The hole in a pen cap
Most ballpoint caps have a small hole through the top. Why would you drill a hole in something meant to keep ink in?
Category: Desk & tools
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Feature. It lets you breathe if a child swallows the cap.
An international safety standard for pen caps asks for a minimum airflow through a cap, so that if one is inhaled it does not completely block the windpipe. The hole is how cap makers meet it.
The myth: You may be told the hole stops ink drying out or equalises pressure. The safety standard is the documented reason.
Source: ISO 11540: Writing instruments, caps, safety against inhalation, ISO.