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July 1996 By Stephen Saunders Toxic Cabling Cabling: What You Don't Know Can Kill You Halogen cabling can emit toxic fumes in a fire. Many international governments have moved to less lethal alternatives . Why hasn't the U.S. done the same? [ Up in Smoke? | The Insurance Angle ] There's something corporate networkers should know. Most of the cable they're now pulling at central sites and branch offices across the U.S. contains halogens--chemicals that give off toxic fumes when they burn. In a fire, halogen cable can release acid gases that sear the eyes, nose, mouth, and throat. The fumes can disorient victims, preventing them from escaping the blaze. They can cause severe respiratory damage. And they can kill. Recognizing this potentially deadly problem, a number of international governments have already standardized on zero-halogen cabling. But the U.S. National Electrical Code, which serves as the basis for local standards in 45 states, effectively forces net managers to use halogen-sheathed Category 5 UTP in the plenum spaces above ceilings and below floors in office buildings. And while some organizations that are exempt from local building codes--like the military and mass transit authorities--have banned halogen cabling from their networks, most net managers have little choice but to obey the law. And that, argue halogen-free advocates, could be fatal. Building plenums are typically used to circulate air throughout the workplace. If there's a fire, they warn, heating and air-conditioning ducts could become conduits for hydrogen chloride, hydrogen fluoride, and the other gases that cause far more fatalities than flames or visible smoke. Life and Breath For some critics, the difference between international and U.S. standards reveals stark contrasts. "U.S. cabling codes are designed to save property. In Europe we are more interested in saving lives," says Dario Erba, manager for structured cabling a t IBM Europe (Vimercate, Italy), which installs only acid-free cable. Erba's assessment may strike many as unduly harsh, but it raises an important concern: Given halogens' lethal potential, why are they used in cabling at all? There's actually a method to this apparent madness. Halogens are an extremely effective fire retardant. Adding them to cable insulation increases its kindling point. "If the cable doesn't catch fire, it won't give off toxic fumes," says Loren Caudill, senior development specialist for codes and standards at DuPont (Wilmington, Del.). The chemical company is the leading manufacturer of FEP (fluorinated ethylene propylene), the most toxic halogen and the one used in the majority of cabling. No Easy Answers It's a deadly double bind: Halogen insulation helps prevent cables from catching fire, but if the cable jackets do ignite the resultant fumes can drive up the death toll. And this dilemma has been at the heart of a decade-long debate about the continue d use of halogen. "Fluorinated polymers are hundreds of times more toxic than zero-halogen cabling," comments Marcelo Hirschler, a consultant with BGH International Inc. (Mill Valley, Calif.), a firm that specializes in fire-safety issues. "They're also far less flammable." To date, halogen's defenders, which include DuPont and B.F. Goodrich Co. (Akron, Ohio), have carried the day. But the opposition, whose ranks include manufacturers of zero-halogen cable, is turning up the heat in hopes of convincing the National Fire Protection Association (NFPA, Quincy, Mass.) to change the current code. The amended standards will go into effect in 1999, but the deadline for filing proposed changes is late this year. This isn't the first time that halogen-free advocates have tried to alter the law, looking to ban halogen outright or allow zero-halogen cable to be used in building plenum. Thus far they've failed, partly because the onus is on the opposition to demonstrate that halogen-free cable will saves lives. That's been particularly difficult to do given that both types of cable--halogen and halogen-free--produce carbon monoxide when they burn. And carbon monoxide is the leading cause of death in fires. "There was a lot of argument about this six years ago, but the people in favor of zero-halogen couldn't prove their case," says Dave McCormack, assistant to the president of the International Association of Firefighters (St. Louis). McCormack believes the code should be changed to restrict the use of halogen cabling, which some tests show to be more than five times as toxic as its acid-free equivalent. Catastrophic Corrosion This time around, however, the anti-halogen forces are taking a different tack. They now argue that these chemicals should be outlawed because of the catastrophic effect acid fumes have on computer circuitry--causing millions of dollars worth of damage even in small fires. "Corrosivity is the Achilles' heel of halogen cables," comments Michael Keogh, corporate fellow at Union Carbide Corp. (Danbury, Conn). "It's a matter of machine toxicity, not human toxicity." Union Carbide makes the raw materials used in both halogen and halogen-free cable. And where does all this leave net managers interested in eliminating halogen from their networks? Unfortunately, they don't have many options. The law is clear: Meet the code or risk the consequences, which range from being fined by building inspectors or fire marshals to insurance companies that refuse to pay up in the event of a disaster (see The Insurance Angle ). Switching to fiber makes no difference, because its insulation is subject to the same code as copper. About the only way to legally install halogen-free cable is to run it in metal conduits. Trouble is, these conduits typically double the price of a cabling system. Standards Schism International cabling standards were developed in response to events in the Falklands War. Research showed that most shipboard fatalities during the conflict were the result of the smoke from fires started by missiles and bombs rather than by the weapons themselves. "Acid gases also prevented personnel from fighting the fires," says Karen Long, a physicist at the Naval Sea Systems Command (Washington, D.C.). Long is responsible for developing fiber cabling standards for the U.S. Navy, which has decided to go halogen-free. Many countries--including Australia, France, Italy, Japan, Korea, New Zealand, and the U.K.--have also moved to halogen-free cabling. And even in countries where the choice of cable is still left to the installer, zero-halogen is becoming the technology of choice, according to IBM's Erba. "Halogen-free cables account for 40 percent of the total communications cable in Europe," he says. He believes that the remaining 60 percent is halogen-sheathed PVC (polyvinyl chloride). The easiest way to see the difference between international and U.S. cabling codes is to compare what they cover. Inter national standards address three issues: fire resistance (how fast cable burns); smoke density (how much visible smoke is produced); toxicity (how harmful the smoke is to human beings). U.S. codes, in contrast, only address two of those criteria: fire resistance and smoke density. The National Electrical Code is silent when it comes to toxicity. This is by design, not omission. "We try to stay out of health-related subjects. We're electricians. We're not in the health business," says Joseph Sheehan, senior electrical specialist with the NFPA. It should be noted, however, that the U.S. standards for fire resistance are more comprehensive and more stringent than their international counterparts. Three levels are defined. The first and least demanding applies to general-purpose cabling (such as that used to connect a phone to a wall jack). The second applies to cables installed in building risers. The third and toughest code is reserved for cabling installed in plenu m spaces. Chemical Conditioning The only way to meet the more demanding U.S. standards is to add one of several halogens to the polymer plastic used in cable insulation. PVC cable contains chlorine; FEP (also known as Teflon FEP) is made with fluorine. FEP is highly fire-resistant. It can withstand temperatures to 800° before it begins to break down. It's also an extremely efficient electrical insulator, which suits it to cable that carries high-speed data. Those two characteristics have made FEP the key component in plenum-rated Category 5 UTP (unshielded twisted-pair) in the U.S. What's more, FEP cabling has largely replaced PVC cable in building risers and elsewhere, despite the fact that it's only legally required in plenums. It's a different story overseas. In order to meet rigorous international toxicity specs cable manufacturers avoid halogens altogether, instead adding metal hydrates to their polyethylene and polypropylene cable insulation. When heated, these che micals release steam. But halogen-free cables made with metal hydrates are not as fire-resistant as their U.S. counterparts. And once the metal hydrate is exhausted, the insulation burns freely. Zero-halogen cable meets the two less stringent U.S. fire-resistance standards. It's acceptable for general-purpose use and for building risers. But in order to obtain a plenum rating manufacturers would have to add so much metal hydrate to their insulation that the cable would no longer meet Category 5 UTP electrical requirements. "The flame retardant additives," explains Keogh, "do not have good electrical properties." Trying to sell lower performance Cat 3 or 4 cable into U.S. markets would be an exercise in futility. Corporations are now moving to higher speed LANs and need the superior electrical properties of Cat 5 cable to cope with bigger bandwidths. Burning Issues When the PVC cables used in building risers burn they emit both hydrogen chloride (an acid gas) and dioxi n, which Greenpeace, the environmental advocacy group, calls "the most toxic synthetic chemical known to science" (see Table 1). Long-term exposure to dioxin has been linked to a number of health problems, including cancer, reproductive disorders, birth defects, impaired neurological development, diabetes, and immune system suppression. Table 1: Insulation Issues Cable insulation Performance rating/ top data rate Plenum approved Cost per 1,000 feet Characteristics By-products when burned Toxicity rating (LC50)* Halogen FEP (fluorinated ethylene propylene) Category 5/100 Mbit/s Yes $275 Low smoke, high toxicity; highly fire resistant Hydrogen fluoride, carbon monoxide LC50 range = 36.1 to 77.1 Halogen PVC (polyvinyl chloride) Category 3/10 Mbit/s No $100 High smoke, high toxicity; low fire resistance Hydrogen chloride, dioxin, carbon monoxide LC50 range = 10 to 20.6 Halogen-free (various metal hydrates) Category 5/100 Mbit/s No $160 Low smoke, low toxicity; fire resistant until metal hydrate exhausted Steam, carbon monoxide LC50 range = 4.4 to 15.6 * Toxicity is measured using the LC50 rating, which indicates the number of grams of insulation that must be burned to kill half the mice in a lab experiment. LC50 ratings supplied by the State of New Yorkís Hazardous Materials Bureau. When FEP cable burns it releases hydrogen fluoride, an odorless invisible gas that is considerably more toxic than hydrogen chloride. Tests conducted at University of Pittsburgh in the 1980s also indicate the presence of another, far more deadly gas, in FEP fumes--known in the cable industry as "the supertoxin." Some scientists theorize the gas is a fluoro-phosgene--the fluorine equivalent to the phosgene gas used in World War I. The supertoxin was never properly identified, and resear ch into it has now ceased. "We know there's hydrogen fluoride, but that's not the real problem," says BGH's Hirschler. "There's something else in the gases, and nobody knows what it really is except that it's highly, highly toxic." Not all researchers agree with Hirschler's assessment. "Most people have largely put the supertoxin down as a laboratory phenomenon, not a real-world phenomenon," says Edward Weil, professor at Polytechnic University (Brooklyn, N.Y.), which conducts research into halogen and halogen-free cabling. FEP's poisonous potential has prompted some grisly jokes at cabling companies. "The advantage of fluorine cable is that the firemen can see your body and step over it when they arrive to put out the fire," says Paul Chalifour, senior manager of market development at Nordx/CDT, a subsidiary of Cable Design Technologies Corp. (Pittsburgh). Like almost all cable companies, Nordx sells halogen and halogen-free cabling. Learn Not To Burn Champions of halogen-fr ee cable are quick to point out that in a fire what can't be seen is far more lethal than what can. Invisible gases given off by burning material are the cause of more than 80 percent of fire deaths, according to research published in the British Medical Journal . In the U.S. that translates into as many as 6,000 deaths a year. And halogen's opponents are sure that the chemicals are killers. Most of the available data on cable toxicity was gathered after the State of New York changed its building code in 1988, requiring that all cabling products be tested for toxicity--the only state ever to do so. The tests were conducted by Anderson Laboratories (West Hertford, Vt.) on behalf of the National Electrical Manufacturers Association (NEMA, Rosslyn, Va.). Anderson Labs measured cable toxicity on mice in a laboratory using the so-called Pittsburgh Test (named for the university where it was developed). In the test, a specific amount of insulation is burned, with the fumes shunted throug h a tube to four mice. This procedure is repeated with more insulation until two of the mice are dead. The insulation is then assigned an LC50 (life count 50) toxicity rating that indicates the number of grams of insulation that had to be burned to kill half the test animals. The higher the LC50 rating, the less toxic the cable. Over 1,000 tests were conducted. Data Communications obtained the LC50 ratings from the State of New York's Hazardous Materials Bureau (see Figure 1). They show that halogen FEP cable is more than 5 times as toxic as halogen-free and 1.5 times as toxic as halogen PVC. Figure 1: Deadly in Small Doses Exposing laboratory mice to the fumes produced by burning insulation makes it possible to measure cable toxicity. The LC50 rating indicates how many grams of insulation had to be burned to kill two of the four mice in each round of tests. The lo wer the rating, the more deadly the fumes. The results show that FEP cable is more than 5 times as toxic as its halogen-free counterpart and roughly 1.5 times as deadly as PVC cabling. Fep Fightback The NFPA, the nonprofit association that oversees the national code, doesn't dispute FEP's lethal nature. "If the plenum tests were based only on toxicity, Teflon FEP is probably the only material that would not pass," says Arthur Cote, vice president and chief engineer. "It's an order of magnitude higher in terms of toxic potency than almost any other material in use today." But Cote, who also is secretary of the NFPA's toxicity advisory committee, doesn't think the code should be changed, citing doubts about the Pittsburgh Test methodology. Other halogen advocates also challenge the test results . Some argue that the findings are academic because the tests don't mirror real-world conditions. "By the time the levels of heat in a building were high enough to release those gases, everyone would be dead anyway," says Al Scolnik, vice president of power distribution products at NEMA and former director of NEMA's wire and cable division. Halogen defenders also argue that autopsies of fire victims usually show carbon monoxide poisoning as the cause of death--not hydrogen chloride or hydrogen fluroide. And they add that cables only contribute a small amount of smoke to a fire. Computer simulations by the National Research Counsel of Canada suggest that less than 12 percent of the smoke comes from cable. The anti-halogen forces have answers ready on all counts. For one thing, they argue that while carbon monoxide poisoning may be the direct cause of death in a fire, acid gases can disorient victims and prevent them from escaping a burning building. What's more, they assert that where cable is located is just as important as the smoke it gives off. Since building plenum is typically used by the air-conditioning system, wiring ducts can distribute toxic fumes throughout the workplace--even if a fire hot enough to release the fumes is restricted to a small area. "If there's smoke in the plenum return it can be sucked back and redistributed," explains Mike Kerwin, principal at Cablenet System Inc. (Woburn, Mass.), which installs cabling systems for corporations and educational organizations. The Düsseldorf Disaster That appears to be what happened during a fire at Düsseldorf Airport in Germany last April in which 16 people were killed and more than 60 hospitalized for smoke inhalation. The fire appears to have been sparked off by welders working in a combined ventilation and cable shaft in the main arrival hall. According to the British newspaper The Independent , "PVC-covered cables began to smolder, emitting cyanide, chloride, carbon monoxide, and poss ibly dioxin fumes that spread through the building's ventilation shafts." The International Herald Tribune reported that the "fire carried a flood of lethal fumes into elevators, ventilation ducts, and passenger lounges." That sort of disaster makes halogen opponents understandably nervous--especially since there's far more cable in building plenums than ever before. "There wasn't much wire above ceilings 10 years ago. Since then, the amount of cabling has gone up by several orders of magnitude," says Richard Bukowski, senior research engineer at the building and fire research laboratory of the National Institute of Standards and Technology (NIST, Gaithersburg, Md.). "The bigger the fuel load, the bigger the concern over fumes," he adds. "There should be controls on where you can use halogen cable. The last place you want it is in a plenum. If you must run it there it's essential that it's contained in a rigid conduit or pipe," says McCormack of the International Association of Fi refighters. He notes that conduit is compulsory in only two U.S. cities: Chicago and New York. Playing Politics Critics of halogen cable also argue that cable manufacturers and chemical companies have a vested interest in maintaining the status quo. FEP cabling is about 40 percent more expensive than halogen-free. DuPont has even more to lose; it has an almost total lock on the FEP market, accounting for over 90 percent of production. Some observers claim that the big cable and chemical manufacturers have used undue influence to prevent code changes. "The only reason we can't spec halogen-free is because of political maneuvering by the cabling companies," says Allen Kasiewicz, president of Trellis Communications Corp. (Manchester, N.H.), a cabling installer and consultancy. But evidence backing up those charges is virtually nonexistent. And it's worth noting that the NFPA limits the number of panelists from any one organization to prevent packing the committees that discuss c ode changes. Of course, there are loopholes. As well as its official delegates, DuPont staffers attend NFPA meetings under the guise of the Chemical Manufacturers Association. Still, its representatives only make up a fraction of the 400 people that are involved in the review process. The Acid Test As indicated, zero-halogen advocates are gearing up for a new campaign aimed at amending the next edition of the national code. But rather than once again taking the toxic tack, the latest push focuses on the catastrophic damage that smoke can cause to computer and networking equipment. "It's the next big battle," says Tom Ebert, engineering group leader at Underwriter's Labs Inc. (Elkhart, Ind.), which is developing a new corrosivity test. Both sides agree that there's a problem. "There are numerous examples of multimillion dollar damages after even a very small PVC fire," says Poul Villien, coordinating manager at 3P Third Party Testing (Hoersholm, Denmark), an independent test facility. "Even a smoldering fire can wreak havoc on a modern office. It doesn't have to be big enough to set off the sprinklers," agrees Tom Chapin, member of the technical staff at Lucent Technologies (the recent AT&T consolidation, Murray Hill, N.J.), which sells both halogen and halogen-free cabling. The Burden of Proof Despite the apparent agreement, it's by no means certain that the latest bid to permit the use of halogen-free cable in plenum airspace will be any more successful than earlier efforts. Once again, it's up to the advocates of change to prove that halogen-free cables are safer--although this time the debate centers on hardware rather than human beings. And the pro-halogen group is already preparing its counteroffensive. What may make the anti-halogen push even harder is that there's less consensus on gauging corrosivity than there is on measuring toxicity. Currently, there are about 20 different tests used worldwide. In Europe, cable corrosivity is gener ally matched to the PH value of the gas that's emitted when the insulation burns. (Levels of 1 to 4 are deemed corrosive, levels of 5 and above are not.) When PVC burns it produces hydrogen chloride, which has a PH level of 1. When FEP insulation burns it releases hydrogen fluoride, which has a PH level of 3 to 4. When halogen-free cables burns it gives off steam, which has a PH level of 6.5 to 8.5. But some observers believe PH values are only part of the story. "Smoke particles can have a traumatic effect on closely spaced electronic components on a circuit board. And the PH test doesn't measure the highly conductive ionic contaminants that can be produced when cable burns," says Chapin. Lucent has come up with a new test--called an interdigitated comb pattern--that it claims more accurately emulates the effects of fire on a PC board. The test bed comprises two interleaved copper combs. Smoke is passed across the combs, and the amount of electrical leakage is then measured. Chapin sa ys test results show that going with zero-halogen cable doesn't guarantee fewer problems. "Some of the halogen-free cables are great. But some of them approach the corrosivity of halogen cabling." Given that finding, Chapin recommends that net managers wait for cross-comparison testing of cables to be performed and the findings published before opting for any particular brand. But with so many different tests in use, net managers still have the problem of whose results to trust. In the end, it may take more than testing, lobbying, or even common sense to force a change in the U.S. codes. "There's an on-off attitude about fire safety," says Rosalind Anderson, president of Anderson Laboratories. "If you haven't killed anyone important recently, then it's not an issue." Stephen Saunders is news editor for Data Communications. His e-mail address is ssaunder@data.com . 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