As we all know, small children love to just put everything in their mouths. For this reason along with older children, or even adults, chew on pen caps. If swallowed accidentally, these caps will allow air to pass through.
Here is what BIC states on their website:
“Why is there a hole in some writing instrument’s cap? (Continued Below)
In addition to help prevent the pen from leaking, all our BIC® caps comply with international safety standards that attempt to minimize the risk of children accidentally inhaling pen caps. Some of these vented caps, like that used for the BIC® Cristal®, has a little hole in the top to comply with the existing safety standards.”