What circumstances should safety helmets be replaced?

Safety helmets should be replaced if they have been subjected to a significant impact, even if no visible damage is apparent. They should also be replaced if there are cracks, dents, or any signs of wear and tear that compromise their integrity. Additionally, helmets should be replaced after a certain period, typically recommended by the manufacturer, due to potential degradation of materials over time. Regular inspections and adherence to safety guidelines are essential for ensuring ongoing protection.