Pen caps now have requirements that they have holes in them to facilitate air passage in case somebody chokes on the cap.


Here are a few links about pen caps

Info from about a bid to manufacture pen caps -

People actually choke on parts of pens -;jsessionid=G2jKg74ChcLJxTnHlr28nPhlyp2yKqHPZQ38XwgvJpqFHC0vthnw!-447275640!-949856144!8091!-1


Medical info on choking -