Willie Mae Truesdale heard a loud explosion coming from her kitchen. When she went to investigate, she found her glass oven door in pieces all over the floor. “It was shocking and you had to really see it to believe it,” she explained.

“It was like what in the world. Glass shattered, glass was out here on the floor.” To add to the confusion, her oven wasn’t even on at the time. And what’s scarier: Truesdale is far from the only homeowner whose oven exploded.

She tried to bake brownies but they came out soggy in the middle. Her oven was only three months old but she realized its temperature was about 25 degrees off. After quarantine, she called a professional to fix her appliance. But first, she decided to put it on a self-cleaning cycle. Towards the end of it, there was a loud explosion and the inner glass over the door shattered into the oven.

But Michelle Wheat’s oven door explosion left her with glass all over her kitchen. Like Truesdale, Wheat’s three-year-old oven was not on at the time. Fortunately, none of her four young children were injured from the glass. And like Truesdale, her oven came from Frigidaire, Cheryl’s was Bosch, but other brands also have reports of exploding glass doors. In fact, the Consumer Product Safety Commission has received about 450 reports about this occurrence since 2019.

Unfortunately, all three women struggled with the manufacturers after the event. Truesdale’s oven was still under warranty, but Frigidaire’s technician blamed the family for the explosion even though the oven was off. So she had to pay for a new door out of pocket. Luckily, Bosch replaced Cheryl’s oven after NBC reached out to them for comment.

Meanwhile, Wheat’s oven was no longer under warranty and she had to pay the technician $100 only for him to say the glass was broken and they needed to replace it, which cost the family another $314. Frigidaire suggested Wheat buy an extended warranty in case this happened again. “This should not have happened,” said the frustrated mom of six. “That was the point I was trying to make to them.”

“There are two scenarios of why oven glass can break spontaneously,” says Mark Meshulam of Chicago Window Expert. “There’s one family of oven glass that is soda lime glass, which is window glass, and it’s heated and cooled rapidly so that it becomes tempered. That’s one type of glass that is used in oven doors. Another type is borosilicate glass. It is more used in laboratory glassware or the old time Pyrex glass, and that one tolerates heat and cold very well. So, the shift to soda lime glass has brought about an increase in these types of breaks because it’s not as tolerant of the thermal cycles that the glass will go through.”

But it’s also likely the explosions come from a nickel sulfide inclusion, a minuscule flaw in the glass. “It’s only about a tenth of a millimeter in diameter. That little ball has some strange properties.” Meshulam said, adding, “over time it’s fighting to get out. And sometimes the high heat event like oven cleaning event can bring about that finally that spontaneous failure that was in there.”

Nevertheless, Meshulam reassures people that ovens’ self-cleaning feature is safe. “Most people will survive their whole lives using the self-cleaning feature and not really encounter this problem,” he said. He also believes that microscopic chips and flaws are the cause of ovens exploding when they aren’t on. But what’s especially frightening about this possibility is that the door can shatter a long while after the initial damage occurs.

Sometimes these tiny points of damage can happen during production, shipping, or installation. These situations are beyond homeowners’ control but there are ways to avoid damage at home. For instance, a few common habits can put microscopic scratches or chips onto the glass. These include aggressive cleaning techniques and too much physical impact.