The opinion of the court was delivered by: Justice Freeman
 Docket No. 94748-Agenda 23-September 2003.
 Plaintiff, Christy Adams, as special administrator of the estate of Janice Adams, brought a wrongful-death action in the circuit court of Cook County against Northern Illinois Gas Company (NI-Gas). The circuit court granted NI-Gas' motion for summary judgment. The appellate court reversed the grant of summary judgment in favor of NI-Gas and remanded the cause for further proceedings. 333 Ill. App. 3d 215. We allowed NI-Gas' petition for leave to appeal (177 Ill. 2d R. 315(a)), and now affirm the appellate court.
 The record contains the following pertinent evidence. Since 1971, Janice Adams (decedent) resided in a house located at 1294 Greenbay Avenue in Calumet City. Decedent's mother, Lucia Georgevich, bought the house, but decedent paid the mortgage and the utilities. Various appliances in the house, including a range, were fueled by natural gas.
 On the evening of December 7, 1995, decedent arrived home, opened a door, and stepped inside. The house exploded and was engulfed in flames, causing her death.
 First at the scene was the Calumet City fire department. Assistant chief Dan Smits and fire investigator Joe Ratkovich investigated the cause and origin of the explosion. Smits saw the fire and saw that the walls of the house had been blown out. He observed the body of decedent just inside what had been an entrance to the house. Smits inspected the gas meter, gas piping, and gas appliances and directed that all those items be removed and preserved.
 The Calumet City fire department determined that the cause of the explosion and fire was the failure of the flexible brass gas connector that connected the kitchen range to the gas supply. The brand name of the connector was "Cobra." Failure of the connector permitted a large amount of natural gas to escape and accumulate in the house. When decedent entered the house and turned on an electric light, a small spark from the switch ignited the gas. The Illinois State Fire Marshall, the United States Bureau of Alcohol, Tobacco and Firearms, and the private fire investigator employed by the homeowner's insurance carrier also investigated the explosion and all agreed that it was caused by the failure of the gas connector to the range.
 Plaintiff, one of decedent's daughters, brought a wrongful-death action in a two-count, first amended complaint. Count II named NI-Gas as a defendant. *fn1 Plaintiff alleged that NI-Gas "knew that Cobra brand natural gas appliance connectors were defective and prone to failure resulting in natural gas leaks and explosions." Plaintiff alleged that NI-Gas "had a duty to warn its customers, including plaintiff's decedent, about the existence of Cobra brand natural gas appliance connectors and the dangers of natural gas leak, explosion and fire associated with these connectors." Plaintiff alleged that NI-Gas breached this duty to warn in that NI-Gas: failed to provide (a) any or (b) adequate warning; (c) used an ineffective means to inform customers; (d) failed to initiate an inspection program to identify and remove Cobra brand natural gas appliance connectors from customer homes and businesses; and (e) failed to properly inspect decedent's home "to cause the removal of the aforesaid Cobra brand connector."
 The record includes the depositions of several opinion witnesses, including Charles Lamar, Wayne Genck, Norman Breyer, and Edward Karnes. Their testimony adduced the following additional evidence.
 The connector in this case was manufactured by the Cobra Hose Company, which has been out of business since 1979. Made as early as 1953, Cobra connectors were widely used in Illinois and other states. The Cobra connector essentially was a corrugated flexible brass tube with threaded brass connectors at each end that connect a gas appliance to the hard pipe gas source. The threaded connectors were telescoped and fastened to the ends of the corrugated brass tube by a process known as brazing. The compound used in the brazing process is composed of phosphorized brazing alloys containing a substantial portion of phosphorous and a high percentage of copper.
 It is undisputed that natural gas, in its original state, is odorless. The chemical ethyl mercaptan, which is a sulfur component, is added as an odorant to give natural gas its distinctive smell. In addition to sulfur that is intentionally added, natural gas itself produces sulfur compounds through intrinsic chemical reactions. By law, NI-Gas is required to supply odorized gas to its customers as a safety precaution, so that customers more easily can detect a gas leak. The natural gas that NI-Gas supplied to decedent was as the law required it to be.
 However, when sulfur is added to natural gas, as in the present case, a chemical reaction begins to occur between the phosphorous brazing alloy and the sulfur. This chemical reaction causes the brazed joint to corrode and deteriorate. Over time, the deterioration of the brazed joint results in its separation from the corrugated tube and the consequent release of natural gas into the home. Even the naturally occurring sulfides in the gas are sufficient to cause the brazed connector eventually to fail.
 In 1968, the American National Standards Institute (ANSI) *fn2 revised its standards on gas connectors and banned phosphorous brazing. ANSI's Z21 subcommittee on connectors is the committee that has jurisdiction over all domestic standards for natural gas ranges, furnaces, water heaters, and connectors. The Z21 specifications were modified to warn that the use of brazing compounds that contain phosphorous can result in a brittle joint and can be deadly.
 The record contains evidence that NI-Gas was aware of the potential danger in homes using Cobra connectors. In May 1976, NI-Gas' supervisor of Research Services reported to the Z21 subcommittee that the "sudden, mysterious separation of brass connectors and their brazed-on end fittings has been a concern of gas utility people for several years." In a letter dated December 14, 1979, the United States Consumer Product Safety Commission informed the American Gas Association (AGA) that Cobra connectors allegedly caused a number of fires in homes. According to the letter, while some jurisdictions did not allow the installation of Cobra connectors, many such connectors "may still be in service, and therefore may be susceptible to creating a significant hazard to the occupants of those residences equipped with such connectors." On December 19, the president of the AGA sent a letter to all its member companies, including NI-Gas, stating that the Commission had notified AGA that Cobra connectors had an increasing potential to fail over time.
 The record also includes copies of "Consumer News" notices that NI-Gas sent to its customers. The August/September 1978, June/July 1980, summer/fall 1981, and December 1981 notices indicated that an old connector could crack, creating an unsafe condition, when the appliance was moved. The December 1981, January 1985, May 1986, and June 1987 notices warned: "The U.S. Consumer Product Safety Commission has warned that certain appliance connectors manufactured prior to 1968 may be unsafe. If you are concerned, do not try to move the appliance to inspect the connector. Instead, call a qualified service agency of NI-Gas to make the inspection."
 Also, NI-Gas knew that failed Cobra connectors were determined to have caused many explosions and fires within its service area, including Aurora, Evanston, and Rockford. In the 1970s there were a series of fires in the Village of South Holland associated with brazed connectors. Wayne Kortum, a volunteer firefighter in South Holland and a NI-Gas employee, informed NI-Gas supervisors at the Glenwood district office, the district that includes the decedent's home, about the connectors involved with these fires. Thereafter, Kortum attended a general meeting at the Glenwood office where NI-Gas supervisors informed him and other service employees that there were problems with brazed connectors and that the service employees should look for these connectors in customers' homes.
 In November 1984, NI-Gas representatives participated in a meeting with officials from the Village of Skokie. The Skokie fire department had determined that several fires and an explosion in the Village were related to brazed connector failures. Carol Anderson, one of the NI-Gas attendees, testified that in the 1980s she was aware that brazed connectors were a hazard. According to John Agosti, a Skokie fire official, NI-Gas represented that it would notify its service and construction personnel about replacing brazed connectors. In turn, these employees would warn the NI-Gas customers with whom they came in contact.
 Charles Henry, a trained NI-Gas serviceman, testified in a deposition as follows. NI-Gas instructed its service employees on the potential danger of Cobra connectors. When a NI-Gas employee encountered a brazed connector, the employee was required to tag the connector and advise the customer that the connector needed to be replaced as soon as possible.
 Decedent's ex-husband, Leonard Adams, testified in a deposition as follows. He had observed NI-Gas employees read the gas meter in the utility room of decedent's home on occasion, but they did not examine anything in the house other than the meter. In 1978 or 1980, after having a new clothes drier installed by the appliance retailer, a gas leak was detected. Decedent telephoned NI-Gas. A NI-Gas employee came to the house and checked the gas pipe between the meter and the clothes drier. The employee discovered that the pipe was leaking and tightened it; he did not do anything else.
 NI-Gas moved for summary judgment against plaintiff. NI-Gas contended that it did not owe decedent a legal duty to warn her that her Cobra connector was potentially hazardous because decedent owned the connector and not NI-Gas. The circuit court granted NI-Gas' motion for summary judgment against plaintiff. *fn3
 Plaintiff appealed. Initially, the appellate court, with one justice dissenting, affirmed the grant of summary judgment in favor of NI-Gas, holding that NI-Gas did not owe decedent a legal duty. However, the appellate court modified its opinion upon denial of plaintiff's petition for rehearing. In its modified opinion, the appellate court, inter alia, reversed the grant of summary judgment in favor of NI-Gas. The appellate court held, "as a matter of law, that a utility company that has actual knowledge of a dangerous condition associated with the use of its product has a responsibility to its customers to warn them of that danger." 333 Ill. App. 3d at 224.
 This court allowed NI-Gas' petition for leave to appeal. 177 Ill. 2d R. 315(a). We subsequently granted the People's Gas Light and Coke Company et al. leave to submit an amicus curiae brief in support of NI-Gas. See 155 Ill. 2d R. 345.
 This matter is before us on the grant of summary judgment in favor of NI-Gas. The purpose of summary judgment is not to try a question of fact, but rather to determine whether a genuine issue of material fact exists. Happel v. Wal-Mart Stores, Inc., 199 Ill. 2d 179, 186 (2002); Gilbert v. Sycamore Municipal Hospital, 156 Ill. 2d 511, 517 (1993). Summary judgment is appropriate only where "the pleadings, depositions, and admissions on file, together with the affidavits, if any, show that there is no genuine issue as to any material fact and that the moving party is entitled to a judgment as a matter of law." 735 ILCS 5/2-1005(c) (West 2002).
 In determining whether a genuine issue as to any material fact exists, a court must construe the pleadings, depositions, admissions, and affidavits strictly against the movant and liberally in favor of the opponent. A triable issue precluding summary judgment exists where the material facts are disputed, or where, the material facts being undisputed, reasonable persons might draw different inferences from the undisputed facts. The use of the summary judgment procedure is to be encouraged as an aid in the expeditious disposition of a lawsuit. However, it is a drastic means of disposing of litigation and, therefore, should be allowed only when the right of the moving party is clear and free from doubt. Gilbert, 156 Ill. 2d at 518 (and cases cited therein); accord Espinoza v. Elgin, Joliet & Eastern Ry. Co., 165 Ill. 2d 107, 113-14 (1995). In appeals from summary judgment rulings, review is de novo. Outboard Marine Corp. v. Liberty Mutual Insurance Co., 154 Ill. 2d 90, 102 (1992).
 Plaintiff alleged negligence on the part of NI-Gas. To prevail in an action for negligence, the plaintiff must establish that the defendant owed a duty of care, that the defendant breached that duty, and that the plaintiff incurred injuries proximately caused by the breach. Espinoza, 165 Ill. 2d at 114; Ward v. K mart Corp., 136 Ill. 2d 132, 140 (1990). The existence of a duty is a question of law for the court to decide; however, the issues of breach and proximate cause are factual matters for a jury to decide (Thompson v. County of Cook, 154 Ill. 2d 374, 382 (1993)), provided there is a genuine issue of material fact regarding those issues (Espinoza, 165 Ill. 2d at 114).
 In this case, the sole inquiry before us concerns the existence of a legal duty. Plaintiff asserts that NI-Gas owed decedent a duty to warn her that Cobra connectors were potentially hazardous. NI-Gas denies that it had such a duty because decedent owned the connector and not NI-Gas.
 There can be no recovery in tort for negligence unless the defendant has breached a duty owed to the plaintiff. Boyd v. Racine Currency Exchange, Inc., 56 Ill. 2d 95, 97 (1973); accord LaFever v. Kemlite Co., 185 Ill. 2d 380, 388 (1998). Duty is a question of whether the defendant and the plaintiff stood in such a relationship to one another that the law imposed upon the defendant an obligation of reasonable conduct for the benefit of the plaintiff. In determining whether a duty exists, a court looks to certain relevant factors, including: (1) the reasonable forseeability that the defendant's conduct may injure another, (2) the likelihood of an injury occurring, (3) the magnitude of the burden of guarding against such injury, and (4) the consequences of placing that burden on the defendant. Happel, 199 Ill. 2d at 186-87; Ward, 136 Ill. 2d at 140-41; Kirk v. Michael Reese Hospital & Medical Center, 117 Ill. 2d 507, 526 (1987). In support of their respective positions, the parties invoke two sources of law: (1) the common law, and (2) NI-Gas' tariff on file with the Illinois Commerce Commission.
 American consumers have been using gas as fuel for illumination or heat for over a century. Courts from across the nation, including Illinois courts, long ago considered the factors in determining the existence of a duty with respect to the duties that gas distributors owe to their customers concerning escaping gas. The common law, which is always heedful of realities when it formulates rules to govern conduct (Graham v. North Carolina Butane Gas Co., 231 N.C. 680, 684-85, 58 S.E.2d 757, 761 (1950)), has established the following principles.
 Gas is a dangerous substance or commodity when it is not under control. Metz v. Central Illinois Electric & Gas Co., 32 Ill. 2d 446, 450 (1965); McClure v. Hoopeston Gas & Electric Co., 303 Ill. 89, 97 (1922); accord Suiter v. Ohio Valley Gas Co., 10 Ohio St. 2d 77, 78, 225 N.E.2d 792, 793 (1967); Bellefuil v. Willmar Gas Co., 243 Minn. 123, 126, 66 N.W.2d 779, 782 (1954); Graham, 231 N.C. at 684, 58 S.E.2d at 761. However, a gas company is not liable as an insurer for injuries sustained as the result of the escape of gas. Rather, the company is liable for its negligence in permitting the gas to escape. Pappas v. Peoples Gas Light & Coke Co., 350 Ill. App. 541, 548 (1953); accord Bellefuil, 243 Minn. at 126, 66 N.W.2d at 782; Graham, 231 N.C. at 685, 58 S.E.2d at 761; 27A Am. Jur. 2d Energy & Power Sources §368, at 278 (1996); 38A C.J.S. Gas §119, at 143 (1996). Expressions of the degree of care that a gas company must exercise range from "reasonable" (see, e.g., Graham, 231 N.C. at 685, 58 S.E.2d at 761) to "high" (see, e.g., McClure, 303 Ill. at 97). This variety of expression simply means that a gas company must exercise a degree of care to prevent the escape of gas from its pipes commensurate with or proportional to the level of danger which it is the company's duty to avoid. Metz, 32 Ill. 2d at 450; Cosgrove v. Commonwealth Edison Co., 315 Ill. App. 3d 651, 654-55 (2000); accord Lewis v. Vermont Gas Corp., 121 Vt. 168, 182, 151 A.2d 297, 306 (1959); Doxstater v. Northwest Cities Gas Co., 65 Idaho 814, 826-27, 154 P.2d 498, 504 (1944); Bellefuil, 243 Minn. at 126, 66 N.W.2d at 782; 27A Am. Jur. 2d Energy & Power Sources §373, at 281 (1996); 38A C.J.S. Gas §120, at 145-46 (1996); L. Tellier, Annotation, Liability of Gas Co. for Injury or Damage Due to Defects in Service Lines on Consumer's Premises, 26 A.L.R.2d 136, 146 (1952).
 While a gas company must exercise the requisite degree of care so that no injury occurs in the distribution of gas while it is under the company's control, such responsibility is limited to the time the gas is in the company's own pipes. Doxstater, 65 Idaho at 827, 154 P.2d at 504 (collecting cases). In Illinois, the seminal example of the common law rule pertaining to gas distribution in a consumer's pipes and fixtures is Clare v. Bond County Gas Co., 356 Ill. 241 (1934).
 In Clare, the plaintiff opened a shop and hired a plumber to install a gas stove for heat. After the installation, she noticed an offensive odor that irritated her eyes and gave her a headache. She notified the gas company. The president of the gas company visited the shop several times and made suggestions to remedy the situation. His suggestions were followed, but the problem continued. The smell was so strong in the closet where the gas meter was located that the plaintiff kept the door to the closet closed. Several weeks after the unsuccessful attempts to locate the source of the problem, a friend of the plaintiff was looking for a screwdriver. He lit a match to help him look for it in the dark closet. He opened the closet door and an explosion occurred. It was subsequently discovered that the gas pipe that ran beneath the floor contained holes caused by rust. The gas that escaped from the pipe had accumulated in the closet. Clare, 356 Ill. at 241-43. Appealing a judgment in favor of plaintiff, the gas company contended that "there was no evidence in the record to warrant the finding that it [the gas company] had notice and knowledge that the pipes were leaking and gas was escaping into the building; that without such notice or knowledge there was no duty incumbent upon it to shut off the gas supply." Clare, 356 Ill. at 243.
 Reversing the judgment in favor of plaintiff, Clare relied on established common law: "In the absence of notice of defects it is not incumbent upon a gas company to exercise reasonable care to ascertain whether or not service pipes under the control of the property owner or the consumer are fit for the furnishing of gas." Clare, 356 Ill. at 244. Where a gas company does not install the pipes or fixtures on a customer's premises, and does not own them and has no control over them, the company is not responsible for their condition or for their maintenance, and as a result is not liable for injuries caused by a leak therein of which the company had no knowledge. Clare, 356 Ill. at 244 (collecting cases). Clare looked to the common law as evolved up to that time and today continues to accord with our understanding of the common law rule. Accord Oliver v. Peoples Gas Light & Coke Co., 5 Ill. App. 3d 1093, 1099 (1972); accord Bellefuil, 243 Minn. at 126, 66 N.W.2d at 782 (discussing rule in context of gas appliances); Doxstater, 65 Idaho at 827-28, 154 P.2d at 504, quoting Kelley v. Public Service Co. of Northern Illinois, 300 Ill. App. 354, 362 (1939); 27A Am. Jur. 2d Energy & Power Sources §§394, 395 (1996) (stating rule in context of appliances); 27A Am. Jur. 2d Energy & Power Sources §403 (1996) (stating general rule); 38A C.J.S. Gas §123, at 151-53 (1996); 26 A.L.R.2d at 156.
 Courts reason that a person's duty can extend no further than the person's right, power, and authority to implement it. Gas company employees do not have the right to enter the premises of their customers to inspect pipes or fixtures except upon the license or permission of the owner. Clare, 356 Ill. at 244. The consumer, by application for gas service, assumes the burden of inspecting and maintaining the pipes and fittings on the consumer's property in a manner reasonably suited to meet the required service. The company has the right to assume that the customer's interior system of pipes and fittings is sufficiently secure to permit the gas to be introduced with safety. Clare, 356 Ill. at 244-45 (collecting cases); accord Bellefuil, 243 Minn. at 126-27, 66 N.W.2d at 782-83; Graham, 231 N.C. at 685, 58 S.E.2d at 761; Moran Junior College v. Standard Oil Co. of California, 184 Wash. 543, 552, 52 P.2d 342, 346 (1935); 27A Am. Jur. 2d Energy & Power Sources §403 (1996).
 Courts also reason that, in a negligence action, knowledge of the facts out of which the duty to act arises is essential. In order that an act or omission may be regarded as negligent, the defendant must have knowledge, or ought to have known from the circumstances, that the allegedly negligent act or omission endangered another. Weber v. Interstate Light & Power Co., 268 Wis. 479, 482, 68 N.W.2d 39, 41 (1955). Accordingly, the common law rule of no duty of a gas company with respect to a consumer's pipes or fittings is premised on the gas company's lack of knowledge or notice of a gas leak. See, e.g., Clare, 356 Ill. at 244 (stating rule with proviso of gas company's lack of knowledge or notice); Bellefuil, 243 Minn. at 129, 66 N.W.2d at 784 ("the duty, by reason of actual or constructive notice of some dangerous condition, must arise before the gas company can be found negligent for its failure to inspect or shut off the gas supply").
 Considering the requirement of the gas company's knowledge or notice of a gas leak, the exception to the common law rule is evident:
"Where it appears that a gas company has knowledge that gas is
escaping in a building occupied by one of its consumers it becomes
the duty of the gas company to shut off the gas supply until the
necessary repairs have been made although the defective pipe or
apparatus does not belong to the company and is not in its charge
or custody." Clare, 356 Ill. at 243-44.
 Accord Graham, 231 N.C. at 685, 58 S.E.2d at 761-62 (citing Clare); 27A Am. Jur. 2d Energy & Power Sources §413, at 309-10 (1996); 38A C.J.S. Gas §123, at 153-54 (1996); 26 A.L.R.2d at 150. In the specific context of gas appliances, courts have gone so far as to impose on a gas company that has knowledge of a gas leak a duty to inspect:
"[W]henever a gas company is in possession of facts that would
suggest to a person of ordinary care and prudence that an
appliance of a customer is leaking or is otherwise unsafe for the
transportation of gas, the company has a duty to investigate, as a
person of ordinary care and prudence similarly situated and
handling such a dangerous substance would do, before it continues
to furnish additional gas. The duty to exercise reasonable
diligence to inspect or shut off the gas supply is measured by the
likelihood of injury. Circumstances may be such as to require a
gas company to investigate immediately and shut off the gas supply
until repairs are made. The nature of the notice may also affect
the extent of inspection necessary." Bellefuil, 243 Minn. at
128-29, 66 N.W.2d at 783-84.
 It is clear that the knowledge that would impose on a gas company this duty is not limited to actual knowledge, but may include constructive knowledge or notice. It is sufficient if the gas company received facts which would have made the defects known to an ordinary prudent person. For example, Clare was rendered in the context of the gas company's denial of "notice or knowledge." (Emphasis added.) Clare, 356 Ill. at 243. Further, this court expressly-and correctly-stated the common law rule with the accepted proviso of a gas company's lack of knowledge (Clare, 356 Ill. at 243 ("Where it appears that a gas company has knowledge")) or notice (Clare, 356 Ill. at 244 ("In the absence of notice")). See Mrdalj v. Public Service Co. of Northern Illinois, 308 Ill. App. 424, 430 (1941); Kelley, 300 Ill. App. at 362; Kilmer v. Browning, 806 S.W.2d 75, 83 (Mo. App. 1991); Ruberg v. Skelly Oil Co., 297 N.W.2d 746, 751 (Minn. 1980); Fore v. United Natural Gas Co., 436 Pa. 499, 504-05, 261 A.2d 316, 318-19 (1970); Bellefuil, 243 Minn. at 128-29, 66 N.W.2d at 783-84.
 Further, Clare was directed not only to actual gas leaks, but also to defects. Clare, 356 Ill. at 244 ("In the absence of notice of defects" (emphasis added)). "The rule in Illinois as to the liability of a gas company is such company is responsible for a customer's pipe if it has knowledge of a leak or of a possible defect therein." (Emphasis added.) Oliver, 5 Ill. App. 3d at 1099; accord Bellefuil, 243 Minn. at 128-29, 66 N.W.2d at 783-84 (speaking of a customer's gas appliance that "is leaking or is otherwise unsafe for the transportation of gas" (emphasis added)); 27A Am. Jur. 2d Energy & Power Sources §413, at 310 (1996) (stating "that if a gas company has notice of a leak or defect in pipes or lines owned or controlled by a consumer, it is under a duty to notify the consumer and see that the leak or defect is repaired, or shut off the gas").
 This common law rule and corresponding exception serve the concept that a gas company is not an insurer for any injury sustained as a result of escaping gas, but rather is liable only for its negligence. "To apply any other rule would make the gas supplier an insurer if anything went wrong with any of the appliances over which it had no control." Wilson v. Home Gas Co., 267 Minn. 162, 172, 125 N.W.2d 725, 732 (1964).
 As the appellate court in this case recognized, Illinois courts have not addressed a gas company's duty to warn its customers of the possible deterioration of the customer's fixtures when they are damaged, in part, due to the gas product itself. 333 Ill. App. 3d at 220. However, addressing the same facts as in this case, two decisions from other jurisdictions recognize that gas companies who have notice of the danger caused by sulfides in their gas coming in contact with brazed connectors owe common law tort duties: Lemke v. Metropolitan Utilities District, 243 Neb. 633, 502 N.W.2d 80 (1993), and Halliburton v. Public Service Co. of Colorado, 804 P.2d 213 (Colo. App. 1990). We agree with the appellate court that these cases are instructive. 333 Ill. App. 3d at 220-22.
 In Lemke, a gas explosion destroyed the home of Lorraine and Kenneth Lemke and severely injured Lorraine. Lemke, 243 Neb. at 634-37, 502 N.W.2d at 82-84. The trial court found that the cause of the explosion was a Cobra connector, which failed due to the interaction of the phosphorous brazing alloy and the gas. Although there was evidence that the Metropolitan Utilities District (MUD) installed thousands of Cobra connectors in the homes of MUD customers, there was no evidence that MUD installed the Cobra connector to the plaintiff's gas range. The court entered judgment in favor of plaintiffs. Lemke, 243 Neb. at 642, 502 N.W.2d at 86.
 Appealing from the judgment, MUD contended "that it had no duty to notify its customers concerning a potential hazard from Cobra connectors, especially a customer who may not have purchased the connector from MUD." Lemke, 243 Neb. at 648, 502 N.W.2d at 90. The Nebraska Supreme Court rejected this contention.
 The Lemke court reviewed its past statements of the earlier-discussed common law principles. The court concluded:
"Because a gas company has a non-delegable duty to exercise due
care regarding natural gas supplied to a customer, a gas company's
duty of care not only pertains to the company's distribution of
gas through its pipelines, but extends to distribution through a
customer's service line or gas appliance that the company knows,
or should know, is unsafe for conducting or using gas." Lemke, 243
Neb. at 651, 502 N.W.2d at 91.
 The court noted, as the record in this case shows, that the American Gas Association warned all of its members, including MUD, that Cobra connectors presented a danger in the distribution of natural gas. The court reasoned:
"When MUD received information about the dangerous condition or
potential hazard involving Cobra connectors but did not
disseminate this critical information to its customers who were
using gas appliances with Cobra connectors, MUD effectively
exerted control in a situation that could eventually culminate in
injury to customers who continued to use gas supplied by MUD."
Lemke, 243 Neb. at 648, 502 N.W.2d at 89.
 According to the court, that information
"placed MUD on notice that its customers who had gas appliances
with Cobra connectors would be endangered when the connector
separated from a gas service line or appliance. Consequently, when
MUD became aware that the distribution of gas through a Cobra
connector presented a risk of injury to customers, MUD had the
duty to use due care, such as issuance of a warning, to protect
customers ***." Lemke, 243 Neb. at 652, 502 N.W.2d at 92.
 As in Lemke, NI-Gas' superior knowledge of the risks pertaining to Cobra connectors begat a duty of due care, such as issuing a warning to its customers.
 In Halliburton, the Public Service Company of Colorado, similar to NI-Gas here, knew at least since the 1970s that a large number of brazed connectors failed because of the interaction of the brazed connector and the sulfides in the gas. The court cited four reasons to impose a duty on the gas company to inspect plaintiff's brazed connector: (1) the relatively insignificant amount of time and expense that defendant would have expended to evaluate the connector and take corrective action; (2) two service calls at plaintiff's home after the gas company knew of this hazard, which affected approximately 45,000 homes in the Denver area; (3) the likelihood of the connector failing and possibly causing an explosion unless corrective action were taken; and (4) defendant's expertise in dealing with such problems. The court continued: "The most compelling reason, however, for imposing a ...