Defendant states in its brief that “[i]t is not our position that the acts specified by the Industrial Commission did not occur, but that these acts were not negligent acts in the circumstances of this case and that the evidence does not support such a finding.” Thus the only questions presented to us concern the sufficiency of the Commission’s findings of fact to support its conclusions concerning negligence and contributory negligence. See Bailey v. N.C. Dept. of Mental Health, 272 N.C. 680, 159 S.E. 2d 28 (1968); Tanner v. Dept. of Correction, 19 N.C. App. 689, 200 S.E. 2d 350 (1973).
Defendant correctly points out that it should be held liable only for injuries which were reasonably foreseeable from use of the machine under these conditions. Bennett v. Southern Ry. Co., 245 N.C. 261, 96 S.E. 2d 31, 62 A.L.R. 2d 785 (1957), cert. den., 353 U.S. 958, 1 L.Ed. 2d 909, 77 S.Ct. 865. It then contends that since the machine worked under test conditions at 8:00 p.m., the defendant’s employees had no reason to anticipate any danger of explosion later in the evening just because the water had continued to heat in a machine without any thermostat controls. The evidence showed that the machine did not conform to the Winston-Salem Heating Code which required it to have a thermostat. In some circumstances, violation of a safety ordinance is negligence per se. Bell v. Page, 271 N.C. 396, 156 S.E. 2d 711 (1967). Even were this not so, proof of violation of a safety ordinance is evidence of negligence. In either event the Industrial Commission had ample evidence before it to find that defendant’s employees violated their duty of care to plaintiff. Thus if the facts as found by the Commission show that an explosion was a foreseeable risk from the use of the machine under the conditions *4found during the performance, then the conclusion that defendant’s employees were negligent has been fully supported.
It is an elementary concept of science that the pressure inside a closed container increases as the temperature of the liquid or gas contained in it increases. It is also a matter of common knowledge that the longer one applies heat to a liquid or gas, the hotter that liquid or gas will grow. Just as the lid will begin to rattle when a covered pot is left too long on the stove, the top of the fog machine was bound to become insecure if too much heat was allowed to build up inside the drum. Thus it was foreseeable that an explosion could occur if the heat of the contents was not controlled. The Commission found that sandbags were normally used to hold the lid in place. This indicates an awareness by the school personnel of the danger of pressure buildup in the machine. If defendant’s employees were on notice of the danger and continued to heat the water so as to increase it, then these facts support a finding of actionable negligence on their part.
The defendant next contends that if these actions constituted negligence on the part of its employees, then they must also constitute negligence on plaintiff’s part in that she had knowledge, capacity and duties similar to those of the negligent employees. We point out, however, that the Commission found from competent evidence that plaintiff did not take part in the test of the machine. Moreover, Susan Summers, the stage manager, testified that plaintiff “was a student helping out .... Her job was to do what I or Mary Wayne told her to do.” At the time of the explosion she was going about her assigned duties as Mary Wayne, the supervisor of the Dome Theatre, tended to the machine. No evidence showed that she was at any time responsible for turning it on or off, or that she had any knowledge of how long it had been heating. In Moody v. Kersey, 270 N.C. 614, 155 S.E. 2d 215 (1967), the Court held that where a plaintiff engaged in his own work stayed on the job even after he overheard his supervisor report a condition which later proved to be unsafe, he was not contributorily negligent as a matter of law. The Court pointed out that he had no reason to believe that his supervisor would expose him to danger from an unsafe condition. See also Lewis v. Barnhill, 267 N.C. 457, 148 S.E. 2d 536 (1966). A seventeen-year-old girl should equally be able to rely on the employees of her school not to expose her to danger and in the absence of evidence that she *5was aware of all the facts which made up negligence on their behalf, she should not be held contributorily negligent as a matter of law. Since the Industrial Commission’s findings of fact do not compel the conclusion that plaintiff failed to exercise due care for her own safety, the conclusion that there was no contributory negligence on her part is without error.
Chief Judge BROCK and Judge MARTIN concur.