The Nagging Creosote Problem
UL 1482 enjoys wide support. Unlike UL's standards for fireplace inserts and metal chimneys, it has not been controversial within UL.
Insurance companies and various independent consultants endorse the standard without qualification. Even the CPSC concluded, at least unofficially, that the standard is adequate in all respects save some minor labeling provisions. A few manufacturers have voiced opposition to UL 1482, but their complaint, contrary to what might be expected, is that the standard is too lax. Anticompetitive motives apparently explain the opposition in one case. More typical of those who do not actively endorse UL 1482 is the view of a woodstove consultant who thinks that "listing under 1482 has little or nothing to do with safety." This is not an indictment of UL's standard so much as an expression that standards per se have little effect on woodstove safety.
While that may be true in general, one of the only substantial complaints about UL 1482 is that it should cover a problem it largely ignores: creosote. The standard has no provisions for evaluating the tendency of a woodstove to create creosote. In fact, the existing test procedures intentionally "control for" the two major causes of creosote formation: low burning temperatures and high-moisture wood. All of the fire tests are conducted when the stove is burning its hottest, and the "test wood" is much drier than seasoned firewood, often with a moisture content approaching zero. It has been argued that these performance tests may actually encourage greater creosote formation in stoves, at least when they are used under normal conditions. In other words, design changes that might help bring a stove into compliance with UL's temperature limits can, according to several woodstove consultants, also increase the stove's tendency to produce creosote in the real world. Whether the standard has actually prompted such design changes is not known.
UL claims that it cannot test for creosote. "We would test for [it] if there was a way to do it," according to a UL engineer familiar with the myriad factors affecting creosote formation. To be sure, just switching to wood with normal moisture content would pose big problems. It is much harder to standardize wood at a moisture content of, say, 20 percent than at percentages approaching zero. Creosote formation is also a slow process, raising the specter of long and involved test procedures. Tests for compliance with UL 1482 can be accomplished in a few days. The NBS spent several months of constant firing for its measurements of creosote formation.
Although these difficulties are not trivial, neither are they insurmountable or of a nature very different from the problems attendant to most product testing. There is a way to test for creosote formation. One
independent laboratory already conducts such tests (not for certification purposes, but as a consultative service). Similarly, there is an established test procedure for measuring woodstove efficiency—a factor directly related to creosote formation. The test uses high-moisture wood and is being performed without difficulty by the same lab.
So why doesn't UL do it? The short answer is that there is insufficient demand. Inside UL there is a feeling that creosote formation is a user problem, not a product problem. UL argues that the tendency to create creosote is irrelevant if the user avoids wet wood, monitors burning temperatures, and has the chimney cleaned whenever indicated through regular inspections. This philosophical position is reinforced by practical considerations. Including creosote tests in the standard might invite product liability suits. There have been very few woodstove product liability suits, and UL has never been named in one. However, given that creosote is the second leading cause of woodstove-related fires, that situation would likely change if UL 1482 treated creosote as a product problem. Setting an acceptable limit on creosote would also be difficult to justify, but no more difficult than the educated guesses behind many provisions in UL standards. Unlike other provisions, however, it would arouse strong opposition from some manufacturers. A UL engineer, implicitly acknowledging that these considerations outweigh any technical concerns, allowed that UL would test for creosote "if industry came to us and asked for a test and would pay for it." But that hasn't happened and isn't likely to.
The certification business for woodstoves, at least in 1979, when UL 1482 was formally adopted, was neither comprehensive nor consistent. The market for third-party certification was unusual in several respects. On the demand side, UL is often thought to have leverage over industry because the demand for its services is inelastic. In countless product areas, such as microwave ovens and television sets, everything on the market is UL-listed. Firms often need UL approval to meet requirements incorporated into law or contract. This puts UL in a position to demand various safety measures. However, in the mid 1970s there were only scattered local requirements that woodstoves be listed "by a nationally recognized testing laboratory," and the demand for certification was correspondingly weak. No more than 10 to 25 percent of the woodstoves were certified by independent labs.
On the supply side, UL is often in a monopoly position. This allows UL to invest in standards-related research without the concern that other labs will capitalize on the effort. With woodstoves, however, there
has always been considerable competition from small testing labs. A CPSC survey conducted in 1981 concluded that UL had only 28 percent of the market. The competitors use UL 1482 as the standard for certification, but, as mentioned earlier, studies by the National Bureau of Standards confirm that actual test methods vary and some labs are far less demanding than others in judging woodstoves.
The government played no role regulating woodstoves; that is, until a man in Midland, Michigan, wrote a letter to his congressman.