Bernard Dale Ferrell (plaintiff) filed a negligence action against J.W. Esparza, doingbusiness as Joe's Steam-It (Joe's), to recover damages for injuries he suffered as a result ofhis exposure to excessive levels of carbon monoxide. The circuit court of Saline Countyentered a summary judgment in favor of plaintiff on the issue of liability. The jury awarded$355,000 in damages to plaintiff. Joe's appeals. On appeal Joe's contends that the summaryjudgment was improper because Joe's owed no duty to plaintiff and its conduct was not aproximate cause of plaintiff's injuries.

The basic facts are not disputed. On December 27, 1991, plaintiff was employed byRoundy's, Inc. (Roundy's), and was assigned to work an afternoon shift in its Saline Countywarehouse. Food products were stored in this warehouse. When plaintiff reported to thewarehouse at approximately 3 p.m., he was directed to begin moving frozen-food productsout of a dairy cooler located inside the warehouse. The cooler was a room about 10 feetfrom floor to ceiling and about 12 feet wide. There were two entrances to the cooler. Plasticcurtain strips covered the entrances. The frozen inventory was to be removed so that thedairy cooler could be cleaned. Roundy's had been given 24 hours to clean the cooler, afteran inspection revealed an unsanitary condition inside.

Roundy's hired Joe's to steam-clean and to sanitize the cooler. The job was scheduledto be completed in 12 hours. Joe's employees, Ed Esparza and Doug Ewell, reported to thewarehouse at about 3 p.m. on December 27, 1991. When they arrived, Esparza and Ewellsaw Roundy's employees using forklift trucks to remove products from the cooler. Roundy'semployees continued to remove the inventory while Esparza and Ewell set up their steam-cleaning equipment. Esparza and Ewell placed the steam-cleaning machine inside thewarehouse but outside the cooler. The machine was stationed approximately 50 feet fromthe front door of the cooler. It was near a railroad dock door that had been partially openedso that there would be some air flow to prevent the machine from overheating. Roundy'swould not permit the railroad dock door to be opened completely because of its concern thatoutsiders would enter the building. Joe's steam-cleaning machine was powered by gasoline. Its heater ran on kerosene.

Both Esparza and Ewell were aware that the steam-cleaning machines producedcarbon monoxide. Both were aware that exposure to carbon monoxide was hazardous andpotentially fatal. Both knew the signs and symptoms of carbon monoxide poisoning. Joe'stold its employees that the steam-cleaning machines were not to be brought inside a building. Joe's instructed its employees to keep the steam-cleaning machines outside to allow forventilation and to prevent overheating. Joe's did not provide its employees with a carbonmonoxide detector to use during the steam-cleaning process. Ewell testified that he hadsteam-cleaned inside other buildings but that the steam-cleaning machine was kept outsideand long hoses were employed. He remembered working only one job where the machinewas actually brought inside. That was a 20- or 30-minute job.

Because of the unplanned delay in removing inventory from the cooler, Joe'semployees did not start cleaning until about 5 p.m. Esparza and Ewell began cleaning thefront walls of the cooler while Roundy's employees continued to remove products throughthe rear door. Three or four forklift trucks were moving in and out of the cooler as Esparzaand Ewell began to work. Soon after they started cleaning, Esparza and Ewell noticedclouds of steam condensation building, making it difficult to see inside the cooler. A fanwas placed in the front entrance to the cooler. It drew the steamy air from the cooler andblew it into the warehouse. There were two ventilation windows inside the cooler, but theywere not open. There was no cross-ventilation.

Because of the deadline it faced, Roundy's called in a second cleaning company. Thesecond company arrived sometime between 7 p.m. and 8 p.m. and began steam-cleaning therear part of the cooler. The second company used a large, gasoline-powered steam-cleaningmachine and two smaller electric machines. The larger machine was set up on a trailer bedon a dock inside the warehouse, near the rear door of the cooler. The two smaller machineswere set up inside the cooler. All of the machines had either kerosene- or diesel-poweredheaters.

Throughout the cleaning process, plaintiff and other Roundy's employees wereworking inside the cooler. They were using fuel-powered water vacuums and squeegees torid the cooler floor of water produced during the steam-cleaning process. They alsocontinued to move inventory around inside the cooler.

About six hours into the cleaning process, Esparza and Ewell noticed a haze in thecooler. During a break, they learned that some of Roundy's employees were complainingof headaches and nausea. Esparza also had a headache and felt nauseous. Esparza thoughtthat carbon monoxide emissions from the cleaning equipment caused the haze inside thecooler room, and he mentioned that to a Roundy's manager. He and Ewell then returned tothe cooler to finish cleaning it. They worked for another hour before leaving the building.

While working inside the cooler, plaintiff became dizzy. He felt sick to his stomachand his chest was tight. As he walked out of the cooler and into the warehouse, hecollapsed. A coworker noted plaintiff's condition and called for assistance. Plaintiff andanother coworker who had similar symptoms were transported to Ferrell Hospital.

Dr. Partridge, an emergency medicine specialist, was called to treat plaintiff and theother Roundy's employee. Dr. Partridge testified that both men presented with the samehistory. Both men had been working inside the cooler for an extended period of time. Afterworking several hours, each began to complain of a headache, nausea, weakness, andblurred vision. Dr. Partridge ordered blood tests. Plaintiff's blood test revealed a carbonmonoxide level of 26.7. Dr. Partridge testified that his initial diagnosis was mild-to-moderate carbon monoxide poisoning. He opined that the carbon monoxide level inplaintiff's blood probably peaked at 31. The normal level of carbon monoxide in the bloodis 2.7.

Plaintiff was admitted to the hospital and treated with pure oxygen. He wasdischarged the following morning, after blood tests revealed that his carbon monoxide levelhad returned to the normal range and that his vital signs were found to be within normallimits. Following his discharge, plaintiff suffered from symptoms of weakness, breathingdifficulties, dizziness and balancing problems, anxiety and jitters, angry outbursts, andconfusion.

Dr. Michael Evans, a toxicologist retained by plaintiff, testified that plaintiff'scondition was caused by an exposure to an excessive level of carbon monoxide. Heexplained that carbon monoxide binds to hemoglobin, depriving the blood of oxygen. Theprocess also renders the blood unable to transport carbon dioxide from the tissues back tothe lungs, resulting in a buildup of carbon dioxide in the tissues.

Joe's expert, Dr. Alan Weston, an environmental engineer, opined that the carbonmonoxide produced by Joe's machine alone would not have been sufficient to cause carbonmonoxide poisoning. He was not critical of Joe's employees for setting up the steam-cleaning machine inside the warehouse, indicating that because the warehouse was so large, it was almost like being outside. He concluded that emissions produced by Joe's machinewould have been diffused and disbursed throughout the warehouse, resulting in reducedconcentrations throughout the building. Dr. Weston conceded that the carbon monoxidelevels produced by Joe's steam-cleaning machine would have contributed to the carbonmonoxide level inside the cooler. He testified that the carbon monoxide produced by themachines sitting in the warehouse would have been distributed in equal concentrationsthroughout the cooler and the warehouse. Dr. Weston opined that there should have beensome device to measure carbon monoxide emissions inside the cooler because the machines inside the cooler were combusting fuel. Dr. Weston testified that he could not state theemissions concentrations of each machine used inside the warehouse because he did nothave sufficient information about the engine specifications of each machine.

Joe's contends that the trial court erred in granting a summary judgment in favor ofplaintiff. Joe's argues that it owed no duty to plaintiff and that its conduct was not aproximate cause of plaintiff's injury. In considering a motion for summary judgment, thetrial court's task is to determine whether a disputed question of fact exists. Block v. LohanAssociates, Inc., 269 Ill. App. 3d 745, 759, 645 N.E.2d 207, 217 (1993). A summaryjudgment is properly granted if the pleadings, depositions, admissions, and affidavits showthat there is no genuine issue of material fact and that the moving party is entitled to ajudgment as a matter of law. 735 ILCS 5/2-1005 (West 1994). The review of a summaryjudgment is de novo. Block, 269 Ill. App. 3d at 759, 645 N.E.2d at 217.

A duty of care arises when the parties stand in such a relationship to one another thatthe law imposes upon the defendant an obligation of reasonable conduct for the benefit ofthe plaintiff. Kirk v. Michael Reese Hospital & Medical Center, 117 Ill. 2d 507, 525, 513N.E.2d 387, 396 (1987). Stated differently, "[E]very person owes to all others a duty toexercise ordinary care to guard against injury which naturally flows as a reasonably probableand foreseeable consequence of his act, and[] such duty does not depend upon contract ***but extends to remote and unknown persons." Nelson v. Union Wire Rope Corp., 31 Ill. 2d69, 86, 199 N.E.2d 769, 779 (1964). Factors relevant in determining whether a duty existsand the scope of that duty include the foreseeability of injury, the likelihood of injury, themagnitude of the risk of injury, the burden of guarding against the injury, and theconsequences of placing that burden on the defendant. Unger v. Eichleay Corp., 244 Ill.App. 3d 445, 449, 614 N.E.2d 1241, 1244 (1993). The question of whether a duty existsand the scope or range of protection of such a duty are normally questions of law to bedetermined by the court on a case-by-case basis. Kirk, 117 Ill. 2d at 525, 513 N.E.2d at 396;Taake v. WHGK, Inc., 228 Ill. App. 3d 692, 712, 592 N.E.2d 1159, 1173 (1992).

In this case, Joe's was hired to steam-clean the dairy cooler inside the warehouse. Inperforming that work, Joe's employees were legally required to exercise the degree of carethat a reasonably prudent steam-cleaning company would exercise under the same or similarcircumstances. It is undisputed that Joe's knew that its cleaning equipment produced carbonmonoxide emissions. Joe's instructed its employees that the cleaning machines were not tobe set up inside. Joe's directed its employees that these machines were only to be operatedoutside, where the emissions could be quickly dissipated. Both Esparza and Ewell knew ofthe serious health hazards associated with exposure to excessive levels of carbon monoxideand the symptoms of carbon monoxide poisoning. It was clearly foreseeable that any workerwho was exposed to an excessive concentration of carbon monoxide in the cooler couldsuffer serious, if not fatal, injuries. See Hammer v. Slive, 27 Ill. App. 2d 196, 169 N.E.2d400, 402 (1960) (noting that the lethal effect of excessive carbon monoxide is a matter ofcommon knowledge).

The undisputed facts in this record show that there was a reasonable likelihood thatworkers who spent an extended period of time inside the cooler would be exposed todangerously high levels of carbon monoxide, that the probability that those exposed to thehazard would suffer serious or fatal injuries was considerable, and that, on balance, theburden of guarding against the hazard was modest. After considering the relevant factors,we conclude that Joe's owed a duty of care to plaintiff. Joe's had a duty to perform itssteam-cleaning operation in a manner that would not create a carbon monoxide hazard tothose in the work area. Joe's employees violated their employer's instructions by bringingthe machine indoors. The employees having done so, Joe's had a duty to ensure that therewas adequate ventilation in the work area during its cleaning operations, to assess the carbonmonoxide levels in the work area, and to warn those in the work area once it was discoveredthat the carbon monoxide levels in the work area were hazardous.

The record demonstrates that Joe's breached its duty to the plaintiff and other workersin the cooler. It is undisputed that Joe's employees operated the cleaning equipment insidethe warehouse despite instructions from their employer that the steam machines were not tobe brought inside. Joe's employees operated this equipment indoors without any carbonmonoxide detection devices. Joe's employees continued to operate the equipment eventhough they expressed concern about the lack of adequate ventilation within the warehouseand cooler. Joe's employees took no steps to assess the adequacy of the ventilation (a singlefan drawing air out of the cooler) after additional carbon-monoxide-producing machinerywas brought into the cooler. Joe's employees made no attempt to monitor the level of carbonmonoxide in the work area, nor did they make an attempt to have it monitored. Nor did theywarn those working inside after they recognized that the haze forming inside the cooler waslikely carbon monoxide. Instead, Joe's employees returned to the cooler and continued tooperate the steam-cleaning equipment even though they were experiencing symptoms ofcarbon monoxide poisoning. Given the undisputed facts, Joe's failure to act on a number ofoccasions constituted breaches of its duty of care to those who were working inside thecooler that evening.

Joe's is not relieved of its duty merely because the second cleaning company had andbreached the same duty or because the second company's machines contributed to the carbonmonoxide levels inside the cooler. Though neither cleaning company had any control overthe equipment and employees of the other or over Roundy's employees, each had a commonduty to use reasonable care in performing its cleaning operations. See Economy Light &Power Co. v. Hiller, 203 Ill. 518, 520-21, 68 N.E. 72, 73 (1903).

Finding that Joe's breached its duty to plaintiff does not resolve the liability issue, asthere must be a proximate causal connection between Joe's breach of duty and the damagesthat plaintiff suffered. See Stojkovich v. Monadnock Building, 281 Ill. App. 3d 733, 738,666 N.E.2d 704, 708 (1996). Joe's contends that its operation of the steam-cleaningequipment inside the warehouse was not a proximate cause of plaintiff's injury.

A proximate cause is one that produces an injury through a natural and continuoussequence of events unbroken by any effective intervening cause. Unger, 244 Ill. App. 3dat 451, 614 N.E.2d at 1246. According to fundamental principles of tort law, there may bemore than one proximate cause of an injury, and a defendant may be held liable for itsconduct whether it contributed in whole or in part to the plaintiff's injury, so long as thatconduct was a proximate cause of the injury. Nelson, 31 Ill. 2d at 88, 199 N.E.2d at 780. A tortfeasor cannot avoid responsibility merely because another person is guilty ofnegligence contributing to the same injury, even though the injury would not have occurredbut for the negligence of the other person. See St. Paul Insurance Co. of Illinois v. Estateof Venute, 275 Ill. App. 3d 432, 438, 656 N.E.2d 113, 118 (1995). Though proximate causeis ordinarily a question for the trier of fact, it becomes a question of law when the materialfacts are undisputed and there can be no difference in the judgment of reasonable personsas to the inferences to be drawn from them. Block, 269 Ill. App. 3d at 756, 645 N.E.2d at215.

Proximate cause is composed of two distinct concepts: cause in fact and legal cause. Lee v. Chicago Transit Authority, 152 Ill. 2d 432, 455, 605 N.E.2d 493, 502 (1992);Thacker v. UNR Industries, Inc., 151 Ill. 2d 343, 354, 603 N.E.2d 449, 455 (1992). Legalcause is essentially a question of foreseeability. Lee, 152 Ill. 2d at 456, 605 N.E.2d at 503. Earlier in this decision we concluded that it was foreseeable that workers could sufferserious injuries from carbon monoxide poisoning if they were working in an inadequatelyventilated area where machines were producing carbon monoxide emissions.

Cause in fact is established when there is a reasonable certainty that a defendant'sconduct caused the injury or damage claimed. Lee, 152 Ill. 2d at 455, 605 N.E.2d at 502. The defendant's conduct is said to be a cause of an event if it was a material element and asubstantial factor in bringing the event about. Thacker, 151 Ill. 2d at 354-55, 603 N.E.2dat 455.

In its brief and argument before this court, Joe's argued that there was "not one pieceof evidence" that carbon monoxide from its machine ever reached the cooler. However, thatargument ignores the fact that Joe's own expert conceded that carbon monoxide emissionsproduced by Joe's machine circulated throughout the warehouse, including the cooler.

Joe's also argued that the equipment of Roundy's and the other steam-cleaningcompany was the cause of the carbon monoxide in the cooler and that even if "traceamounts" of the carbon monoxide emitted from its machine had been introduced into thecooler and had "some effect" on plaintiff, such a "de minimis quantity" was not a substantialfactor in creating excessive carbon monoxide in the cooler because the emissions from theother machines would have produced excessive levels of carbon monoxide in the coolerregardless of the amount produced by its machine.

Contrary to Joe's argument, the substantial-factor test is not concerned with thequantity of the injury-producing agent or force but, rather, is concerned with its legalsignificance. See Wehmeier v. UNR Industries, Inc., 213 Ill. App. 3d 6, 31, 572 N.E.2d 320,337 (1991). Further, though a defendant has the right to rebut evidence tending to show thathis acts are negligent and a proximate cause of the plaintiff's injury and the right to establishby competent evidence that the conduct of a third person is the sole proximate cause of theplaintiff's injury (Leonardi v. Loyola University, 168 Ill. 2d 83, 101, 658 N.E.2d 450, 459(1995)), Joe's evidence falls short. Joe's did not produce competent evidence to negatecausation and to establish sole proximate cause in another's conduct. Moreover, Joe's breachof duty extended beyond emitting carbon monoxide into the work area. Joe's failure toensure that there was adequate ventilation in the work area and failure to monitor the carbonmonoxide levels in an inadequately ventilated work area contributed to plaintiff's injury.

The undisputed evidence shows that several machines were emitting carbonmonoxide gas and that some of the carbon monoxide produced by Joe's machine wascirculated into the cooler due to dissipation and a lack of cross-ventilation. Carbonmonoxide emissions from Joe's machine inextricably mixed with and became part of thecloudy haze that hung inside the cooler. The undisputed evidence shows that plaintiff wasexposed to carbon monoxide over a period of several hours while he was working in thecooler and that blood tests taken shortly after plaintiff collapsed revealed that he had a veryhigh level of carbon monoxide in his blood. Those emissions caused a single, indivisibleinjury to plaintiff.

Joe's cannot escape liability for its negligence merely because the second cleaningcompany may also be liable. Where there is more than one proximate cause of an injury, oneguilty of negligence cannot avoid responsibility merely because another person is also guiltyof negligence contributing to the same injury, even if the injury would not have occurred butfor the negligence of the other person (Sears v. Kois Brothers Equipment, Inc., 110 Ill. App.3d 884, 889, 443 N.E.2d 214, 219 (1982)) and even though the defendant's acts or omissiondid not create the source of damage (Rendleman v. ABA Building Maintenance, Inc., 222 Ill.App. 3d 367, 371, 583 N.E.2d 703, 706 (1991)). The first party is held liable because itstortious conduct was an actual and proximate cause of the plaintiff's injury, and the fact thatanother individual or entity also contributed to the plaintiff's injury does not alter theconcurring tortfeasor's responsibility for the entire indivisible injury. See Estate of Woodsv. Cole, 181 Ill. 2d 512, 519, 693 N.E.2d 333, 336-37 (1998).

In this case, the undisputed evidence demonstrates that there was a concurrent neglectof a common duty by Joe's and others and that Joe's conduct was a proximate cause of anindivisible injury to plaintiff. Based upon this record, the summary judgment was properlygranted in favor of plaintiff on the issue of liability. Accordingly, the judgment of the circuitcourt is affirmed.

Affirmed.

WELCH and GOLDENHERSH, JJ., concur.