This page is a supplement to the paper Some Safety Studies of a Ternary Refrigerant. R-406A has been safety classified by ASHRAE as "A1/A2". This means (as formulated / worst case), and for R-406A, is "lower toxicity group, non flammable" as formulated / "lower toxicity group, lower flammability group" after worst case leakage.
You will see HCFC refrigerants being "vented" here for R&D purposes. Craig Haas of the US EPA Enforcement Division has clarified that R&D purposes (such as safety testing) do not fall under the venting prohibitions of the Clean Air Act, Sections 608 & 609.
The 2nd character of
the classification is the flammability classification (1 = non
flammable, 2 = lower flammability group, 3 = higher flammability
group). As formulated, R-406A is totally non flammable, neither
vapor nor liquid will burn. If leakage occurs (from a vapor
region), the composition will change. At somewhere between 40-50%
and 90-100% of total leakage (mass loss), the remaining charge
may become WEAKLY FLAMMABLE.
The point at which the weak flammability zone is entered depends primarily on the temperature during the leaking process. Cooler temperatures will cause the zone to be entered earlier, and warmer temperatures will cause the zone to occur later or not at all. Cooler leakout (fractionation) temperatures only cause the zone to be entered earlier, they do not appear to increase the severity of the flammability (it always stays "weak"). In anycase, the end product of a worst case leakdown is R-142b. The R-600a (isobutane) is gone before the end is reached, and is inhibited by remaining R-22. This chart is vapor composition by volume (headspace above the liquid), not liquid composition by weight. That is why the R-22 starts out at 70% instead of 55% as given in the formulation. (leakout at 68F)
Click on each of the images to see a larger, more detailed
version. These images all came from video. The first example
(left) is virgin (as formulated) R-406A, vapor, blowing through a
propane torch flame. Nothing happens. On the right, is R-406A
"liquid" venting from a cylinder into a propane torch
flame. Nothing happens. Now and then a small "sparkle"
occurs from decomposition of the refrigrant in the flame.
Left, R-406A liquid spill on the ground, boiling vigorously. As
the torch flame is brought into the area above the spill, some
decomposition (small yellow flame area) occurs (does not spread
or continue without the torch being present), and the torch is
extinguished. Right, a special (weakly flammable) cylinder is
made up of what R-406A turns into after it has vapor leaked out
about 95% (at 70F), to simulate worst possible conditions. This
composition is (% wt) 3/84/13 R-600a/R-142b/R-22. Vapor, liquid,
and liquid spill tests are done on this "worst case
mixture".
Left, a propane torch is placed in a stream of worst case
composition R-406A vapor venting. A small amount of flame is seen
near the torch only. It does not propagate nor burn on its own
with the torch removed. Right, a propane torch is placed in a
stream of worst case composition R-406A liquid venting. A small
amount of flame is seen near the torch only. It does not
propagate or burn on its own with the torch removed. Now and then
a small "puff" of flame will form, and extinguish
itself. Neither venting jets of R-406A worst case composition
vapor nor liquid will ignite and stay lit. Pure R-142b (at 100%
leakout) exhibits similar behavior. There is no "flash
point".
Left, liquid Spill of R-406A after (worst case) leakdown (8 fluid
oz in a beaker), can be ignited with a propane torch, and will
stay lit for about 2 seconds, and self extinguish. Flame stays in
the beaker for the most part. Pure R-142b exhibits similar
behavior. Right, liquid spill of R-406A after (worst case)
leakdown (8 fluid oz in a beaker dumped onto the ground - boiling
vigorously), can be ignited with a propane torch, and will stay
lit for about 2 seconds, and self extinguish. Pure R-142b
exhibits similar behavior.
Left, pure propane (R-406A never does anything like this) vapor
being vented, ignites and easily sustains with ignition source
removed (same propane torch). Right, propane, 8 fluid oz, liquid
spill on ground. Easily ignited and sustains with ignition source
removed. Fire totally engulfs the area. If spilled first, and
later ignited, an explosion is likely. Many competitors describe
R-406A as this case, which simply is not true. The difference
between weak "class 2" flammability and "class
3" is easily seen. The small "dark" area, near the
center at the "bottom" of the fire is the beaker. This
pix was taken about 50 feet away for obvious reasons.