Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:9:p25
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 9 (pt 25/37)
Character Range: 1848163–1851230

may not differ by more than 3 per cent from the hydrocarbon mass given in paragraph 4.2.3.3.7. of this annex.
              4.2.3.4. Calculations
               The calculation of net hydrocarbon mass change within the enclosure is used to determine the chamber's hydrocarbon background and leak rate. Initial and final readings of hydrocarbon concentration, temperature and barometric pressure are used to calculate the mass change.

              The calculation shall be undertaken in accordance with the equation in either paragraph 7.1. or alternatively paragraph 7.1.1. of this annex, using the following value for V.

               V is the net enclosure volume, m3.

              4.3. Analytical systems
              The analytical systems shall meet the requirements of paragraphs 4.3.1. to. 4.3.3. of this annex.
              Continuous measuring of hydrocarbons is not mandatory unless the fixed volume type enclosure is used.
              4.3.1. Hydrocarbon analyser
              4.3.1.1. The atmosphere within the chamber is monitored using a hydrocarbon detector of the FID type. Sample gas shall be drawn from the mid-point of one side wall or roof of the chamber and any bypass flow shall be returned to the enclosure, preferably to a point immediately downstream of the mixing fan.
              4.3.1.2. The hydrocarbon analyser shall have a response time to 90 per cent of final reading of less than 1.5 seconds. Its stability shall be better than 2 per cent of full scale at zero and at 80  20 per cent of full scale over a 15-minute period for all operational ranges.
              4.3.1.3. The repeatability of the analyser expressed as one standard deviation shall be better than 1 per cent of full scale deflection at zero and at 80  20 per cent of full scale on all ranges used.
              4.3.1.4. The operational ranges of the analyser shall be chosen to give best resolution over the measurement, calibration and leak checking procedures.
              4.3.2. Hydrocarbon analyser data recording system
              4.3.2.1. The hydrocarbon analyser shall be fitted with a device to record electrical signal output either by strip chart recorder or other data processing system at a frequency of at least once per minute. The recording system shall have operating characteristics at least equivalent to the signal being recorded and shall provide a permanent record of results. The record shall show a positive indication of the beginning and end of the hot soak or diurnal emission test (including beginning and end of sampling periods along with the time elapsed between start and completion of each test).
              4.3.3. Checking of FID hydrocarbon analyser
              4.3.3.1. Detector response optimisation
               The FID shall be adjusted as specified by the instrument manufacturer. Propane in air should be used to optimise the response on the most common operating range.
              4.3.3.2. Calibration of the hydrocarbon analyser
               The analyser should be calibrated using propane in