ISO 14121-1:2007(E)

The structure of safety standards in the field of machinery is as follows.
a) Type-A standards (basic standards) give basic concepts, principles for design, and general aspects that can be applied to machinery.
b) Type-B standards (generic safety standards) deal with one or more safety aspect(s) or one or more
type(s) of safeguards that can be used across a wide range of machinery:
⎯ type-B1 standards on particular safety aspects (e.g. safety distances, surface temperature, noise);
⎯ type-B2 standards on safeguards (e.g. two-hands controls, interlocking devices, pressure sensitive devices, guards).
c) Type-C standards (machine safety standards) deal with detailed safety requirements for a particular machine or group of machines.
This part of ISO 14121 is a type-A standard as stated in ISO 12100-1.
When provisions of a type-C standard are different from those which are stated in type-A or type-B standards,
the provisions of the type-C standard take precedence over the provisions of the other standards for machines
that have been designed and built according to the provisions of the type-C standard.
The purpose of this type-A standard is to describe principles for a consistent systematic procedure for risk assessment as stated in ISO 12100-1:2003, Clause 5.