All hard hats must have the following characteristics:
- Impact resistance: They must absorb and resist the shock caused by a blow to the head to reduce injury from falling or moving objects.
- Penetration resistance: They must resist penetration by falling or stationary objects that could puncture the shell.
- A built-in suspension system: This acts as a shock absorber to cushion impacts and keep the shell spaced from the head to reduce force transmitted to the skull.
- Electrical protection: Many hard hats must meet electrical insulation requirements to protect against electrical shocks, depending on the class of hard hat.
- Compliance with standards: Hard hats must meet safety standards such as ANSI Z89.1 in the US or AS/NZS 1801:1998 in Australia, which includes testing for impact, penetration, and electrical resistance.
- Water resistance and fire resistance: Hard hats should resist water and slow burning to provide additional protection in hazardous environments.
These characteristics ensure that hard hats provide effective head protection on construction sites and other hazardous workplaces.