Pilz PSS SB FT, Basic license - Manual (Page 13)

1-3 Modular Block System: Burner Management
Categories / requirement classes
EN 954-1 divides safety devices into categories.
All standard function blocks are designed for the highest category
permitted for the safety device to be monitored. If safety devices with lower
categories are to be monitored, input parameters may be assigned
identical inputs (further information can be found in the description for the
relevant standard function block).
In process engineering, safety requirements must conform to DIN V 19250
(Fundamental Safety Aspects to be Considered for Measurement and
Control Equipment).
Requirement classes in accordance with DIN V 19250 may be referred to
the categories as per EN 954-1. The Appendix contains a table showing
the assignment of category and requirement class.