In response to concern over the risk of injury from caps missiling from carbonated drinks bottles during opening, a multi-disciplinary study was undertaken to identify the technical and ergonomic factors involved in this potential hazard. The specific conditions causing missiling were identified and an ergonomics approach was used to assess the likelihood of this combination of mainly behavioural factors. It was found that under ‘normal' conditions, caps are unlikely to missile, suggesting that the risk from this product is low. Strength data collected in this study suggested that caps were applied with too great a torque for some users – particularly children and the elderly – to be able to open carbonated drinks bottles easily. User trials and a field study of naturalistic behaviour suggested that ‘tools' are used to open bottles and some users may turn the caps the wrong way during opening, which together with an increase in temperature were the main factors likely to cause missiling.