What is the tiny hole in a pen cap for?
Quick Answer
It is a safety feature. If a child swallows the cap and it gets stuck in the airway, the hole lets some air pass through. An international standard for pen caps calls for it.
The Full Story
Many people assume the hole in a pen cap stops the ink drying out or evens out the pressure, but its main purpose is safety. Pen caps are small enough for children to put in their mouths, and some are inhaled by accident. The international safety standard ISO 11540, which covers caps for writing and marking instruments, asks for caps to be designed so that a minimum amount of air can still flow if one is swallowed and blocks the airway. A hole in the top is the simplest way to meet it, and some makers also use ridged or open-ended caps. The hole does not make swallowing a cap harmless, and a choking child still needs urgent help, but it can buy precious time.
Key Facts
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"The tiny hole in your pen cap is there to save a life"
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