What condition should a helmet be in to ensure safety?

A helmet should not have been previously worn in an accident to ensure safety, as an impact can compromise its protective features, even if no visible damage is evident. Helmets are designed to absorb shock, and once they have undergone significant force during an accident, their integrity may be compromised, making them less effective in protecting the rider in future incidents.

While having no scratches, being from a trusted brand, and fitting snugly are important factors for helmet safety, these do not address the crucial aspect of the helmet's history regarding any prior accidents. A helmet's ability to protect is fundamentally linked to its condition, and a previously compromised helmet cannot be trusted to perform as intended. Thus, ensuring that a helmet has never been involved in an accident is a critical consideration for safety.