Taking a break is mandatory. After 5,5 hours of work, you are officially entitled to a break. These 5,5 hours of work is actually the maximum number of hours that you are allowed to work without a break, because otherwise you will lose your sharpness. If you work longer than 5,5 hours, you are entitled to a minimum of 30 minutes break. If you work longer than 10 hours, you are entitled to a 45-minute break. Deviations from this scheme may be made in a collective labor agreement.
In exceptional situations you may work without taking a break. This is the case when you work alone and do not have direct contact with colleagues (who perform similar work).
If, due to the nature of the work, you do not have the opportunity to take a break, this must be laid down in a collective scheme such as your collective labor agreement, or internal company regulations. How many hours you are allowed to work without a break can also be stated in your collective labor agreement or internal company regulations. Different rules apply within some sectors.