UL 1482: Room Heaters, Solid-Fuel Type
At first blush, UL's standard for coal and wood-burning stoves appears complicated and highly technical. The current version, incorporating
minor changes made four years after the first edition was published in 1979, is sixty-one pages long and covers both the construction and performance of stoves. Some provisions specify design requirements. For example, cast-iron stoves must not be thinner than 3.17mm (one-eighth of an inch). Other provisions involve mechanical tests. The "strength test" for chimney connectors calls for a twenty-pound sandbag to be swung on a pendulum against the chimney connector. The stove itself is subject to various stability tests, including a "drop test" in which the stove is dropped ten times from a height of one inch. Other provisions are more general and subjective, such as the prohibition against "edges, corners, or projections that present a risk of a cut or puncture-type injury to persons." Twenty-six pages of UL 1482 are devoted to electrical blowers, an optional item not included on many stoves, which help circulate heat throughout the room. Given UL's orientation toward electrical devices, this section is extremely detailed and refers to many other UL standards for motors, wire, switches, and component parts.
But the fire tests are the guts of UL 1482. They subject the stove to both intense "flash fire" conditions and more stable, long-term burning conditions. The temperature at designated points on the stove's surface and surrounding walls must stay within specified tolerances during three separate tests. The manufacturer specifies the distance the stove should be from the wall during testing. If the stove passes, the subsequent label indicates the precise certified clearance (or "distance to combustibles").
From Proposal to Publication
There are two versions of the making of UL 1482: official and unofficial. Like textbook descriptions of the legislative process, the official version misses most of the important subtleties. But it describes the framework within which the standard was written and is necessary to understanding the unofficial story that follows, which is based more on interviews than on official documents.
The official story begins in January 1978, when UL "proposed" the standard to its Fire Council and to manufacturers of wood-burning appliances, circulating the standard for written comments. Five engineering councils composed of outside safety experts provide input to UL engineers in standards development. Council members may not have any formal relationship with manufacturers or distributors. Councils
meet only every other year, however, so most business is conducted by letter ballot. The standard was revised and circulated for comments in August. Three months later, UL hosted a two-day meeting for stove manufacturers and trade association representatives to discuss the proposed standard with UL's engineers. Based on comments received at those meetings, another revised version of the standard was circulated for comments in January 1979. By this time, the wording of the warning label was the only provision at issue. A revised warning label proposed by UL in April 1979 received sufficient support from industry for UL to consider the standard acceptable and publish it.
Successive drafts of the proposed standard indicate how it changed during this process. Unfortunately, this paper trail reveals little about the motivation for these changes. And UL employees are reluctant to discuss the deliberations that go into a standard. Even the so-called rationale statements recently added to UL standards are often brief and general, providing little insight into the trade-offs and underlying issues.
In the case of UL 1482, most of the changes involved the finer points of test methods. For example, the proposed standard described the charcoal briquettes to be used in testing by reference to the product manufactured by the Kingsford Chemical Company. The revised version adopted a more generic approach, specifying the size, weight, and moisture content of acceptable briquettes. The aspects of the standard that were changed most significantly during this process and appear to have generated the most disagreement were the warning labels and installation instructions. As originally proposed, UL 1482 required limited installation instructions and a warning label—or "caution mark," in UL terminology—on the stove. The Wood Energy Institute took strong objection to the warning label and convinced UL of Canada, but not UL, to drop the requirement. UL revised the labeling requirement, however, in response to this opposition. The minimum letter size for the warning label was reduced and, for stoves with glass doors, the label did not have to appear on the front of the stove. The requirements concerning installation instructions were less controversial. They were expanded during the revision process without substantial opposition.
Canvassing for Consensus
Once satisfied that industry representatives had no major objections to the standard, UL began a separate process to obtain acceptance from the American National Standards Institute that UL 1482 was a "na-
tionally recognized consensus standard." ANSI aims to be a central clearinghouse and general overseer of nongovernment standards-writers. However, the organization has limited resources, no technical staff, and no information collection system. It depends on the voluntary cooperation of standards-writers. Although UL routinely submits its published standards to ANSI for such approval, the gesture is largely a matter of courtesy without any practical significance for the recognition or use of UL standards.
There are three separate procedures for gaining ANSI approval. UL uses the one subject to the most criticism: the canvass process. Under this procedure, UL developed (and ANSI reviewed and approved) a "canvass list" of parties thought to be interested in reviewing the woodstove standard. A professor at Auburn University who had conducted research on woodstoves for the CPSC was the only individual on a list of twenty-six. The rest represented organizations ranging from the Alliance of American Insurers to UL's Consumer Advisory Council and the National Safety Council. The standard was distributed to those on the list with a request for comments and an affirmative or negative vote. ANSI also solicited "public review comments" through a notice in its newsletter, Standards Action .
Under ANSI's canvass method, public comments and a compilation of canvass votes are submitted to ANSI's Board of Standards Review (BSR), whose job is to certify "consensus." They do so mainly by examining any "unresolved negatives" that emerge from the process. In the terminology of the BSR, UL 1482 was a "clean case." It was submitted to ANSI with no "unresolved negatives." No comments were received from the general public during ANSI's own comment period. On the basis of that information, the BSR approved UL 1482 without discussion on January 28, 1981.
What appeared to be a "clean case" to the BSR was not nearly so straightforward for UL. The canvass process took UL over twenty months—longer than it took from official proposal to publication of the standard—and it generated numerous negative comments along the way. Negative ballots were cast (at least initially) by members of five organizations on the canvass list, including NFPA, the National Bureau of Standards, the International Conference of Building Officials (ICBO), and the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE). Others voted affirmatively but registered negative comments.
The objections were to the scope and severity of the standard. Rep-
resentatives from NFPA and NBS objected to the lack of any provisions concerning the tendency of stoves to produce creosote. Representatives from ICBO and ASHRAE objected to the stringency of various test methods. The former considered an aspect of the fire tests too weak, while the latter argued that the impact test for glazing was unreasonably stringent.
UL responded to each party that cast a negative vote, seeking to elicit a vote in favor. The Standards Department at UL is charged with this task. The department, with almost fifty employees, acts as an intermediary between commenters and UL engineers. The department aims to defuse opposition and gain acceptance for UL's standards by informing commenters of the reasons for the provision in question and, if this fails, by trying to convince them that improvements can be made in the future. Commenters often agree to vote in favor of a standard on the assurance of the Standards Department that the issue will be addressed in the future. This tactic changed all of the votes against UL 1482 but that of the International Conference of Building Officials. UL had to request a six-month extension from ANSI in order to bring ICBO around.
Several of the objections to UL 1482 were dismissed by UL in a rather perfunctory fashion. Those who objected to the lack of provisions governing creosote formation were told that ongoing research in the scientific community was expected to provide a data base upon which a future test method might be developed. This response appears less than forthright given the events preceding the canvass. There, in response to questions about how (and whether) to deal with creosote formation in chimneys, the matter was dropped because, according to UL's report of the meeting with industry representatives, "the discussion indicated that it was primarily an installation consideration and not a product construction or performance requirement for inclusion within the body of UL 1482." An internal UL memo dated March 19, 1985, indicates that UL is still "not in a position to include any creosote tests." And a UL engineer confirms that without a request and financial support from industry, there are no plans to develop such a test.
Other objections to UL 1482 were also "resolved" in an unresponsive manner. A building code official objected that the glazing impact test would "increase the cost of glass doors without producing a safer product." UL's response: the test was intended "to provide the assembly with impact conditions under various modes." UL offered no evidence that the product would actually be safer as a result.
The Unofficial Story and UL's Unpublished Standards
Missing from the official version of the adoption of UL 1482 are any details of what turns out to be the most critical step in the process: developing the "proposed" standard. Although the proposed standard was modified through UL's review and comment process, the changes were not significantly related to the safety implications of the standard. The most important provisions in UL 1482, at least from the point of view of safety, came from the original proposal and were not affected by the formal process that followed. The official story, then, picks up where the unofficial story ends—with the "proposed first edition" of UL 1482.
It is misleading to describe the standard circulated by UL in January 1978 as a "proposal." It was, in fact, both a proposal and a working (but unpublished) standard. UL had actually been certifying woodstoves for over twenty-five years when it circulated as a "proposal" the requirements it had been using. These provisions were contained in an unpublished UL standard (also referred to as a "desk standard"). Unpublished standards, the foundation of all UL standards, are not well known or understood. When the CPSC first began investigating woodstove safety, it operated for several months under the mistaken impression that there was no UL standard. In fact, there was an unpublished standard, just not a published one.
Unpublished standards and their method of development are one of the only blemishes on UL's otherwise excellent reputation. These standards are written entirely in-house by UL engineers and, true to their name, are not generally available to outsiders. Those who evaluate standards-writing by the extent to which the procedures are public and accessible are most critical of UL's unpublished standards. Leaving the merits of that debate aside until later, the fact is that unpublished standards are an integral part of UL and its standard for woodstoves. Relevant to the present discussion is how these standards take shape.
The Importance of Precedents
The process begins when a manufacturer of a product for which there is no UL standard asks UL to test and certify the product's safety. Lacking a standard with which to test the product, UL creates a rough draft (an unpublished standard), which is refined through use. Then, if there is sufficient demand, a formal "proposal" and publication follow.
Precedent is a guiding principle at UL, and it explains the direct origin of most provisions in UL 1482. The test method for the three fire tests, for example, came from UL's standard for fireplace stoves, UL 737. (Fireplace stoves are basically woodstoves without doors, and many of the provisions in UL 737 provided the basis for UL 1482.) Similarly, the provisions concerning metal thickness came from UL's standard for oil-burning appliances, according to a UL engineer in the Fire Department. That standard was also cited by UL as a precedent for the warning label eventually included in UL 1482.
Precedent says something about the source, but not the underlying rationale, of these provisions. The same question lurks behind each precedent: Where did the original provision come from? Take, for example, UL 737, which accounts for many provisions in UL 1482. Where did the provisions for UL 737 come from? Unfortunately, UL's own records do not document the complicated regulatory genealogy that covers ninety years, hundreds of published standards, and active testing in thousands of product categories. Even if it did, the original question would still remain: How does UL formulate requirements when there is no UL precedent? The answer seems to vary by type of requirement. Design requirements, performance standards, and labeling provisions seem to evolve differently. Like all UL standards, UL 1482 contains all three types of requirements. Deciding the appropriate combination of these approaches turns out to have safety implications as significant as the eventual content of each type of requirement.
Design Standards and Delegation
Design standards are disfavored by economists and standards purists, but not by UL engineers. Many of the requirements in UL 1482, and other UL standards, specify design parameters, such as the minimum metal thickness for cast-iron stoves. Economists favor performance standards—for example, a "burn through" test instead of a specific metal thickness—because such standards are less likely to constrain technological innovation. However, all of UL's design standards are qualified by an "equivalency statement" that, in theory, allows for technological innovation. This reads:
A product employing materials or having forms of construction differing from those detailed in the requirements of this Standard may be examined and tested in accordance with the intent of these requirements and, if found to be substantially equivalent, may be judged to comply with the Standard.
This clause is invoked "at least once a week," according to a UL attorney, who would not disclose any details about whether or when it has been applied to woodstoves (or any other specific product).
UL uses design standards for two reasons that are often overlooked in the discussion of performance and design standards. First, design standards are much cheaper from the point of view of testing. The thickness of cast iron can easily be measured. A performance test intended to simulate "burn through" would be much more complicated and expensive. Second, design standards—at least the way in which they are used by UL—allow certain matters to be "delegated" to the manufacturer. This is particularly helpful when field data or relevant research do not provide an adequate basis for a performance standard.
Many of UL's design standards are actually codifications of generally accepted business practice. The requirements for minimum metal thicknesses do not constrain woodstove manufacturers; they choose them in the first place. Design standards of this origin appear to contradict the notion that UL's standards are an "independent" test of safety. In UL's defense, reliance on industry practice, if done critically and selectively, helps keep down the cost of testing, while ensuring that products beneath the accepted minimum are not certified.
Performance Requirements and Educated Guesses
The design requirements in UL 1482 are not the most important from the point of view of safety; the performance requirements are. The fire tests, for example, specify that during testing the stove must not cause temperatures on exposed walls to rise more than 117° F above ambient temperature. Similarly, "a chimney connector furnished as part of the assembly shall not break, disassemble, or become damaged to the extent that it is unacceptable for further use after being subjected to a longitudinal force of 100 pounds." Unlike design specifications, which often leave the decisionmaking to industry, performance requirements are created entirely by UL's engineers. UL decides which aspects of performance to test and how to go about doing so.
On the first score, UL 1482 is quite comprehensive. It tests several aspects of normal stove operation as well as performance following various mishaps (for example, a heavy impact to the chimney connector). On the other hand, 1482 is far from scientific. According to UL, "sound engineering principles, research, records of tests and field experience … [and] information obtained from manufacturers, users, and
others having special experience" form the basis for its standard. Most test methods in UL 1482 reflect two factors not included in this list: educated guesses and concessions to the practicalities of product testing.
Guesswork abounds in UL's standards, although it is usually disguised by the exactitudes of scientific language. For woodstoves with glass doors, for example, the impact test for glazing calls for a steel sphere of 1.18 pounds mass and 50.8mm diameter to be dropped against the glass from a pendulum arc with a height of 16.25 inches. Research results certainly do not form the basis for this test. The explanation provided by a UL engineer is that a two-inch ball bearing—the steel sphere described more "scientifically" above—swung from around 45 degrees "seemed about right." The idea, according to this engineer, was to simulate an accidental jab against the glass with a fireplace poker. A larger ball would, of course, simulate a more serious jab. But absent any information on real-world experience with jabs and related mishaps, this educated guess lives up mainly to the second half of its name. A representative of a major glass manufacturer takes exception to UL's explanation. "We could never get [UL] to tell us why [the falling ball test] has these specific requirements." This engineer believes that the requirements came from some other UL standards. In fact, rather than simulating a specific hazard for woodstoves, the two-inch ball bearing test would more accurately be described as UL's generic impact test. It appears in similar form in a host of product standards, including the standard for portable video recording systems.
Even the most basic requirement of the three fire tests—that the temperature not rise more than 117° F on exposed surfaces and 90° F on unexposed ones —is largely guesswork. "There is some evidence to support these temperatures," observes a widely respected woodstove expert, but "they are still doubtful. Lots of different temperatures are plausible." A challenge to the rationale for these specific temperature tolerances was raised in the canvass process, but UL was unable to provide a specific response.
The practical necessities attendant to laboratory product testing help explain why guesswork often takes the place of science. In writing performance requirements, UL's engineers are sensitive to the cost of the endeavor. UL will not undertake costly scientific experiments where guesswork seems satisfactory. The engineers also try to keep the cost of the test itself within reasonable limits. For example, in UL 1482 a photoelectric method for measuring wisps of smoke was abandoned in
favor of less accurate visual observation tests because the former was considered too costly. Similarly, since walls and ceilings are made of a variety of materials, the most realistic test method would include separate tests for each material. Striking a balance that favors economy over realism, the tests are done with only one building material.
Product Certification and the Real World
The business of product testing also requires that test methods be reproducible. For example, myriad factors other than the woodstove itself affect the extent to which temperatures on surrounding walls will increase when the stove is used at a specified distance. The type of fuel, the type of chimney, the insulation in the room, not to mention the finer points of product testing (for example, type and placement of thermocouples), are all significant. A test method must control these influences sufficiently to ensure that the same test will yield similar results over time. Unfortunately, the more "controlled" the test, the less likely it is to bear a relationship to reality.
This is a recurring problem in product testing. The more inexpensive and reproducible the test, the more tenuous its relationship to what happens to the product in the real world. Performance standards require that numerous assumptions be made about how the product will be used in the real world. These assumptions can take many forms. Different sections of UL 1482 appear to be based on different notions of the relationship between test methods and reality. In some sections, UL takes its lead from the NFPA standards for chimneys and venting. The stove is tested, in other words, on the assumption that it will be installed in the method recommended by the NFPA. This assumption is on the utopian side of optimistic. An NBS engineer recounts that when the Bureau contracted to have a regulation NFPA 211 masonry chimney built for testing purposes, the mason exclaimed that the chimney was unusually sturdy. "We never build them like this," he told the engineer.
A particularly difficult question for UL is to what extent it should "test for" consumer misuse. Or, as a UL engineer puts it, "How forgiving should products be?" The answer implicit in UL 1482 is mixed. Several of the tests for structural integrity in 1482 simulate what might be considered average mishaps (for example, bumping the stove door or chimney connector). Other portions come much closer to simulating "worst case" conditions. The flash fire test, for example, is supposed to simulate the kind of overfiring that would occur if, say, a Christmas tree
or cardboard box were burned in the stove. The fire used in this test burns unusually hot and much longer than in a typical overfiring situation. Chimney height affects, among other things, the tendency of the stove to emit sparks into the room. The chimney used in all fire tests simulates a kind of worst condition. According to an NBS engineer, the chimney specified by UL has an unusual propensity to emit sparks. (This is not necessarily why UL chose the chimney, however, and neither is this particular chimney required if the manufacturer specifies otherwise.)
The portions of UL 1482 that are most controversial are those in which real-world experience diverges most from testing conditions. UL generally assumes that consumers are literate, obedient, and only occasionally clumsy. Most of the test methods in UL 1482 presume that the user will follow the manufacturer's instructions. Therefore, if the manufacturer's instructions say that a grate should not be placed inside the stove, UL tests without a grate. Since the use of grates is widespread and results in higher burning temperatures, an engineer with the International Conference of Building Officials thinks that "if a conventional grate [can] be placed in a heater, then it should be tested with one." UL disagrees.
This difference in testing philosophy explains why Consumer's Union (CU), publisher of Consumer Reports, graded down a stove that UL considered acceptable. CU considered the stove dangerous because of its tendency to emit sparks through the air inlets. UL, which tests stoves in accordance with NFPA's installation instructions—including, among other things, use of a floor protector—does not recognize the problem as a legitimate testing concern. That stove poses no danger—assuming it is used with a floor protector.
Evaluating UL 1482
Assessing the quality of UL 1482 as a safety standard is difficult because information about actual fires is limited and there may be significant variations in how the standard is applied. How test results are evaluated may also vary by laboratory. UL 1482 leaves many decisions to the discretion of the testing laboratory. Differences in test methods might allow a woodstove to pass the fire test at, say, twenty-eight inches at one lab and thirty-six inches at another. But since the UL standard itself is based on a combination of educated guesses, an agreed-upon margin of safety, and limited test data, it is likely that stoves certified for thirty-six inches would actually be safe at closer distances. In other
product areas, test data have frequently revealed that UL standards contain large, some say too large, margins of safety. Moreover, manufacturers often build in a margin of safety (actually, a margin of error) when they have their stoves tested. On the basis of stove design alone, engineers cannot calculate the distance at which the stove will pass the UL tests. Therefore, the manufacturer, who specifies the distance at which the stove is to be tested, must estimate the clearance, knowing that an overly optimistic estimate will result in expensive retesting. Accordingly, a stove certified for thirty-six inches might pass the test at a closer distance. In short, differences in product testing might lead to inconsistent applications of UL 1482, but the inconsistencies do not seem very important. As an NBS engineer put it, "The standard could be tightened up a great deal, but I don't think that it would make much difference in safety."
Several government studies of fire incident data have attempted, with mixed success, to quantify the nature and extent of fire damage related to woodstoves. All of these studies support the proposition that the consumer is responsible in one way or another—usually by improper installation or maintenance—for almost all such fires. A UL spokesman cites this as evidence that the standard is effective. While the conventional wisdom appears to hold true in a numerical sense—most studies blame the woodstove itself for only a few percent of all woodstove-related fires—it is not necessarily true in a policy sense. Even if the universe of injuries preventable by product improvements is small, it might still be easier to eliminate some of those injuries than to achieve a similar reduction in fires caused by consumer behavior. Moreover, some of the injuries "caused" by consumers could nevertheless be prevented by changes in the product.
Unfortunately, it is impossible to ascertain from recent studies of fire incident data whether certified stoves are actually any safer than uncertified ones. The data are both too general and unreliable. According to an NBS engineer, "Fire incident reports are sometimes detailed enough to indicate whether the fire originated in the appliance or the chimney, but they almost never indicate the appliance type or how far it was from the wall." None of the existing data bases even differentiates certified from uncertified stoves.
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.