What is NFPA 11's stance on mixing foam concentrates from different manufacturers?

• A. It allows it freely
• B. It prohibits it entirely
• C. It allows only under AHJ approval based on manufacturer data
• D. It requires identical packaging

Answer: (C)

NFPA 11 treats foam concentrates as chemistries that must work together with the equipment and system they’re used with. Because different brands can have different formulations, mixing concentrates from different manufacturers isn’t something you do by guesswork. The standard allows blending only when the Authority Having Jurisdiction approves it, and that approval must be based on data provided by the manufacturers showing the blended concentrate is compatible and will meet required performance. In other words, you don’t mix unless there’s documented compatibility and performance evidence the AHJ finds acceptable. Packaging identity isn’t the controlling factor; the key is documented compatibility and tested performance.