StacksVerified U.S. regulatory reference

40 CFR §63.8688

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
  1. (a)You must install, operate, and maintain each continuous parameter monitoring system (CPMS) according to the following:
    1. (1)The CPMS must complete a minimum of one cycle of operation for each successive 15-minute period.
    2. (2)To determine the 3-hour average, you must:
      1. (i)Have a minimum of four successive cycles of operation to have a valid hour of data.
      2. (ii)Have valid data from at least three of four equally spaced data values for that hour from a CPMS that is not out-of-control according to your site-specific monitoring plan.
      3. (iii)Determine the 3-hour average of all recorded readings for each operating day, except as stated in § 63.8690(c). You must have at least two of the three hourly averages for that period using only hourly average values that are based on valid data (i.e., not from out-of-control periods).
    3. (3)You must record the results of each inspection, calibration, and validation check.
  2. (b)For each temperature monitoring device, you must meet the requirements in paragraph (a) of this section and the following:
    1. (1)Locate the temperature sensor in a position that provides a representative temperature.
    2. (2)For a noncryogenic temperature range, use a temperature sensor with a minimum measurement sensitivity of 2.8 °C or 1.0 percent of the temperature value, whichever is larger.
    3. (3)If a chart recorder is used, it must have a sensitivity in the minor division of at least 20 °F.
    4. (4)Perform an accuracy check at least semiannually or following an operating parameter deviation:
      1. (i)According to the procedures in the manufacturer's documentation; or
      2. (ii)By comparing the sensor output to redundant sensor output; or
      3. (iii)By comparing the sensor output to the output from a calibrated temperature measurement device; or
      4. (iv)By comparing the sensor output to the output from a temperature simulator.
    5. (5)Conduct accuracy checks any time the sensor exceeds the manufacturer's specified maximum operating temperature range or install a new temperature sensor.
    6. (6)At least quarterly or following an operating parameter deviation, perform visual inspections of components if redundant sensors are not used.
  3. (c)For each pressure measurement device, you must meet the requirements of paragraph (a) of this section and the following:
    1. (1)Locate the pressure sensor(s) in, or as close as possible, to a position that provides a representative measurement of the pressure.
    2. (2)Use a gauge with a minimum measurement sensitivity of 0.12 kiloPascals or a transducer with a minimum measurement sensitivity of 5 percent of the pressure range.
    3. (3)Check pressure tap pluggage daily. Perform an accuracy check at least quarterly or following an operating parameter deviation:
      1. (i)According to the procedures in the manufacturer's documentation; or
      2. (ii)By comparing the sensor output to redundant sensor output.
    4. (4)Conduct calibration checks any time the sensor exceeds the manufacturer's specified maximum operating pressure range or install a new pressure sensor.
    5. (5)At least monthly or following an operating parameter deviation, perform a leak check of all components for integrity, all electrical connections for continuity, and all mechanical connections for leakage.
    6. (6)At least quarterly or following an operating parameter deviation, perform visible inspections on all components if redundant sensors are not used.
  4. (d)For monitoring parameters other than temperature and pressure drop, you must install and operate a CPMS to provide representative measurements of the monitored parameters.
  5. (e)For each flare, you must install a device (including but not limited to a thermocouple, an ultraviolet beam sensor, or an infrared sensor) capable of continuously detecting the presence of a pilot flame.
  6. (f)As an option to installing the CPMS specified in paragraph (a) of this section, you may install a continuous emissions monitoring system (CEMS) or a continuous opacity monitoring system (COMS) that meets the applicable requirements in § 63.8 according to Table 7 to this subpart and the applicable performance specifications of 40 CFR part 60, appendix B.
  7. (g)For each monitoring system required in this section, you must develop and make available for inspection by the permitting authority, upon request, a site-specific monitoring plan that addresses the following:
    1. (1)Installation of the CPMS, CEMS, or COMS sampling probe or other interface at a measurement location relative to each affected process unit such that the measurement is representative of control of the exhaust emissions (e.g., on or downstream of the last control device);
    2. (2)Performance and equipment specifications for the sample interface, the pollutant concentration or parametric signal analyzer, and the data collection and reduction system; and
    3. (3)Performance evaluation procedures and acceptance criteria (e.g., calibrations).
  8. (h)In your site-specific monitoring plan, you must also address the following:
    1. (1)Ongoing operation and maintenance procedures in accordance with the general requirements of § 63.8(c)(1)(ii), (c)(3), (c)(4)(ii), and (c)(7) and (8);
    2. (2)Ongoing data quality assurance procedures in accordance with the general requirements of § 63.8(d); and
    3. (3)Ongoing recordkeeping and reporting procedures in accordance with §§ 63.8693 and 63.8694 and the general requirements of § 63.10(e)(1) and (e)(2)(i).
      1. (i)You must conduct a performance evaluation of each CPMS, CEMS, or COMS in accordance with your site-specific monitoring plan.
  9. (j)You must operate and maintain the CPMS, CEMS, or COMS in continuous operation according to the site-specific monitoring plan.