It does not cover oil-fired heaters, water-tube boilers (covered by NFPA 85), or specialty units like pyrolysis furnaces or CO boilers. Key Sections of API RP 556
, titled "Instrumentation, Control, and Protective Systems for Gas Fired Heaters," provides the definitive framework for managing these risks through standardized design and operational practices. Scope and Application api rp 556 pdf
Instrumentation, Control, and Protective Systems for Gas Fired Heaters It does not cover oil-fired heaters, water-tube boilers