ISO 11540:2021

Overview

ISO 11540:2021 specifies safety requirements for caps on writing and marking instruments to reduce the risk of asphyxiation, particularly for products that children up to 14 years of age are likely to use. The standard applies to detachable caps and requires either a cap size that is too large to be inhaled or ventilation performance that allows sufficient airflow if a cap becomes lodged in the airway. It excludes instruments designed or intended only for adults (e.g., jewellery pens, expensive fountain pens, professional technical pens) and transit caps for refills.

Key topics and technical requirements

• Conformity options: Caps must meet at least one of two options:
  • Cap size test (4.2) - A cap introduced perpendicular to a 16 mm ring gauge (≥19 mm thickness) must have at least 5 mm of length that does not enter under its own weight; caps meeting this are deemed too large to inhale.
  • Ventilated caps air flow (4.3) - Caps tested per Annex A must permit a minimum air flow of 8 L/min at a maximum pressure drop of 1.33 kPa (measured at room temperature). Caps meeting this are deemed not to present an asphyxiation hazard.
• Airflow test method (Annex A):
  • Cap is fully inserted into elastomeric tubing; airflow and pressure drop measured in both directions.
  • Apparatus includes pulse-free air supply, flow regulator, flowmeter (5–10 L/min accuracy ±0.2 L/min), and pressure gauge (accuracy ±0.01 kPa).
  • Elastomeric tubing internal diameter: 80–85% of the cap’s circumscribing circle; wall thickness 0.75 mm ±0.25 mm; Shore A hardness 55 ±10.
• Design guidance (Annex B):
  • Continuous air passage of at least 6.8 mm along the cap body, extending to within 2 mm of both ends.
  • Cross-sectional vent area may be assessed by the cotton-thread method or CAD. Clips providing ventilation must be securely fixed and extend to within 2 mm of each end.
• Test reporting and identification (4.4 & 5):
  • Test reports must state whether the cap conforms via size or airflow and include tubing size, number of caps tested, bi-directional airflow results, and minimum flow recorded.
  • Products must be legibly identified with manufacturer/supplier name or trademark.

Applications and users

• Product designers and manufacturers of pens, markers and caps - to design caps that comply with child-safety requirements.
• Product safety engineers and compliance officers - for conformity assessment and documentation.
• Test laboratories - to perform the Annex A airflow test and produce compliant test reports.
• Regulators and procurement - for specifying safety requirements for school and children's stationery.

Related standards

• ISO 11540 references ISO 1938-1 (geometrical product specifications - plain limit gauges). Manufacturers should also consider relevant product safety and toy-safety regulations when placing items intended for children on the market.

Keywords: ISO 11540, pen cap safety, ventilated caps, asphyxiation risk, writing and marking instruments, cap airflow test, elastomeric tubing, cap design guidance.