Which of the following is a listed method under the 'other listed methods' category for foam proportioning?

• A. Around-the-pump proportioners.
• B. Inline eductors (inductors).
• C. Balanced positive-pressure injection systems with a variable pump output.
• D. All of the above.

Answer: (D)

In foam-proportioning systems, NFPA 16 designates certain methods as listed for introducing foam concentrate into the water supply, and some fall under the category of “other listed methods.” The methods in this category include around-the-pump proportioners, inline eductors (inductors), and balanced positive-pressure injection systems with a variable pump output. Each of these has published listings and is approved to proportion foam concentrate into the water stream, provided they’re installed and maintained according to the listing and the system’s design requirements. Because all of these approaches are recognized as compliant “other listed methods,” the correct choice is that all of the above are acceptable options.