Billions of people use smartphones every day without worry, but sometimes, they turn deadly. The question is why. While the circumstances are different in each case—there might be a bad charger, faulty wiring, or poor judgment on the part of the user—the risks are real.

Here's a look at four ways smartphone electrocution can occur and how to make sure it doesn't happen to you.

Don't Charge and Use Your Cellphone While in Water

In December 2016, a 32-year-old British man was found dead in the bathtub. The cause was a charging smartphone. He was resting a charging iPhone on his chest when the device made contact with the water. His injuries were severe, including burns on his chest, arms, and hand.

While a cellphone looks like a harmless device, it can be as deadly as a hairdryer when it is plugged into a charger. Consider that it only takes seven milliamps (mA) applied for three seconds to kill a person. Add water to the mix, and you have a risky situation.

Water lowers your body's natural resistance to electricity, which means you're more likely to die if you contact electricity in the bath or shower. Saltwater lowers your resistance even more.

To prevent cellphone electrocution:

• Never charge your smartphone in the bathroom or near water.
• Don't let extension cords or chargers come in contact with water.
• Never use extension cords or chargers with frayed wires.

Using Your Cellphone While It's Charging

While smartphone batteries carry a low voltage—lithium-ion batteries are about 3.7 volts—attaching them to a charger puts you in a direct line to the high-intensity voltage from the power socket. This can be dangerous under certain conditions, such as when there's a short circuit or power surge.

A case in point: A 24-year-old factory worker in Thailand was found dead in his bedroom in 2019. His cellphone was plugged into the wall while he listened to music on his earbuds. For some unlucky reason, electricity surged into the phone, making contact with his ears. Police believe that a short circuit or a faulty charger was to blame.

To prevent cellphone electrocution:

• Don't use earbuds plugged into a charging cellphone.
• Plug your cellphone charger into a surge-protected power strip when possible.

Using a Counterfeit Cellphone Charger

The cost of replacing smartphone chargers can be enough to make your eyes water. It can be tempting to purchase a knock-off for a fraction of the price, but experts say don't do it.

According to a study from the Chartered Trading Standards Institute in the UK, 98 percent of all fake Apple chargers failed basic safety tests. After several tests, only three of the 400 devices tested had enough isolation to prevent an electric shock. These are scary statistics by any measure.

To prevent cellphone electrocution:

• Only use OEM (original equipment manufacturer) chargers for your smartphone.
• If you suspect a charger is fake, check the manufacturer, model number, and voltage ratings.
• If you doubt a charger's authenticity, throw it out.

Charging Your Cellphone in Bed

In 2017, a girl was electrocuted by her phone charger. The 14-year-old teenager from Vietnam was charging her iPhone 6 in bed when she rolled onto a frayed cable and was electrocuted in her sleep. Tape wrapped around the cable indicates she was likely aware of the frayed cable for some time but failed to replace it before the worst happened.

To avoid smartphone electrocution:

• Never charge your cellphone in bed.
• Replace faulty or frayed charging cables immediately. Don't tape them up as a band-aid measure.
• Don't touch frayed or damaged cables when your charger's plugged in.
• Plug your cellphone charger into a surge-protected power strip when possible.

There's No Need to Panic

If all of this information has you a bit on edge, remember that the odds of cellphone electrocution are minuscule. It requires a weird mix of events to happen, which is probably why it's not common. Still, it's a smart idea to follow common-sense precautions and stay safe.