Cap safety for writing pens 

There are separate standards/requirements for pen caps and end plugs contained in writing and marking instruments designed for children up to 14 years of age in order to reduce the risk of asphyxiation. 
 
These are detailed below. Expensive and professional pens and refills are excluded. 
Standard: 
Application: 
BS7272 Part 1 
British Standard for detachable pen caps 
 
Applies to the pen cap size and airflow 
BS7272 Part 2 
British Standard for pen end closures and plugs 
 
Applies to size; security, including inaccessibility and minimal protrusion; air flow; and additional safeguards