Because the sound of an alarm may be difficult to hear in long underground tunnels, many mining operations use a stench-based alarm that pumps a powerful odor into the air ventilation system to signal emergency evacuation.

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Why Do Our Noses Have Two Nostrils?

When it comes to eyes and ears, pairs make sense. Paired eyes give us stereo vision, which allows us to see objects in depth, and paired ears give us stereo hearing, which allows us to detect the direction a sound is coming from. The reason for paired nostrils, however, is a little less obvious.