Safety

Proven Safety

Solstice yf refrigerant has been verified as safe to use in automobiles through extensive third-party testing, including a three-part Cooperative Research Project conducted by the SAE, and vehicle crash testing conducted by automakers.

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A closer look at some topics raised in the media

Recent media reports in Europe, especially in Germany, have carried shocking headlines and gruesome images about a highly toxic substance, hydrofluoric acid or HF, and the possibility of it being formed from HFO-1234yf in the event of car accidents or fires. It’s time to set the record straight with a series of direct questions and honest answers, grounded in sound science.

Under which conditions will HF be formed?

HF can be formed when fluorocarbons are exposed to surfaces at very high temperatures (700°C) and when combusting (burning) at even higher temperatures. This is true for all fluorocarbons, including the refrigerants R-134a and R-12, which have been used safely in mobile air conditioning (MAC) systems for more than 50 years.

If combusted completely, the theoretical HF yield of one kg of HFO-1234yf is 11 percent less than one kg of R-134a. HF formation has been tested in laboratory conditions by the French research institute Ineris and reported in the SAE CRP1234 (Cooperative Research Project) final report. While SAE has chosen to keep the Ineris attachments confidential, the conclusions of the investigations are presented in the final report.

The formation of HF is strongly dependent on surface temperature, with temperatures below 550 °C producing negligible levels of HF (see page 66, SAE final report). The proportion of HF is dependent on the size and temperature of the hot surface area. Both R-134a and HFO-1234yf produce HF in the same order of magnitude under similar conditions (see page 57 and Table 3-4, page 69, SAE final report).

HF formation was also tested in under hood and interior vehicle tests by Hughes Associates and reported in the SAE CRP1234 final report. While SAE has chosen to keep the Hughes attachments confidential, the conclusions of the investigations are included in the final report. For vehicle interior testing with butane lighters as ignition sources, the entire charge of refrigerant was released into the passenger compartment, and a flame was produced from a butane lighter at the driver’s face location. The HF concentration rose to a maximum of 35 ppm, which is below the Acute Exposure Guideline level 2 (AEGL-2) of 95 parts per million (ppm) for ten minutes (see page 58, SAE final report).

For under hood testing, Hughes set up tests to generate HF on hot engine components and then aspirate the HF into the passenger compartment. Since HF levels were higher when the polyalkylene glycol (PAG) lubricant was present, Hughes applied a nominal oil circulation value of three percent when the oil and the refrigerant were directly sprayed onto the hot surfaces. The hot surface was a 36 cm long and 6 cm diameter steel cylinder. The test was conducted at temperatures of 450°C and 700°C. The mixture was directly applied to the hot surface from a distance of 5 cm to represent the worst possible case. In the worst case, the HF aspirated from the engine compartment into the passenger compartment measured 49.6 ppm. This is well below the AEGL 2 threshold of 95 ppm. In the engine compartment a level of 118.8 ppm of HF was reached (see page 60, SAE final report).

How much HF can be formed theoretically from an average charge HFO-1234yf?

The theoretical maximum is of little relevance since the actual HF conversion is dependent on many other uncontrollable factors. It is generally acknowledged in the chemical processing industry that it is nearly impossible to achieve full conversion. Since HFO-1234yf is released as a gas that is free to flow around and out of the engine compartment, the actual amounts of refrigerant that may pass in close enough proximity to hot surfaces to begin thermal decomposition into HF is very small.

Has the risk of HF formation been tested under real-life conditions? If yes, where are the results?

It is extremely difficult to measure concentrations under real-life conditions, because conditions vary on a multitude of external factors, such as general weather conditions, wind, outside temperature, rain and others. In the context of the SAE Risk Assessment, HF concentrations have been measured using real car models. These measurements are part of the final report, and are summarized in the sections describing the experimental testing at Exponent (page 53, SAE final report) and Hughes Associates Inc. (pages 54, SAE final report).

Can HF be formed in a car crash without the fire?

Theoretically that is possible. In reality, the formation is dependent on so many circumstances that the likelihood is extremely low. The Fault Tree Analysis of the CRP looked at these possibilities: thermal decomposition due to contact with exhaust manifolds and turbochargers in the engine; fires emanating from sources other than the refrigerant; and fires potentially triggered by the refrigerant (see Section 4.5, page 70, SAE final report).

What do we know about the HF concentration in case of a car fire?

The Gradient report (Table 2-5, page 40, SAE final report) explains that HF concentration is dependent on many mitigating variables such as wind, rain, charge size and the release point of the refrigerant. The expected concentrations are on the same order of magnitude as those currently produced by R-134a or historically by R-12; and, as far as we know, there are no records of HF concentrations in car accidents produced from either R-134a or R-12. HF is an irritant and easy to detect at levels of less than 5 ppm, far below the acute exposure limits.

There are thousands of poisonous substances in fires that occur in buildings, airplanes, cars, trains and outdoors. The most relevant ones are carbon monoxide, hydrocyanic acid and substances that irritate the lungs (see Daunderer, Klinische Toxikologie “Brandgase” 143. Erg. Lfg 02/00 p1). Materials such as wool and plastics that are often used in offices, factories, cars and airplanes can release both carbon monoxide and hydrocyanic acid. The theoretical impact of 600 grams of refrigerant in an auto air conditioning system under the hood pales in comparison to the many hundreds of kilograms of plastics, rubber, and foam used in the construction of a passenger vehicle.

Have there been any reported HF-related incidents in car crashes?

To our knowledge no events have been recorded in the 50 years that fluorocarbons or chlorofluorocarbons have been used in car A/C systems.

What risk mitigation measures can be made to prevent HF formation?

The industry has created standards to govern the safe use and construction of heating, ventilation and air conditioning (HVAC) components in the US (SAE J639) and in Europe (ISO 13043). This has been achieved by working with government agencies and approval authorities to ensure the vehicles of tomorrow are just as safe as, or safer than the vehicles of today.
The primary risk mitigation technique to protect the vehicle occupants against exposure to HF or any other gases from the engine compartment is turning off the HVAC blower in the event of an accident.

What about a passenger trapped in a car compartment during a car fire?

HF can only be formed when in contact with surfaces at very high temperatures or when combusting. Tests have shown that these circumstances do not occur in the passenger compartment, but could possibly occur under the hood. The risk assessment shows that HF concentrations in the passenger compartment will remain below the AEGL-2 limit (exposure level that does not result in irreversible damage) and during worst case testing with direct aspiration into the passenger compartment, reached a value of 49.6 ppm (see page 60, SAE final report). Only in exceptional cases might this limit be exceeded; the expected likelihood, however, is a factor 10,000 times lower than that of one being in a plane accident. (Table 4-4, page 90, SAE final report)

Is the HF that is formed consumed in the fire?

HF will quickly dissolve in water used to extinguish the fire and be washed out. In view of the large quantities of water typically used to extinguish a car fire, the concentration levels will be insignificant. HF further reacts with minerals and the road surface to form naturally occurring salts.

What about other toxics released during a car fire?

While we are not experts on car fires, those who are have noted that a car fire produces thousands of hazardous substances. The most relevant ones are carbon monoxide, hydrocyanic acid and other substances that irritate the lungs (see Daunderer, Klinische Toxikologie “Brandgase” 143. Erg. Lfg 02/00 p1). Material such as wool, plastics and foams that are often found in offices, factories, cars and airplanes can release both carbon monoxide and hydrocyanic acid.

Have they been measured in an untreated fire vs. fire treated with water and/or chemical extinguishers?

To our knowledge, no such measurements have been made.

Are there any specific situations that need to be considered in case of tunnels and underground parking garages?

Tunnels and parking garages are special structures that must meet stringent safety requirements. The ventilation systems must be engineered and constructed to avoid the buildup of noxious carbon monoxide and other combustion products, as well as to handle eventualities such as car fires. The SAE risk assessment considered these structures and concluded that based on the mandatory safety precautions they do not warrant additional assessment.

Has flammability been tested under real-life conditions? If yes, where are the results?

Under the EU CLP Regulation (Classification, Labelling and Packaging), a substance must be tested for flammability using a standard OECD test. Based on the test results, the Lower and Upper Flammability Limits have been determined and HFO-1234yf is classified as Flammable category 1. Moreover, extensive additional testing has been conducted by Chillworth Laboratories addressing several critical parameters such as minimum ignition energy, energy of combustion and flame propagation. Based on these parameters, HFO-1234yf has proven to be a very mildly flammable gas compared to propane or gasoline. Under the CRP computer modeling, laboratory testing and in-vehicle testing have been conducted. At least one automotive OEM has conducted a real crash test with no refrigerant ignition.

Ineris performed contract work to determine potential electrical ignition sources in the passenger compartment (Monforte and Caretto, 2009). Based on this work, the SAE CRP concluded the most credible ignition sources are high powered battery shorts (greater than 50 amps), matches, and fires started by other components in the vehicle that are unrelated to the refrigerant.

Ineris and Hughes Associates performed ignition testing on hot cylindrical bodies with flow and geometry variables found in the engine compartment. Ineris found that PAG lubricant itself could be ignited by the hot body at temperatures of 400 °C. Ignition testing with HFO-1234yf alone did not ignite until the hot body was raised above 1000 °C.

Investigations with HFO-1234yf and PAG lubricant at concentrations from 1-7 mass percentage lubricant lowered the geometry dependent ignition temperature of HFO-1234yf to 750 ± 50 °C (see page 51, SAE final report). This temperature was confirmed by testing at Hughes Associates, who found a single ignition at 700°C during engine compartment testing.

According to your SDS, R-1234yf has an auto-ignition temperature of 405°C.

That is correct; the auto-ignition temperature is the lowest temperature at which a gas spontaneously ignites in a homogeneous mixture with air. The auto-ignition temperature is measured in a laboratory set-up, where the mixture is gradually heated up. Such laboratory conditions cannot be duplicated in real-life situations.

Ineris confirmed the auto-ignition of pure HFO-1234yf in the laboratory at 405°C. Upon continued investigation, Ineris found for typical geometries found in the automobile the ignition temperature of pure HFO-1234yf on a hot cylindrical body to be on the order of 1050°C due to flow and geometry variables (see page 26). Investigations with PAG lubricant at concentrations from 1-7 mass percent lowered the geometry dependent ignition temperature to 750 ± 50 °C. This temperature was confirmed by testing at Hughes Associates, who found a single ignition at 700°C during an engine compartment flammability test.

Reference Materials

What dangers are car passengers exposed to in a car using an HFO-1234yf A/C system?

We believe that the risks associated with the use of HFO-1234yf are the same as those currently undertaken by people in the normal use of their cars today. We have shown that HFO-1234yf is difficult to ignite, produces the same amounts of HF when consumed in a fire, and produces approximately the same amount of HF when exposed to hot surfaces. However, if the blower is still intact, turning it off will prevent combustion gases from entering the passenger space.

How have these risks been assessed?

These risks have been addressed by the SAE CRP1234. The members of the CRP risk assessment were all major vehicle OEMs, refrigerant suppliers Honeywell and DuPont, and independent consultants and institutes.

Have these risks been compared to risks associated with the use of systems running on other fluids? If so, what were the results?

The SAE CRP risk assessment has found that using HFO-1234yf does not pose any additional risks above and beyond those that car drivers experience and accept today. The industry has created standards to govern the safe use and construction of heating, ventilation and air conditioning (HVAC) components in the US (SAE J639) and in Europe (ISO 13043). This has been achieved by working with government agencies and approval authorities to ensure the vehicles of tomorrow are just as safe as, or safer than the vehicles of today.

What happens if there is a leak of the refrigerant into the passenger compartment?

In almost all conditions, nothing happens. Leaks caused by corrosion in the air conditioning circuit have been shown not to generate flammable concentrations. In addition, the presence of ignition sources that are large enough to provide sufficient energy to ignite the refrigerant are exceedingly rare and must occur at a specific time during a potential leak scenario.

You have been referring to Fault Tree analysis, but isn’t that too theoretical and not representative of real-life situations?

Fault Tree analysis is used in many instances to determine which events may cause risk and which events will not. While most of us do this to some degree subconsciously in our everyday lives, a true Fault Tree Analysis relies on a structured set of tools. These tools allow users to perform a rationally structured analysis to identify predominate risk scenarios.

What are the dangers that well-intentioned bystanders who try to rescue passengers from a burning car will be exposed to HF?

The amount of HF generated in a collision is not expected to be any worse than the other toxic gases produced by a burning car, such as carbon monoxide and cyanide gas. HF, by itself, is an extremely repulsive gas that a person cannot tolerate even in concentrations below the AEGL-2 level. This will drive well-intentioned bystanders, “Good Samaritans”, away from vehicles involved in a crash and fire. Since R134a will produce the same irritant effect when exposed to a car fire, we expect the same behaviors and reactions as those that occur in bystanders today.

Is there any difference between them and professional rescue workers?

Professional rescue workers have undergone significant training to teach them how to approach many dangerous situations such as car accidents and car fires. They have been taught how to best protect themselves while working to most efficiently remove affected persons from the accident scene.

What protective equipment do you recommend for emergency staff in case of a car fire?

We recommend that emergency staff and professional rescue workers observe and practice their training when responding to car fires. We are making information and services available to any professional organization that requests it. We will also provide additional information to ensure that professional staff has the training to safely respond to vehicle accidents involving HFO-1234yf. The refrigerant charge size in cars is typically less than 600 grams and it should be noted that the safety data sheet (SDS) for R-134a and in fact any other fluorocarbon specifies exactly the same requirement for protective equipment.

In your SDS you prescribe self-contained breathing apparatus and chemical protective suits in case of fires. Is this also needed for car fires?

No, in the case of a fire occurring at a storage site, several tons of material can be released and there is a serious risk of HF exposure at levels well above the AEGL-2 level (95 ppm). This situation is very unlikely to occur in the case of a car fire and no change is indicated compared to the current situation with R-134a in the car A/C. The charge size in cars is typically less than 600 grams. It should be noted that the SDS for R 134a and in fact any other fluorocarbon specifies exactly the same protective equipment requirement.

Have there been any reported HF-related incidents in car crashes?

To our knowledge no events have been recorded in the 50 years that fluorocarbons or chlorofluorocarbons have been used in car A/C systems.

What risk mitigation measures can be made to prevent HF formation?

The industry has created standards to govern the safe use and construction of heating, ventilation and air conditioning (HVAC) components in the US (SAE J639) and in Europe (ISO 13043). This has been achieved by working with government agencies and approval authorities to ensure the vehicles of tomorrow are just as safe as, or safer than the vehicles of today.
The primary risk mitigation technique to protect the vehicle occupants from exposure to HF or any other gases from the engine compartment is turning off the HVAC blower in the event of an accident.