Opinion by
Mr. Justice Eagen,On the afternoon of November 18, 1959, Carl F. Davies and his wife, Mary E. Davies, visited the business office of J. Fred Thomas in the City of Sharon, Pennsylvania. A tragic accident ensued. Carbon monoxide poisoning caused the deaths of both J. Fred Thomas and Mary E. Davies and resulted in serious injuries to Carl F. Davies. Actions for damages on behalf of Carl F. Davies and the Estate of Mary E. Davies against Thomas’s Estate failed when the court below entered judgments of compulsory nonsuit. Plaintiffs appeal.
The determinative issue is: Was the proof at trial legally sufficient to warrant the submission of • the question of negligence to the jury? In evaluating the *211testimony in this respect, the record must necessarily be read in the light most favorable to the plaintiffs’ cause: Weisman v. Sander Chevrolet Co., 402 Pa. 272, 167 A. 2d 308 (1961); McKniff v. Wilson, 404 Pa. 647, 172 A. 2d 801 (1961).
The facts established by the plaintiffs may be summarized as follows: Thomas was the stepfather of Mrs. Davies. He was seventy-one years of age and lived alone. He suffered a stroke and had been seriously ill in the months immediately prior to his death and during this period, while being constantly treated by his physician, had stayed in the Davies home. The doctor advised against his operating his automobile and Mr. Davies had agreed to drive him anywhere he desired to go.
Thomas was an engineer and maintained his office in the Thomas Building in Sharon, which he owned and solely occupied. At about 3:45 o’clock on the day involved, his physician was called to the Thomas office by Mrs. Davies. Upon arrival, he found Thomas, unconscious, with Mr. and Mrs. Davies attempting to aid and revive him. The physician remained there about thirty-five minutes, and succeeded in bringing Thomas back to a state of partial consciousness. Mr. and Mrs. Davies advised the doctor that they would remain with Thomas until he had recovered sufficiently to be taken to their home for further care.
Shortly after ten o’clock that same night, a police officer visited the Thomas office and found Thomas and Mrs. Davies dead. Mr. Davies was unconscious. An autopsy revealed the cause of death to be carbon monoxide poisoning. An examination of the premises determined the source of the poisonous gas to be a rusted shut damper in the chimney flue pipe leading from the gas-burning furnace which heated the premises. This damper was located inside the flue pipe on top of the furnace, about seven feet off the floor,
*212A heating expert testified. He was shown a photograph of the flue pipe and damper involved, and opined that the installation of a damper in a pipe leading from a furnace to a chimney is improper and unsafe because “It may become lodged or in a closed position and rust shut____”
It is argued that the doctrine of “exclusive control” governs the instant facts and that, therefore, the burden of coming forward with evidence to establish freedom from negligence was upon the defendant. This is not correct.
It has long been established that the mere showing of an accident and injury will not make out a case for the jury: Rennekamp v. Blair, 375 Pa. 620, 101 A. 2d 669 (1954); DiGiannantonio v. Pgh. Rwys. Co., 402 Pa. 27, 166 A. 2d 28 (1960). Fundamentally, the burden of furnishing proof of the existence of negligence is upon those who assert it. However, since the purpose of a trial is to elicit the truth, the doctrine of “exclusive control” has been applied in those cases and those only wherein the evidence as to the cause of the accident is peculiarly or exclusively within the possession of the defendant or defendants and not equally available to the plaintiffs. The basis of the rule being that those who alone know the facts are the ones who should in justice be called upon to reveal them. See, Scott v. The London and St. Katherine Docks Co., 3 Hurlstone & Coltman, 596; Mack v. Reading Co., 377 Pa. 135, 103 A. 2d 749 (1954); First Methodist Episcopal Church v. Bangor Gas Co., 388 Pa. 115, 130 A. 2d 517 (1957); Haddon v. Lotito, 399 Pa. 521, 161 A. 2d 160 (1960).
It is patently clear that this is not a case wherein proof of the cause of the accident was “peculiarly” or “exclusively” within the knowledge of the defendant, the administrator of Thomas’s Estate. The doctrine, therefore, does not apply.
*213It is asserted that under the evidence the jury could conclude that Mr. and Mrs. Davies were “business visitors” in the Thomas office on the occasion involved, and that the court below erred in concluding that they were merely social guests. If they were “business visitors” the duty of the owner would be to exercise reasonable care in maintaining the premises in a safe condition: Matthews v. Spiegel, 385 Pa. 203, 122 A. 2d 696 (1956) and Slobodzian v. Beighley, 401 Pa. 520, 164 A. 2d 923 (1960).
There is no specific evidence in the record as to why they visited the Thomas office on the occasion involved. The proof does show that when the physician left they remained there in order to take Thomas to their home when he was physically able. From the relationship existing between the parties and their past close association, the only reasonable conclusion is that they were social guests. Their mere presence upon the premises raises no presumption that they were “business visitors.” That they were such may not be conjectured. Nor does the fact that a social guest performs some minor or incidental service for his host during his stay convert the status to that of “business visitor.” See, Lubenow v. Cook, 137 Conn. 611, 79 A. 2d 826 (1951); McHenry v. Howells (Oregon), 272 P. 2d 210 (1954); Dotson v. Haddock (Wash.), 278 P. 2d 338 (1955); Ciaglo v. Ciaglo (Ill.), 156 N.E. 2d 376 (1959); Murrell v. Handley (N.C.), 96 S.E. 2d 717 (1957); 25 A.L.R. 2d 598.
Social guests are gratuitous licensees. To this class, the owner of a premises is liable for bodily harm caused by a latent dangerous condition existing thereon only if he has knowledge of the condition and fails to give warning thereof, realizing that it involves an unreasonable risk to his guests and that they are not likely to discover its existence, Restatement, Torts, §342; Rushton v. Winters, 331 Pa. 78, 200 A. 60 (1938); Bow*214ser v. Artman, 363 Pa. 388, 69 A. 2d 836 (1949) and Slobodzian v. Beighley, supra. There is not a scintilla of evidence herein to establish that the deceased, Thomas, had any previous knowledge of the existence of the latent dangerous condition upon which the cause of action is based.
Judgments affirmed.