All gas supplied to customers shall be substantially free of impurities which may cause corrosion of mains or piping or form corrosive or harmful fumes when burned in a properly designed and adjusted burner. The operating pressure on a low pressure distribution system shall be such that it will not cause unsafe operation of any connected and properly adjusted low pressure gas burning equipment. Pressure Measurements. Each utility shall make a sufficient number of pressure measurements using recording pressure gauges so that it will have a substantially accurate knowledge of the pressures provided to its customers. Pressure Records. Pressure records obtained in complying with this regulation shall be retained by the utility for at least 2 years and shall be available for inspection by the Commission's representatives. Notations on each record shall indicate the following: The location where the pressure check was made; and The time and date of the check. When the heating value of the gas distributed in the system is under the control of the utility, the following limits shall apply: Daily Btu. The average heating value on any one day may not exceed or fall below the total heating value (see COMAR 20.55.03.03B(2)) by more than 5 percent, except that the heating value may be increased by more than 5 percent during peak shaving or emergency operations in order to maintain the proper combustibility of the gas supplied to the customer. Monthly Average Btu. The monthly average heating value shall be not less than the total heating value filed in the utility's tariff. Calorimeter or Chromatograph. The utility shall provide, or designate, a calorimeter, chromatograph, or other device of a type acceptable to the Commission for the regular determination of the heating value of the gas sold. Installation. The equipment used to determine heating value shall be installed in a suitably located testing station acceptable to the Commission and subject to its inspection. Accuracy. The accuracy of all equipment used to determine heating value, as well as the method of making heating value tests, shall be acceptable to the Commission. Recording calorimeters or other equipment used to determine heating value shall be tested with a standard gas at least once each month. Records. Heating value test records shall be preserved for at least 3 years. LP-Air. The utility shall determine the heating value of LP-Air once each hour when LP-Air is being injected into the distribution system. Natural Gas and LPG. The utility shall determine the heating value of natural gas and undiluted LPG at least once each month, except that utilities selling gas subject to a thermal adjustment shall determine the heating value at least twice each day and shall make the tests during the period of the morning and afternoon peak demands. Endeavor to Avoid Interruptions. Each utility shall make reasonable efforts to avoid interruptions of service, but when interruptions occur, service shall be re-established within the shortest time practicable, consistent with safety. Notification to Commission. Each utility shall notify the Commission by telephone or telegraph of any interruption to the service of a major portion of its distribution system. Planned Interruptions. Planned interruptions shall be made at a time that will not cause unreasonable inconvenience to customers and shall be preceded by adequate notice to those who will be affected. Record of Interruptions. Each utility shall keep records of interruptions of service on its system and shall make an analysis of the records for the purpose of determining steps to be taken to prevent recurrence of interruptions. The records should include the following information concerning the interruptions: Cause; Date and time; and Duration. Public Utilities Article, §§2-121 and 5-101, Annotated Code of Maryland Effective date: July 1, 1964 (Order No. 55567) Chapter revised effective October 21, 1974 (Order No. 60922) Regulation .04A amended effective May 6, 1986 (13:9 Md. R. 1033) Regulation .05 amended effective February 7, 2000 (27:2 Md. R. 146)