Transcript for Danger in the Backyard: Propane Grill Explosion
You may have heard about our friend and colleague, espn anchor hannah storm, cooking dinner on an ordinary grill, an ordinary night. There was a daung roungerous explosion. She was burned. And because of this, we decided to test the combination of cool weather and give you a warning for every backyard. Here's abc's lisa stark. A great beginning to what should be a spectacular parade. Reporter: It's nearly impossible to tell that our colleague hannah storm is recovering from serious burns. Less than a month ago, her outdoor propane grill exploded. I remember, I yelled inside to my 15-year-old daughter who was in the kitchen, "mommy's on fire, you have to call 911." Reporter: The flames burned her face, neck, chest and hand. Hannah had lit the grill, but when she went to check on it ten minutes later, the flame had blown out. She went to light it again, not realizing that, even though the top had been open, an invisible cloud of propane had formed. I relit the flame and it was a wall of fire, a huge explosion. Reporter: You can see from videos on youtube just how dangerous propane grills can be if not used carefully. Something grill makers warn about. We put it to the test. Watch what happens if you light the grill with the top closed. The gas builds up. And today, james novak of the st. Paul, minnesota, fire department, shows us what happens if the grill goes out. The propane keeps flowing. You go to relight the grill. Watch again, as those doors blow open. Here's what's happening. If the flame goes out, the gas can begin to fill up the grill, especially if the tank is enclosed. And because propane is heavier than air, it is slow to dissipate, even more so in cold weather. Pooling around the tank and grill. So, when you go to relight, this could happen to you. If your grill goes out and you need to relight it, how long should you wait? Most manufacturers instructions will say a minimum of five minutes. Reporter: So, again, if your flame blows out, open the grill, off the valve, wait at least five minutes and trust your nose. Oh, I do smell that. Propane has an added odor to warn you, though hannah says she didn't smell anything. She's just thankful now to be on the mend. Lisa stark, abc news, washington.
This transcript has been automatically generated and may not be 100% accurate.