The American Petroleum Institute’s publication store (publications.api.org) is the safest, most reliable source. As of this writing, the PDF of API RP 2030 4th Edition is available for purchase (typically $150–$250 USD depending on member status).
: Principles for determining where water spray systems are necessary and how they differ from standard sprinkler systems. api rp 2030pdf full
A: Best practice is to use the latest edition. Outdated versions may reference obsolete technologies (e.g., non-UL-listed spray nozzles) and could expose you to liability in a lawsuit. api rp 2030pdf full