OSHA does not specify the service life of a hard hat, and there is no standard expiration time frame for hard hats. Hard hat life span may vary depending on the conditions of each work site. As a general guideline, most hard hat manufacturers recommend replacing hard hats every five years regardless of outside appearance. If you work under extreme conditions, such as exposure to high temperatures, chemicals, or sunlight, hard hats should be replaced after two years of use. In addition, some manufacturers even recommend replacing the suspension in your hard hat every 12 months. It's important to review each work site to ensure that degradation of employees' hard hats is not being accelerated due to work conditions.