KNOXVILLE, Tenn. (WVLT) -- Two elderly brothers are in the critical care unit at UT Medical Center because of what firefighters call a big mistake.

George and John Herndon-- identical twin brothers-- were burned when they started a fire and it "flashed," or ignited.

It was their neighbors who came to their rescue.

"They're true friends of mine," Greg Chambers said, "and I just wanted to get them out."

On Monday morning, Chambers' hands were still covered in soot; He lives above the elderly Herndon brothers at Knob Hill apartments and last night, he was one of their neighbors to come to their rescue.

"Smoke was so thick, coming off the windows and front door that fire was actually crawling the walls when I went in," Chambers said.

Around 11:30 p.m. Sunday, the apartment complex's power went out and fire investigators say the Herndons caused a flash fire when they used lamp oil on the stove as a source of light.

They were burned on their arms and upper bodies.

"Luckily, the smoke wasn't bad enough for me to crawl in there and pull one of them out," Chambers continued.

Firefighters say flash fires are dangerous and can be avoided.
Often, it's the misuse of a product that spark flames.

Lamp oil should be used with a wick-- not on a stove.

To demonstrate what may have caused the Knob Hill fire, Knoxville firefighters stood by in full turnout gear with a fire extinguisher.

Watching how quickly the small flame grows, firefighters pointed out how quickly something like that can get out of hand.

Even putting it out can be a problem, especially if the lamp oil had splashed onto the carpet or clothing.

And, if the brothers had thrown water on it, it would have acted like a grease fire and spread.

Instead, you have to smother the flames.

For more tips on fire safety, click here.