However, it can still burn if a large ignition source is present.

If it found an ignition source, the consequences could be worse.

But then, as now, nobody could find an ignition source.

They drew up a list of five possible ignition sources.

One of the products is hydrogen gas, so avoid ignition sources.

"This is an operation in an area where one wouldn't expect a spark or an ignition source," he said.

The ignition source was a folded rim on the inside of the gun.

More than one red hot spark is often necessary in order to have an effective ignition source.

Steel media may spark, becoming an ignition source for these products.

At the time, safety board officials said they had ruled out those pumps as possible ignition sources.