaks in our furnace and not in your home.
"But heat-soaked tempered glass costs about 15 per cent more than normal tempered glass, and delivery might take a few days longer, which is why consumers still sometimes choose normal tempered glass. But if you're using tempered glass for your shower screen, I would highly recommend using a heat-soaked one for safety reasons, " he says.
Sim adds that only about 25 per cent of the industry players offer heat soak tests which adhere to the standard listed above.
Consumers should also be aware that tempered glass is not always suitable for every occasion.
"Some consumers use tempered glass for their canopies or skylights, but that's not suitable at all! Minimally, they should be using laminated glass so that even if it cracks, it will not shatter, and they have plenty of time to replace it.
"Ask to find out what kind of glass you're getting," Sim says, adding that many China-imported tempered glass do not meet international safety standards.
"Consumers need to be more savvy about what they buy. Read up before you make a purchase, so that you can make an informed decision, and you are aware of the risks involved.
"At the same time, perhaps the relevant ministry could look deeper into this issue, as it is a matter of consumers' safety.
"Perhaps there should be requirements in place to ensure that glass used for furniture and in the home should always meet international safety standards. Safety should always be a priority," he says.