This can cause a fire if an ignition source is present.

如果存在火源，这会导致起火。

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The LEL of a gas is the minimum concentration of that gas in air at which an ignition source will cause an explosion.

气体的LEL是指用火源使空气中的该气体爆炸的最低气体浓度。

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Since almost all textile materials will burn when exposed to an ignition source, it is necessary to describe or define how these materials burn.

由于几乎所有的纺织材料在遇到火源时都会燃烧，因此有必要对这些材料的燃烧情况进行定义和描述。

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As part of their investigation, Japanese and U.S. experts want to determine if an internal battery failure, or defective lithium-ion cell, was the ignition source in either of the two incidents.

WSJ: All Boeing Dreamliners Are Grounded