Why do pen caps have a hole in the top?

The hole is mainly a safety feature. If someone accidentally inhales a pen cap, the hole lets some air pass, so the cap does not completely block the airway. Bic states that this is requested by the international safety standard ISO 11540, except where a cap is considered too large to be a choking hazard. The claim that the hole prevents choking is true, according to Snopes. [1] [2]

The idea appears to have started in the United Kingdom, which adopted a safety standard, BS 7272, in 1990. Snopes reports that nine children in the UK died from choking on pen caps between 1970 and 1984, and that a 2004 report said no such deaths had occurred since the UK adopted the international standard. A Bic spokeswoman said the company began perforating the caps of its Bic Cristal in that same year and decided to apply the British norm worldwide. [1]

The international version, ISO 11540, was first implemented in 1993 and revised in 2014 and 2021. It covers requirements to reduce the risk of asphyxiation from caps of writing and marking instruments likely to be used by children up to age 14. Reader's Digest gives 1991 as the year companies including Bic began adding the hole, which differs slightly from the 1990 date in Snopes. [1] [3]

A hole is not the only option. According to Bic, a cap might have a single hole, several holes at the top (often the case for markers), or be large enough, more than 16 millimeters in diameter, to be considered too big to swallow. The Design Museum notes that the hole in the top of Bic caps is there to comply with health and safety regulations and reduces the risk of suffocation if the cap is swallowed. Snopes says most ballpoint manufacturers now comply with ISO 11540. [1] [4]

Several popular articles say the hole also equalizes air pressure so the pen does not leak, or that it keeps ink from drying out. Reader's Digest says the ventilation stabilizes air pressure and keeps ink from drying, and Bic's FAQ, quoted by Snopes, says vented caps let more air circulate around the pen point. Business Insider and ScienceAlert also mention pressure equalization. However, the Design Museum attributes pressure equalization to a separate small hole in the barrel of the pen, and Bic's own statement of the reason for the cap hole focuses on the airway. So the airflow benefit is claimed by some sources, but the safety purpose is the one tied to the standard. [3] [1] [5] [6] [4]