Refrigerant Safety Group Chart (A1, A2L, A3, B)

What it is

Every refrigerant listed in ASHRAE 34 (and ISO 817) gets a safety group made of a letter and a number. The letter is the toxicity class. The number is the flammability class. A1 is the lowest-hazard group. B3 is the highest. The safety group drives which codes, charge limits, equipment listings, cylinder markings and handling rules apply.

How to read it

• Letter A means lower toxicity. Letter B means higher toxicity. The split is based on the occupational exposure limit, with 400 ppm as the dividing line.
• Number 1 means no flame propagation in the standard test.
• 2L is a subclass of 2: lower flammability with a low burning velocity (10 cm/s or less). Hard to ignite, but it can burn.
• 2 means flammable.
• 3 means higher flammability (low flammable limit or high heat of combustion).
• Find the group on the equipment nameplate, the cylinder label or the refrigerant SDS.

Safety group chart

Key points

• A1 does not mean harmless. Any refrigerant can displace oxygen in a closed space. High concentrations can cause heart rhythm problems. Some decompose into toxic products in a flame.
• A2L units need A2L-rated tools and procedures. Recovery machines, leak detectors and vacuum pumps must be rated for the refrigerant in use.
• Blends get one group for the blend as formulated. Some also carry a worst-case fractionation rating. Check the SDS.
• The group is not the same as the GWP or the code charge limit. Those come from other tables in the codes and the equipment listing.

Common mistakes

• Treating A2L like A1 because the letter is the same.
• Reading the toxicity letter as a flammability rating.
• Assuming a new low-GWP refrigerant is a drop-in for an A1 system. The safety group and listing must match.

Governing standards: ASHRAE 34 (designation and safety classification); ISO 817 (international equivalent); ASHRAE 15 and the adopted mechanical code for application rules; the refrigerant SDS and equipment listing.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.