Which refrigerant classifications are typically regulated under B28?

• A. Mildly flammable only.
• B. All refrigerants regardless of flammability.
• C. Highly flammable refrigerants (A3), such as propane (R-290) and isobutane (R-600a).
• D. Non-flammable refrigerants only.

Answer: (C)

B28 targets the safety risks associated with highly flammable refrigerants. When a refrigerant is classified as A3, it presents a significant ignition and explosion hazard, so codes require strict controls around the design, installation, and operation of systems using these fluids. Propane (R-290) and isobutane (R-600a) are classic examples of A3 refrigerants, which is why they’re described as typically regulated under B28. The emphasis is on managing potential leaks, ensuring adequate ventilation, using explosion-proof electrical components, proper leak detection, and adherence to ignition-source controls.

Nonflammable refrigerants (A1) or mildly flammable ones (A2L) generally fall under broader fire and safety or HVAC codes rather than the specific, heightened protections of B28, so they aren’t the primary focus of this regulation.