Should I Worry About ‘Mildly Flammable’ HVAC Refrigerants?

You may have heard that the HVAC industry is going through a big refrigerant change. What does this actually mean?

A refrigerant is the chemical inside your air conditioner or heat pump that moves heat from where you don’t want it, to where you do. It’s what makes cooling possible.

The new generation of refrigerants (like R-454B) have a much lower global warming potential. In fact, it’s about one-quarter as potent as the older R-410A. Because refrigerants contribute significantly to a building’s embodied carbon, this shift is a meaningful step toward more sustainable homes.

What’s the catch?

These new refrigerants are classified as “mildly flammable” by ASHRAE. They fall into the A2L category. “A” means non-toxic, and “2L” refers to a low level of flammability. Scary? No, as this is well below something like propane, which is classified as highly flammable (3).

A2L refrigerants don’t behave in the same way that a propane grill or a blowtorch do. They don’t simply ignite and keep burning with a match. In fact, under normal conditions (even in the case of a leak) the concentration typically won’t reach flammable levels.

We’re already comfortable with propane grills on our decks and natural gas running through our homes. A2Ls deserve this same level of practical perspective… while still being handled with proper safety protocols.

What does this mean for builders?

Honestly, not much, assuming your HVAC contractor is properly trained and EPA-certified. Technicians need the right tools that are rated for A2Ls and should follow best practices for charging and servicing equipment. Modern systems also include built-in safety features that can detect leaks, shut down the compressor, and run the fan to help dilute refrigerant if needed.

Bottom line

The name sounds more dramatic than the reality. A2L refrigerants are a responsible step forward for sustainability, with manageable and well-understood safety considerations.