The May 5 death of a St. Petersburg man whose Smoke-e Mountain vape pen exploded, firing pieces of the device into his brain and setting his house on fire, presents an urgent question about the devices' potential to kill or maim.

Tallmadge D'Elia, 38, is the first recorded U.S. fatality linked to an e-cigarette.

The devices came on the market about 10 years ago, marketed as a safer alternative to smoking cigarettes. Figures vary, but an estimated 4 million to 8 million people in the United States now vape. The battery-powered, rechargeable devices work by heating, but not burning, a liquid containing nicotine and sometimes flavoring to a level where it turns to vapor.

What happened to D'Elia is a rarity, said Larry McKenna, a fire protection engineer for the U.S. Fire Administration who looked at 195 vape device explosions between 2009 and 2016 for a comprehensive report released last year.

AUTOPSY: Vape pen explosion fatally wounded St. Petersburg man.

He said he's only aware of one other fatality, which occurred in the United Kingdom when a vape pen caused an explosion inside the oxygen tent where a man was using it.

Though uncommon, McKenna said vape pen explosions can cause horrific injuries. He looked at cases where people lost teeth, cheeks or parts of their jaw. Frequently the cases involved devices that ignited in pockets causing extensive burns to the thigh and groin. He expects the number of cases to rise along with vaping's popularity.

The Food and Drug Administration's Center for Tobacco Products said it had identified 274 incidents of e-cigarettes overheating, causing fires or exploding between 2009 and 2017, though spokesman Michael Felberbaum said the incidents are under-reported, and they're currently soliciting such reports at www.safetyreporting.hhs.gov.

In August 2017, a Nevada city council meeting was interrupted when a woman's purse caught fire in a viral moment immortalized on YouTube. Another video shows a purse exploding in a department store.

The FDA requires the same nicotine addictiveness warning on vaping products as it does on loose tobacco, but there is no required safety warning when it comes to overheating and explosions.

"It's very safe overall when you consider that millions of people use these devices," said Greg Conley, president of the American Vaping Association, which advocates for vapor products. "The few issues you see are when people use mech mods, unregulated devices that don't have safety features. And in this tragic case, it appears that's the type of device that was being used."

"Mech mods," or mechanical mods, are the vape-industry term for vape pens that users — generally a smaller group of advanced hobbyists — prefer for larger vapor clouds and a more customized experience. That can include aftermarket parts and batteries to create different heat settings.

Mech mods are the types of devices that Smoke-e Mountain and those who sell parts for Smoke-e Mountain vape pens specialize in, Conley said. Mech mods generally don't have safety features such as limiters that automatically shut down the device when the battery pulls too much current, on-off switches that prevent devices from inadvertently turning on in pockets or batteries that can't come loose.

Vaporsource.com, which sells Smoke-e Mountain mods, notes in all caps that the devices are for "advanced users only," and could present a severe hazard if not tested with an ohmmeter.

McKenna said that in the cases he studied, mech mods were responsible for some incidents, but what worries him most is that all vaping devices run on lithium-ion batteries, which contain flammable electrolyte liquid, unlike many other consumer batteries.

"It's not as flammable as gasoline, but make no mistake it is flammable," McKenna said. "If anything causes a short circuit in that battery, it explodes and ignites."

And unlike lithium-ion batteries used in other products like laptops, power tools and hoverboards, the batteries aren't encased in plastic.

"When it ignites, it rockets out because vape devices are a cylinder that's open on one end," he said. He compared the force to a bullet, or "flaming rocket" in the report.

The batteries are sensitive to overheating, short circuiting due to damage or moisture and improper charging.

McKenna said the most important safety advice involving vaping has to do with battery charging. In many cases he looked at the devices caught fire while plugged in.

"Make sure you use the proper charger or USB port. Not all USBs produce the same current, if you have a charger designed to work with one amp and plug it into a three amp you can have a rather unpleasant side effect," he said. "The other thing that has happened with some regularity is spare batteries in pockets reacting to metal. If you drop a bare lithium ion battery in a pocket with keys or change, your pants can catch on fire."

Buying a device from a reputable manufacturer helps. Popular devices such as those by Juul, eVIC and Blu, which Conley says may control as much as 60 percent of the market, have the key safety features.

St. Pete Fire Rescue said the incident with D'Elia was the first "fire of significance" caused in the area by a vape device. A spokeswoman for BayCare Health System said emergency rooms across their 15 Tampa Bay hospitals have yet to treat a vaping injury.

Still, some doctors warn that vaping injuries could rise. Joshua Williams, a pediatrician at Denver Health Medical Center and assistant professor at the University of Colorado, was part of a team that published the first paper on vape injuries in children after treating a 17-year-old who lost a large piece of his thumb to an exploding vape pen. The paper also noted that due to the alkaline chemicals released, anyone who suffers such an explosion could actually make the burn worse by washing it with water and should instead seek immediate treatment.

"It's incredibly unfortunate, but no, it's not surprising that someone would eventually die like this considering the injuries we've seen," he said.

James Gaensbauer, assistant professor of pediatrics at Denver Health Medical Center who also worked on that paper and treated that patient, said the teen was using the device properly.

"They can spontaneously explode, it can happen," Gaensbauer said. "Sometimes adolescents aren't necessarily attuned to what's going to affect their long-term health, so the possibility of severe injury could be another thing parents should caution them about."

Contact Christopher Spata at cspata@tampabay.com. Follow @SpataTimes.