Refrigerant HFO-1234yf and Flame Retardant Clothing (Part 5)

HFO-1234yf is a Category 1 Flammable Gas.  The manufacturers SDS(s) all say it, as well as 1910.1200 Appendix B. PLEASE see my article Refrigerant HFO-1234yf is a Flammable “4” in the NFPA 704 Diamond (Part 2) for the breakdown of these facts.  With this Cat 1 Flammable Gas comes the hazard of flash fire(s)/explosions.  Now there are some who like to say that this material is “mildly flammable”, a term that is used only when discussing flammable refrigerants.  Refrigerants are classified by ASHRAE as A1 (nonflammable), A2L (mildly flammable), B2L (toxic, mildly flammable), and A3 (flammable).  In ASHRAE Standard 34, the rank “2L” was set up for “mildly flammable refrigerants” with burning velocities lower than 10 cm/s. Together with ammonia, R1234yf is in the “2L” group for flammability; although ammonia is a B2L since it is highly toxic and HFO-1234yf is A2L since it is lower toxicity.  These “safety groups” are based on Flammability (1, 2L, 2, or 3) and Toxicity (A or B).  Here is where HFO-1234yf falls on the scale …

* Except for NH3, refrigerants rated as B for toxicity are not permitted to be used in appliances.

Source: ASHRAE 34-2007, Designation and Safety Classification of Refrigerants

The “official” table is, shown below with the new “L” designation.

I should point out that the Safety Group “L” was a recent edition and made specifically for the new phrase “mildly flammable”.  Ammonia (R-717) used to be rated a B2 before the new safety group was added and it was changed to be a B2L.

Here are some characteristics for the 2L “mildly flammable” refrigerants:

• These are Flammable Gasses by all health and safety standards!
• Requires more than 100g/m3 to burn (typically 300g)
• Heat of combustion less than 19,000 kJ/kg
• Burning velocity less than 10cm/s

A: Low Toxicity

• Permissible exposure limit > 400ppm
• Risk of accidents related to toxicity is low

So I have provided all of this so that you can become very confused and lull yourself into thinking that HFO-1234yf is “mildly flammable”!  This term is ONLY used in ASHRAE safety groupings and not when discussing health and safety terms with respect to OSHA and NFPA.  HFO-1234yf is a Category 1 Flammable Gas; this is the same Category that includes Propane, Butane, etc.  But to be fair, HFO does have a higher LEL than many of the other Cat 1 Flammable Gases, yet an LEL of 6.6% is nothing to brush off.  HFO also has a much higher Minimum Ignition Energy (MIE) than do many of the other Cat 1 Flammable Gases.  Its MIE is around 5,000 mJ, whereas Propane and Butane are less than 1.0 mJ.  And lastly, HFO has a much slower burning velocity of 1.5 cm/s, as compared to Propane @ 38.7 cm/s and Ammonia @ 7.2 cm/s.

So with all this data, does HFO-1234yf present a hazard such that Flame Retardant Clothing (FRC) is necessary?  It is my professional opinion that it does and here’s why I feel this way…

First – Burning velocity may be slow, but 1.5 cm/s is fast enough that no human can outrun the flame front!

Second – 5,000 mJ may seem like a really high MIE, but in reality, a human walking across an ungrounded surface can generate this level of static electricity so although 5,000 mJ is high in comparison to Propane, we can still generate enough static to be an ignition source for HFO-1234yf.

Third – 6.6% LEL is just about the halfway point on the LEL scale for flammable gas (per the definition of a flammable gas), so it is not a low LEL and it is not a high LEL, but the kicker here is that the HFO-1234yf is NON-ODORIZED.  Compare this to ammonia, which has an LEL of 15% and an odor threshold of 5ppm and this equates to having an EXCELLENT warning property to signify that there is a leak and the presence of ammonia. Thus, with NH3 I do not recommend the need for FRC; but PLEASE keep in mind that the ONLY known fatality that occurred within a LEVEL A suit due to the working atmosphere was an FF in Shreveport, LA and he was in an NH3 cloud.  So when you’re wearing a Supplied Air Respirator and we no longer have the ability to detect the presence of NH3 with our senses we have an entirely different situation!!!

With HFO-1234yf, we have NO WARNING properties and a MUCH lower LEL than ammonia.  Because of these reasons, I am suggesting that personnel working in locations in which a flammable atmosphere of HFO-1234yf could be developed and this area does not have the means to detect the HFO-1234yf then FRC is necessary.

From a compliance position, I can almost bet OSHA would expect to see FRC on the Certified PPE Hazard Assessment at those facilities who exceed the PSM threshold of 10,000 pounds.  Since 2006, OSHA has taken the position that a PSM-covered process that is covered because the HHC is “flammable” then FRC should have been identified in the PPE Hazard Assessment.  Seeing how HFO-1234 is a Cat 1 Flammable Gas I am not so sure OSHA will buy the “mildly flammable refrigerant” argument, but I am sure there will be some who try to argue that point.

If the HFO-1234yf was odorized and its odor threshold was MUCH less than the LEL% I would reconsider my position, but it is NOT, and thus I recommend that FRC is worn when working in areas in which a flammable atmosphere of HFO-1234yf could be developed AND this area does not have a means to detect the HFO-1234yf then FRC is necessary.  I would also STRONGLY recommend that FRC be a layer of protection for workers who are opening the HFO process (e.g. line break/process opening), but I have not convinced myself that FRC will be needed for those workers dispensing 600 grams of this material into a vehicle when the dispensing location(s) is equipped with an engineered ventilation system, fixed detectors, and the area is a Class I Division 2 HAZLOC.  But I am open to the debate.

October 2015 UPDATE

The largest manufacturer of HFO has just updated their SDS (9/10/15) with version 2.2 and in this SDS, they state…

Skin and body protection:    Wear suitable protective equipment.  

Wear as appropriate:  

Flame retardant antistatic protective clothing. 

And for those who still do not believe me when I say this material is a Cat 1 Flammable Gas AND therefore its NFPA Fire Rating is a “4”, here some of more data from the SDS:

SECTION 2. HAZARDS IDENTIFICATION  
Product hazard category
Flammable gasses                   Category 1
Gasses under pressure            Liquefied gas