Question

some types of head protection: hard hat or safety helmet offers protection against falling objects or impact. protective cap protects against small impacts, but not against falling objects. service life a hard hat has a service life of 5 years, on average. this depends on its material. the service life can also be shortened by: chemicals direct sunlight climate the user manual states the maximum service life. extra features a hard hat often offers the possibility to fit a face visor and/or ear defenders. these can protect you against noise and splashed liquids. note:never use a hard hat that has been deformed by a falling object. 1 when are you required to use a hard hat? in places where you can bump your head. in places where you can get hit by falling objects. on seeing the appropriate mandatory sign. when your employer tells you it is unnecessary.

Explanation:

Hard hats offer protection against falling objects or impact. So, they are required in places where one can get hit by falling objects. Also, in places where bumping the head is possible, hard - hats can provide protection. Mandatory signs indicate when their use is required. An employer indicating it's unnecessary means it's not required then.

Answer:

In places where you can bump your head.
In places where you can get hit by falling objects.
On seeing the appropriate mandatory sign.