Every hard hat has the date of manufacture imprinted on the inside rim of the hat itself, it is usually in the form of a circle similar to a clock.
To read the date of manufacture, the arrow points to the month and the number in the center is the year.
It is recommended that hard hats be replaced no later than every five years due to natural degradation over time. In some cases and related work environment conditions, hard hats will need to be replaced more frequently.
All hard hats are classified according to the specific impact, and electrical performance requirements they are designed to meet. This classification is also commonly referred to as the ANSI Z89.1 standard.