Beware! Decomposing Refrigerants.
For the firefighters who battled the Feb. 16 morning blaze at the Chau Grocery in southwest Houston, the hard work was finished. After managing within half an hour to extinguish the small fire which had started inside a 3-by-15-foot sliding-top display cooler, all that was left was a routine post-operation overhaul.
Dutifully, the firefighters began removing charred debris from the store. Because the fire was out and no other problem was apparent, the firefighters removed their self-contained breathing apparatus. Then strange things began to happen. The firefighters at work reported a tightness in their chests and difficulty breathing. Calvin Mendell, a senior captain with the Houston Fire Department, said the firefighters reported pain that was akin to suffering a heart attack.
Along with chest pain, the firefighters also began complaining of a burning sensation covering their hands, arms and eyes. At least four firefighters were overcome by nausea. Eventually 19 Houston firefighters were affected by the unusual symptoms. At least 11 were transported to a nearby hospital for treatment and observation, four of which were kept overnight. Mendell said firefighters also reported headaches, dizziness and disorientation.
Fire officials later determined that the firefighters had been exposed to hydrofluoric acid, a hazardous material that is potentially lethal. In its most potent form, hydrofluoric acid is the only common acid that can etch glass. Even in its weakest form it can burn the skin and eyes. If it enters the bloodstream it can destroy calcium and magnesium throughout the body. Worse, standard structural firefighting clothing is not completely effective as protection against it.
How did a small fire in a mid-size Houston grocery store turn into a major hazardous materials incident? Officials determined that heat from the fire caused the chemical refrigerant circulating in the cooler to decompose. The firefighters were exposed to toxic vapor leaking from the cooler's sealed system.
"These refrigerants are supposed to be ozone-friendly," Mendell said. "What they fail to tell anyone is that during high heat the chemicals turn into hydrofluoric acid."
Given the right circumstances, an incident similar to what happened in Houston is possible anywhere. Fluorocarbon refrigerants such as the now banned chlorofluorocarbons (CFC), presently used hydrochlorofluorocarbons (HCFC) and the newly developed hydroflourocarbons (HFC) are nonflammable and, to a great degree, stable in gaseous or liquid form. However, all of these refrigerants are toxic substances at the best of times. Add heat from an uncontrolled fire to the chemistry and these refrigerants can quickly break down into their nastiest components. And, as refrigerants continue progressing with the Montreal Protocol-mandated evolution toward the most ozone-friendly compounds possible, the risk from decomposition due to heat is likely to increase.
"Firefighters go into these fires thinking they are dealing with common refrigerants and they're not," Chief Danny Snell, Hazmat coordinator for the Houston Fire Department said.
After the Houston firefighters were overcome, it took four hours to track down a representative of the company that made the brand refrigerant who could identify the problem, Mendell said. Once that representative arrived, firefighters were given strict orders to stay out of the store.
"The medical director basically told us to get out because we could have symptoms from this stuff that would last years," Mendell said.
When the Houston Fire Department's hazardous materials team arrived readings were taken that Mendell said were "off the scale." Although exact figures were not available, Mendell said firefighters noticed an empty 1,000 pound cylinder behind the store.
"The cylinder was suppose to be full, so there was at least that much R-44 in the refrigeration system," Mendell said.
The Houston Fire Department Hazmat team used a six-foot motor-driven airplane propeller to blow fresh air through the structure for the next five hours. Four hours later another reading was taken by the Houston Fire Department Hazmat team, and Mendell said readings were still "off the scale."
Chief Snell said that since the incident all fire department members have been retrained in first responder protocol and are using the fire as a case study for future reference.
"We're still determining whether refrigerants are a true problem or a perceived problem," Snell said. "We're just waiting to find out how dangerous the refrigerants are before any more steps are taken," Snell said.
What happened in that Houston grocery was chemistry, pure and simple. The refrigerant used in that cooler is known under the generic name R-44 (or R-404A), a refrigerant blend consisting of 44 percent HFC-125 (pentafluoroethane), 52 percent HFC-143a (1,1,1-trifluoroethane), and 4 percent HFC-134a (1,1,1,2-tetrafluoroethane). Hydrofluoric acid, which is produced by various refrigerants when they decompose, is a familiar enough agent in modern manufacturing, particularly in the computer chip industry where its dangers are widely known. Citing from "Chemistry of Hazardous Materials" by Eugene Meyer, hydrofluoric acid consists of hydrogen fluoride dissolved in water. The chemical preparation of both hydrofluoric acid and hydrogen fluoride is HF. The industrial preparation often involves the chemical reaction between sulfuric acid and calcium fluoride. In the past, the primary uses of hydrofluoric acid have been to polish, etch, and frost glass, to "pickle" brass, copper, and certain steel alloys, and to serve as either the catalyst or fluorinating agent in certain chemical reactions. More recently, hydrofluoric acid is also being used either directly or as a component of "mixed acid" with sulfuric acid in the manufacture of computer chips. It is also used by petroleum companies to convert petroleum-derived gasoline into high octane gasoline blending stock.
Hydrofluoric acid is a colorless, fuming liquid. Chemically, it is a weak, non oxidizing acid. Nevertheless, concentrated hydrofluoric acid is strongly corrosive to body tissue, producing severe burns that heal very slowly. One example of the worst case scenario for exposure occurred in November 1996 in New York City. A plastic jug of hydrofluoric acid that was left with the routine curbside trash burst open when crushed by a garbage truck compactor, spraying a sanitation worker with a 70 percent solution of the acid. The sanitation worker died soon after exposure.
Medically, even mild exposure to hydrofluoric acid can turn into a physician's nightmare. In the April 1996 edition of Discover, Dr. Jeremy Brown detailed his efforts to save the life of a 37-year-old truck driver who, without wearing gloves, thoughtlessly used a small amount of rust removal product containing the acid. Pain from exposure was almost immediate. Within 40 minutes the victim could not move the fingers on his right hand. However, save for some slight swelling of the fingertips, there was no visible signs of chemical burns.
"When we burn our skin by touching something hot, it is the high temperature that kills the cells," Brown writes. "Chemical burns are different; cells are killed by a chemical reaction on the surface of our skin. Probably the most common type of severe chemical burns come from the sulfuric acid in a car battery. But sulfuric is not the acid to be most feared."
That distinction belongs to hydrofluoric acid, Brown writes. The burn it produces initially creates no blisters or changes in skin color, but it can severely damage the deep tissues of the body. People have died after a patch of skin no bigger than the sole of the foot was exposed to the substance.
Because the hydrofluoric acid molecule lacks a positive charge it can easily pass through the fatty surfaces of membranes. Passing through the tough outer skin, the usually stable bond between hydrogen and fluorine breaks apart. The hydrogen atom binds to enzymes that neutralize acids and keep the pH in our blood and tissue stable. This disrupts the normal chemical balance and kills cells beneath the surface of the skin. Meanwhile, the fluorine binds to calcium and magnesium, minerals critical to a host of electrochemical reactions. Without enough free calcium and magnesium, nerves fail and cell membranes collapse. A mild decline in the levels of these minerals can cause numbness, cramps and horrendous pain. A more severe decline can cause extreme muscle spasms, convulsions, an irregular heartbeat, and even death.
The truck driver was successfully treated for the burn by infusing calcium directly into the radial artery, the artery in the arm that carries blood to the wrist and hand. He later made a complete recovery.
Exposure to escaping refrigerants without fire can be dangerous enough. In 1992 a leak of refrigerant from an Alaska ice-skating rink's compressor room killed one person and injured 34 by asphyxiation. An August report in the British medical journal The Lancet details how a group of gantry-crane operators in a Belgian smelting plant developed liver damage, including acute hepatitis, from lengthy exposure to a blend of HCFC refrigerants escaping into the confined space of the crane's cab from a perforated plastic pipe.
Because refrigerants contain such caustic agents and can cause dramatic health problems under certain conditions it might seem logical that some kind of warning placard be posted, right? Wrong! Under federal law, commercial businesses are not required to alert firefighters or anyone else of the refrigerant coolants used unless more than 10,000 pounds is involved.
"No one is going to have that quantity of coolants unless they are a storage or manufacturing facility," said Danny Snell, hazardous materials coordinator for the Houston Fire Department. "That causes a problem because firefighters exposed to it don't know how the substances break down and the health hazards involved when fighting a fire with refrigerants."
Interestingly enough, if a grocery store kept bottled hydrofluoric acid on the shelves next to the shredded wheat and the alphabet soup the owner would have to post warning placards and submit a material safety data sheet to the local fire department to stay in business. No such action is necessary for refrigerant. The refrigerant R-44, which was involved in the Houston previously mentioned, requires a poisonous liquid DOT (Department of Transportation) placard during shipping and transportation, but no identification is required if the refrigerant is contained in a refrigeration system.
Officials with the Occupational Safety & Health Administration (OSHA) and the Environmental Protection Agency (EPA) maintain that refrigerants are not a threat because the exposure of employees or emergency personnel does not occur under "normal operating conditions."
Under OSHA's 1990 Hazard Communications Standard inspection procedures, certain categories of substances, such as refrigerants, are exempt from coverage because chemicals are only covered if "employees may be exposed during normal operations or in a foreseeable emergency."
Dr. Reva Rubenstein, science advisor for the EPA's stratospheric protection division, said refrigerants developed as an alternative to the now banned CFCs do not present a risk to human health or the environment.
"These refrigerants do not decompose in their environment," Rubenstein said. "We (EPA) don't require warning labels because there is no evidence, as far as we know, that shows refrigerant coolants as being a special hazard."
Neither the EPA or OSHA conducts independent testing of refrigerants under unexpected conditions such as a fire. Instead, the agencies review test data submitted by manufacturers to determine if the refrigerant reduces any overall risk to human health and the environment. The EPA evaluates whether the refrigerant will deplete the ozone layer, contribute to global warming, or present a risk to workers and the general public exposed to it without proper controls. After such an assessment is done, the alternative is listed as acceptable under the federal Clean Air Act.
"EPA does not evaluate the integrity of a product such as a refrigerant under the impact of a conflagration," Rubenstein said.
Whether a firefighter is dealing with CFCs, now banned, or the ozone-friendlier HCFCs, the danger of decomposition from exposure to high heat is about the same, said Jim Nichols, a former chairman of the Tarrant County Junior College fire technology department. All that separates CFC from HCFC is one hydrogen atom. R-12, a CFC predecessor of HCFC refrigerants, is known by the chemical name dichlorodifluoromethane. Ordinary methane consists of one carbon atom surrounded by four hydrogen atoms. Now, replace the hydrogens with atoms from the halogen (salt-producing) group, in this case chlorine and fluorine, and the result is R-12, better known by the trade name Freon.
CFC compounds are far lower in toxicity than refrigerants such as ammonia, and are nonflammable, noncorrosive, and nonreactive with other chemicals. Best of all for manufacturers are the thermal-conductivity and boiling-point characteristics of CFCs. Besides being utilized in refrigeration and air conditioning, CFCs became widely used as a solvent, a propellant in aerosol sprays and as a blowing agent in the production of plastic foams. However, refrigerant remained the leading use of CFCs until the 1990s.
Stability is both CFC's greatest strength and worst drawback. Chlorine compounds from most sources readily combine with water and are washed out of the atmosphere at lower altitude by ordinary rain. However, CFCs do not dissolve in rain. Over time, winds drive the CFCs into the upper atmosphere where they come into contact with the one process that can break down the compound -- exposure to strong ultraviolet radiation. When a CFC molecule breaks down it releases atomic chlorine. One chlorine atom can wipe out more than 100,000 ozone molecules through a process known as photodissociation, destroying ozone faster than it is naturally created.
To solve the problem, scientists came up with HCFC. Instead of two chlorine atoms as in CFCs, HCFCs have one chlorine atom and one hydrogen atom. Adding that hydrogen atom makes HCFCs more susceptible to breakdown in the lower atmosphere, keeping the chlorine from rising high enough to be a threat to the ozone layer.
Although CFCs are by far the least toxic of commercial refrigerants previously used, like any refrigerant gaseous refrigerant containing chlorine and fluorine, they can also yield to corrosive gases during fire situations. This one way in which chemists find CFCs and HCFCs chemical make-ups similar.
"Chemically, there just isn't a lot of difference between CFCs and HCFCs," Barry Lindley, DuPont hazardous materials chemist said. "Any of the halogenated hydrocarbons, if you break them down through temperature, are going to yield halogen acids -- hydrogen chloride or hydrogen fluoride -- which, in a combination with water, forms the acid. The moisture in your system certainly would cause skin irritation, eye irritation and throat irritation. And, especially with HF, if you didn't know it was there, it could lead to death."
The process in which these refrigerants break down to form these ugly compounds is called pyrolysis. During this process a thermal breakdown occurs, breaking the molecules and causing them to reform into the nasty and even deadly chemicals, such as hydrofluoric and hydrochloric acid, that can cause serious damage to humans. These acids can be produced by heat and catalytic metals.
Fires in groceries and supermarkets are common enough. Why aren't more incidents involving decomposition of refrigerants reported? One factor might be the safety features built into refrigeration systems. Ventilation is another factor. Still another might be that symptoms of exposure are attributed to other sources.
In the push to find more environmentally safe refrigerants, the up close and personal shortcomings of some of the potential replacements seem to have been widely overlooked. Anhydrous ammonia, widely used in industry, presents a risk of toxicity, flammability and, in confined spaces, combustion explosion. Yet ammonia is cheap. Propane, another chemical widely used as a refrigerant before the mid-1920s, is also being touted by environmentalists as ozone-benign. The idea is to blend it with another highly flammable hydrocarbon, butane.
Officially, HCFC, with its lessened chlorine and hydrogen additive, is only a temporary replacement for CFC. Under the Montreal Protocol, an international agreement regulating the phaseout of CFCs, a transition is underway to make hydrofluorocarbon (HFC), a refrigerant minus any chlorine and an ozone-depleting potential of zero, the standard worldwide. Industrialized countries will begin a 10-year phasing out HCFCs in 2020. Developing countries will begin phasing out HCFCs by 2040. Another significant difference is that HFCs require a polyol-ester (POE) oil as lubricant, as opposed to the alkyl benzene based oil used by HCFCS and the minerals based oils used by CFCs. The polyol ester oil is made by combining a fatty acid with alcohol to form the ester, with water being a residual compound in the reaction. When the moisture content exceeds 75 ppm, an acid is formed in the oil; the greater the moisture content, the greater the acid formation.
HFC, as much a halogenated hydrocarbon as CFC or HCFC, may be safer for the distant ozone layer, but at close range firefighters will face a greater threat from heat decomposition. Lindley said that the main difference between HFCs and the other refrigerants is the excess of hydrofluoric acid produced by the fluorine in HFC.
"As far as toxicity and reaction in fire situations goes they're all about the same except HFCs produce a lot more hydrofluoric acid," Lindley said. " Not only is hydrofluoric acid more dangerous to humans than hydrochloric acid produced by CFC and HCFC it takes lower concentrations, it takes much lower concentration of hydrofluoric acid to cause serious damage."
Tests done by industry suggest that the level of decomposition from heat for an HFC is increased by a factor of 10 over CFC or HCFC. The bond between carbon and fluorine simply is not as strong as the bond between carbon and chlorine.
Capt. Royce Beck of the Houston Fire Department has been a firefighter for 31 years. He said he believes that the new refrigerants are more dangerous than the old ones in a fire situation.
"We just jumped into something without doing enough research," said Beck. "They may be better for the environment, but not the emergency personnel that respond to them."
With the food industry as a major refrigeration user, 78,000 giant centrifugal chillers, 1.7 million food display cases and 3.8 million institutional food coolers and freezers, the disappearance of refrigerants is unlikely. Not only are refrigerants found in commercial use they are found in personal automobiles and refrigerations systems. As society becomes increasingly environmentally conscious, industry will probably see several new forms of refrigerants appear in the next couple of years. Emergency personnel and refrigeration facilities need to be aware of what refrigerant they're dealing with and anticipate emergencies. Along with getting thorough knowledge of the subject, purchasing leak detection equipment, replacing refrigerations systems and proper training are steps that should be taken to ensure personal safety in an emergency involving refrigerants. Research is continually being done to develop a safe alternative such as vapour compression, thermo-electric and magnetic refrigeration, but in the meantime emergency personnel needs to prepare and anticipate.