Which of these options is the most secure procedure for storing backup tapes?

Storing backup tapes in an offsite climate-controlled facility satisfies two critical requirements simultaneously: environmental controls (regulated temperature and humidity prevent tape degradation and data loss) and geographic separation (ensures backups survive a catastrophic event such as fire, flood, or power failure that destroys the primary site). This combination is the industry-standard best practice defined in contingency planning frameworks like NIST SP 800-34.

A cool dry environment protects against media degradation but does not provide offsite geographic separation, leaving backups exposed to the same site-level disaster that could destroy the primary systems.

Storing tapes on a different floor of the same building still subjects them to building-wide disasters such as fire or structural collapse, which defeats the purpose of maintaining a separate backup copy.

Keeping tapes inside the data center in a fireproof safe does not satisfy the offsite requirement, meaning a site-level disaster could simultaneously destroy both the production systems and the backups.