Siemens SIMATIC S7-1500 System Manual page 503

Use over 2 000 m above sea level and extended temperature range
C.3 Restrictions
Effects on availability
The higher cosmic radiation present during operation at altitudes above 2 000 m will also
start to have an effect on the failure rate of electronic components (the so-called soft error
rate). In rare cases, this may result in particular in a transition of the HF-CPU into the safe
state. However, the functional safety of the HF-CPU is fully retained.
Note
Information on the components of the S7-1500R/H redundant system
The markings and approvals printed on the components of the S7-1500R/H redundant system
are currently based on operation at an altitude of up to 2 000 m. The fail-safe components
are certified for operation in safety mode up to the specified maximum altitudes (according
to "Z10 067803 0020" certificate
(https://support.industry.siemens.com/cs/ww/de/view/57141281/en)).
Reference
You can find more information in the Mechanical and climatic ambient conditions (Page 490)
section.
502
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF