California Air Resources Board

Potential Amendments to the California Exhaust Emission Standards and Test Procedures for New 2013 and Later Small Off-Road Engines; Engine-Testing Procedures (Part 1065) as of March 24, 2021.

This page consists of material released as part of the development process for the Proposed Amendments to the Small Off-Road Engine (SORE) Regulations.

For the Proposed Amendments and other rulemaking documents that the Board will consider for adoption during the public hearing in December 2021, please refer to the SORE rulemaking page.

(Note: The potential amendments are shown in underline to indicate additions and strikeout to indicate deletions from the existing regulatory text.)

Subpart C–Measurement Instruments

§ 1065.201 Overview and general provisions.

(a) Scope. This subpart specifies measurement instruments and associated system requirements related to emission testing in a laboratory or similar environment and in the field. This includes laboratory instruments and portable emission measurement systems (PEMS) for measuring engine parameters, ambient conditions, flow‑related parameters, and emission concentrations.

(b) Instrument types. You may use any of the specified instruments as described in this subpart to perform emission tests. If you want to use one of these instruments in a way that is not specified in this subpart, or if you want to use a different instrument, you must first get us to approve your alternate procedure under § 1065.10. Where we specify more than one instrument for a particular measurement, we may identify which instrument serves as the reference for comparing with an alternate procedure. You may generally use instruments with compensation algorithms that are functions of other gaseous measurements and the known or assumed fuel properties for the test fuel. The target value for any compensation algorithm is 0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.

(c) Measurement systems. Assemble a system of measurement instruments that allows you to show that your engines comply with the applicable emission standards, using good engineering judgment. When selecting instruments, consider how conditions such as vibration, temperature, pressure, humidity, viscosity, specific heat, and exhaust composition (including trace concentrations) may affect instrument compatibility and performance.

(d) Redundant systems. For all measurement instruments described in this subpart, you may use data from multiple instruments to calculate test results for a single test. If you use redundant systems, use good engineering judgment to use multiple measured values in calculations or to disregard individual measurements, as appropriate. Note that you must keep your results from all measurements, as described in § 1065.25. This requirements This requirement applies whether or not you actually use the measurements in your calculations.

(e) Range. You may use an instrument's response above 100% of its operating range if this does not affect your ability to show that your engines comply with the applicable emission standards. Note that we require additional testing and reporting if an analyzer responds above 100% of its range. See § 1065.550. Auto‑ranging analyzers do not require additional testing or reporting.

(f) Related subparts for laboratory testing. Subpart D of this part describes how to evaluate the performance of the measurement instruments in this subpart. In general, if an instrument is specified in a specific section of this subpart, its calibration and verifications are typically specified in a similarly numbered section in subpart D of this part. For example, § 1065.290 gives instrument specifications for PM balances and § 1065.390 describes the corresponding calibrations and verifications. Note that some instruments also have other requirements in other sections of subpart D of this part. Subpart B of this part identifies specifications for other types of equipment, and subpart H of this part specifies engine fluids and analytical gases.

(g) Field testing and testing with PEMS. Subpart J of this part describes how to use these and other measurement instruments for field testing and other PEMS testing.

(h) Recommended practices. This subpart identifies a variety of recommended but not required practices for proper measurements. We believe in most cases it is necessary to follow these recommended practices for accurate and repeatable measurements. However, we do not specifically require you to follow these recommended practices to perform a valid test, as long as you meet the required calibrations and verifications of measurement systems specified in subpart D of this part. Similarly, we are not required to follow all recommended practices, as long as we meet the required calibrations and verifications. Our decision to follow or not follow a given recommendation when testing your engine is not dependent on whether or not youwe perform a test does not depend on whether you followed it during your testing.

§ 1065.202 Data updating, recording, and control.

Your test system must be able to update data, record data and control systems related to operator demand, the dynamometer, sampling equipment, and measurement instruments. Set up the measurement and recording equipment to avoid aliasing by ensuring that the sampling frequency is at least double that of the signal you are measuring; this may require increasing the sampling rate or filtering the signal. Use data acquisition and control systems that can record at the specified minimum frequencies, as follows:

Table 1 of § 1065.202—Data Recording and Control Minimum Frequencies

§ 1065.205 Performance specifications for measurement instruments.

Your test system as a whole must meet all the applicable calibrations, verifications, and test‑validation criteria specified in subparts D and F of this part or subpart J of this part for using PEMS and for performing field testing. outside this section for laboratory testing or field testing, as applicable. We recommend that your instruments meet the specifications in Table 1 of this section for all ranges you use for testing. We also recommend that you keep any documentation you receive from instrument manufacturers showing that your instruments meet the specifications in Table 1 of this section. the following table:

Table 1 of §1065.205—RECOMMENDED PERFORMANCE SPECIFICATIONS FOR MEASUREMENT INSTRUMENTSRecommended Performance Specifications For Measurement Instruments

Measurement of Engine Parameters and Ambient Conditions

§ 1065.210 Work input and output sensors.

(a) Application. Use instruments as specified in this section to measure work inputs and outputs during engine operation. We recommend that you use sensors, transducers, and meters that meet the specifications in Table 1 of § 1065.205. Note that your overall systems for measuring work inputs and outputs must meet the linearity verifications in § 1065.307. We recommend that you measure work inputs and outputs where they cross the system boundary as shown in Figure 1 of § 1065.210. The system boundary is different for air‑cooled engines than for liquid‑cooled engines. If you choose to measure work before or after a work conversion, relative to the system boundary, use good engineering judgment to estimate any work‑conversion losses in a way that avoids overestimation of total work. For example, if it is impractical to instrument the shaft of an exhaust turbine generating electrical work, you may decide to measure its converted electrical work. As another example, you may decide to measure the tractive (i.e., electrical output) power of a locomotive, rather than the brake power of the locomotive engine. In these cases, divide the electrical work by accurate values of electrical generator efficiency (η<1), or assume an efficiency of 1 (η=1), which would over‑estimate brake‑specific emissions. For the example of using locomotive tractive power with a generator efficiency of 1 (η=1), this means using the tractive power as the brake power in emission calculations. Do not underestimate any work conversion efficiencies for any components outside the system boundary that do not return work into the system boundary. And do not overestimate any work conversion efficiencies for components outside the system boundary that do return work into the system boundary. In all cases, ensure that you are able to accurately demonstrate compliance with the applicable standards.

Figure 1 of § 1065.210: Work inputs, outputs, and system boundaries for liquid-cooled and air-cooled engines.

(b) Shaft work. Use speed and torque transducer outputs to calculate total work according to § 1065.650.

(1) Speed. Use a magnetic or optical shaft‑position detector with a resolution of at least 60 counts per revolution, in combination with a frequency counter that rejects common‑mode noise.

(2) Torque. You may use a variety of methods to determine engine torque. As needed and appropriate, and based on good engineering judgment, compensate for torque induced by the inertia of accelerating and decelerating components connected to the flywheel, such as the drive shaft and dynamometer rotor. Use any of the following methods to determine engine torque:

(i) Measure torque by mounting a strain gage or similar instrument in‑line between the engine and dynamometer.

(ii) Measure torque by mounting a strain gage or similar instrument on a lever arm connected to the dynamometer housing.

(iii) Calculate torque from internal dynamometer signals, such as armature current, as long as you calibrate this measurement as described in § 1065.310.

(c) Electrical work. Use a watt‑hour meter output to calculate total work according to § 1065.650. Use a watt‑hour meter that outputs active power (kW). Watt‑hour meters typically combine a Wheatstone bridge voltmeter and a Hall‑effect clamp‑on ammeter into a single microprocessor‑based instrument that analyzes and outputs several parameters, such as alternating or direct current voltage (V), current (A), power factor (pf), apparent power (VA), reactive power (VAR), and active power (W).

(d) Pump, compressor or turbine work. Use pressure transducer and flow‑meter outputs to calculate total work according to § 1065.650. For flow meters, see § 1065.220 through § 1065.248.

§ 1065.215 Pressure transducers, temperature sensors, and dewpoint sensors.

(a) Application. Use instruments as specified in this section to measure pressure, temperature, and dewpoint.

(b) Component requirements. We recommend that you use pressure transducers, temperature sensors, and dewpoint sensors that meet the specifications in Table 1 of § 1065.205. Note that your overall systems for measuring pressure, temperature, and dewpoint must meet the calibration and verifications in § 1065.315.

(c) Temperature. For PM‑balance environments or other precision temperature measurements over a narrow temperature range, we recommend thermistors. For other applications we recommend thermocouples that are not grounded to the thermocouple sheath. You may use other temperature sensors, such as resistive temperature detectors (RTDs).

(d) Pressure. Pressure transducers must be located in a temperature‑controlled environment, or they must compensate for temperature changes over their expected operating range. Transducer materials must be compatible with the fluid being measured. For atmospheric pressure or other precision pressure measurements, we recommend either capacitance‑type, quartz crystal, or laser‑interferometer transducers. For other applications, we recommend either strain gage or capacitance‑type pressure transducers. You may use other pressure‑measurement instruments, such as manometers, where appropriate.

(e) Dewpoint. For PM‑stabilization environments, we recommend chilled‑surface hygrometers, which include chilled mirror detectors and chilled surface acoustic wave (SAW) detectors. For other applications, we recommend thin‑film capacitance sensors. You may use other dewpoint sensors, such as a wet‑bulb/dry‑bulb psychrometer, where appropriate.

Flow-Related Measurements

§ 1065.220 Fuel flow meter.

(a) Application. You may use fuel flow meters in combination with a chemical balance of carbon (or oxygen) between the fuel, inlet intake air, and raw exhaust to calculate raw exhaust flow as described in § 1065.650 § 1065.655(f)., as follows: You may also use fuel flow meters to determine the mass flow rate of carbon‑carrying fuel streams for performing carbon balance error verification in §1065.543 and to calculate the mass of those fuel streams as described in §1065.643. The following provisions apply for using fuel flow meters:

(1) Use the actual value of calculated raw exhaust flow rate in the following cases:

(i) For multiplying raw exhaust flow rate with continuously sampled concentrations.

(ii) For multiplying total raw exhaust flow with batch‑sampled concentrations.

(iii) For calculating the dilution air flow for background correction as described in §1065.667

(2) In the following cases, you may use a fuel flow meter signal that does not give the actual value of raw exhaust, as long as it is linearly proportional to the exhaust molar flow rate's actual calculated value:

(i) For feedback control of a proportional sampling system, such as a partial‑flow dilution system.

(ii) For multiplying with continuously sampled gas concentrations, if the same signal is used in a chemical‑balance calculation to determine work from brake‑specific fuel consumption and fuel consumed.

(b) Component requirements. We recommend that you use a fuel flow meter that meets the specifications in Table 1 of § 1065.205. We recommend a fuel flow meter that measures mass directly, such as one that relies on gravimetric or inertial measurement principles. This may involve using a meter with one or more scales for weighing fuel or using a Coriolis meter. Note that your overall system for measuring fuel flow must meet the linearity verification in § 1065.307 and the calibration and verifications in § 1065.320.

(c) Recirculating fuel. In any fuel‑flow measurement, account for any fuel that bypasses the engine or returns from the engine to the fuel storage tank.

(d) Flow conditioning. For any type of fuel flow meter, condition the flow as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. You may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, straightening fins, or pneumatic pulsation dampeners to establish a steady and predictable velocity profile upstream of the meter. Condition the flow as needed to prevent any gas bubbles in the fuel from affecting the fuel meter.

§ 1065.225 Intake‑air flow meter.

(a) Application. You may use an intake‑air flow meters in combination with a chemical balance of carbon (or oxygen) between the fuel, inlet intake air, and raw exhaust to calculate raw exhaust flow as described in § 1065.650, as follows 1065.655(f) and (g). You may also use intake‑air flow meters to determine the amount of intake air input for performing carbon balance error verification in §1065.543 and to calculate the measured amount of intake air, n_int, as described in §1065.643. The following provisions apply for using intake air flow meters:

(1) Use the actual value of calculated raw exhaust in the following cases:

(i) For multiplying raw exhaust flow rate with continuously sampled concentrations.

(ii) For multiplying total raw exhaust flow with batch‑sampled concentrations.

(iii) For verifying minimum dilution ratio for PM batch sampling as described in §1065.546.

(iv) For calculating the dilution air flow for background correction as described in §1065.667.

(2) In the following cases, you may use an intake‑air flow meter signal that does not give the actual value of raw exhaust, as long as it is linearly proportional to the exhaust flow rate's actual calculated value:

(i) For feedback control of a proportional sampling system, such as a partial‑flow dilution system.

(ii) For multiplying with continuously sampled gas concentrations, if the same signal is used in a chemical‑balance calculation to determine work from brake‑specific fuel consumption and fuel consumed.

(b) Component requirements. We recommend that you use an intake‑air flow meter that meets the specifications in Table 1 of § 1065.205. This may include a laminar flow element, an ultrasonic flow meter, a subsonic venturi, a thermal‑mass meter, an averaging Pitot tube, or a hot‑wire anemometer. Note that your overall system for measuring intake‑air flow must meet the linearity verification in § 1065.307 and the calibration in § 1065.325.

(c) Flow conditioning. For any type of intake‑air flow meter, condition the flow as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. You may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, orifice plates or straightening fins to establish a predictable velocity profile upstream of the meter.

§ 1065.230 Raw exhaust flow meter.

(a) Application. You may use measured raw exhaust flow, as follows:

(1) Use the actual value of calculated raw exhaust in the following cases:

(i) Multiply raw exhaust flow rate with continuously sampled concentrations.

(ii) Multiply total raw exhaust with batch sampled concentrations.

(2) In the following cases, you may use a raw exhaust flow meter signal that does not give the actual value of raw exhaust, as long as it is linearly proportional to the exhaust flow rate's actual calculated value:

(i) For feedback control of a proportional sampling system, such as a partial‑flow dilution system.

(ii) For multiplying with continuously sampled gas concentrations, if the same signal is used in a chemical‑balance calculation to determine work from brake‑specific fuel consumption and fuel consumed.

(b) Component requirements. We recommend that you use a raw‑exhaust flow meter that meets the specifications in Table 1 of § 1065.205. This may involve using an ultrasonic flow meter, a subsonic venturi, an averaging Pitot tube, a hot‑wire anemometer, or other measurement principle. This would generally not involve a laminar flow element or a thermal‑mass meter. Note that your overall system for measuring raw exhaust flow must meet the linearity verification in § 1065.307 and the calibration and verifications in § 1065.330. Any raw‑exhaust meter must be designed to appropriately compensate for changes in the raw exhaust's thermodynamic, fluid, and compositional states.

(c) Flow conditioning. For any type of raw exhaust flow meter, condition the flow as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. You may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, orifice plates or straightening fins to establish a predictable velocity profile upstream of the meter.

(d) Exhaust cooling. You may cool raw exhaust upstream of a raw‑exhaust flow meter, as long as you observe all the following provisions:

(1) Do not sample PM downstream of the cooling.

(2) If cooling causes exhaust temperatures above 202 °C to decrease to below 180 °C, do not sample NMHC downstream of the cooling for testing under this Part compression‑ignition engines, 2‑stroke spark‑ignition engines, and 4‑stroke spark‑ignition engines below 19 kW.

(3) If cooling causes aqueous condensation, do not sample NO_X downstream of the cooling unless the cooler meets the performance verification in § 1065.376.

(4) If cooling causes aqueous condensation before the flow reaches a flow meter, measure dewpoint, T dew and pressure, p total at the flow meter inlet. Use these values in emission calculations according to § 1065.650.

§ 1065.240 Dilution air and diluted exhaust flow meters.

(a) Application. Use a diluted exhaust flow meter to determine instantaneous diluted exhaust flow rates or total diluted exhaust flow over a test interval. You may use the difference between a diluted exhaust flow meter and a dilution air meter to calculate raw exhaust flow rates or total raw exhaust flow over a test interval.

(b) Component requirements. We recommend that you use a diluted exhaust flow meter that meets the specifications in Table 1 of § 1065.205. Note that your overall system for measuring diluted exhaust flow must meet the linearity verification in § 1065.307 and the calibration and verifications in § 1065.340 and § 1065.341. You may use the following meters:

(1) For constant‑volume sampling (CVS) of the total flow of diluted exhaust, you may use a critical‑flow venturi (CFV) or multiple critical‑flow venturis arranged in parallel, a positive‑displacement pump (PDP), a subsonic venturi (SSV), or an ultrasonic flow meter (UFM). Combined with an upstream heat exchanger, either a CFV or a PDP will also function as a passive flow controller in a CVS system. However, you may also combine any flow meter with any active flow control system to maintain proportional sampling of exhaust constituents. You may control the total flow of diluted exhaust, or one or more sample flows, or a combination of these flow controls to maintain proportional sampling.

(2) For any other dilution system, you may use a laminar flow element, an ultrasonic flow meter, a subsonic venturi, a critical‑flow venturi or multiple critical‑flow venturis arranged in parallel, a positive‑displacement meter, a thermal‑mass meter, an averaging Pitot tube, or a hot‑wire anemometer.

(c) Flow conditioning. For any type of diluted exhaust flow meter, condition the flow as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. For some meters, you may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, orifice plates or straightening fins to establish a predictable velocity profile upstream of the meter.

(d) Exhaust cooling. You may cool diluted exhaust upstream of a dilute‑exhaust flow meter, as long as you observe all the following provisions:

(1) Do not sample PM downstream of the cooling.

(2) If cooling causes exhaust temperatures above 202 °C to decrease to below 180 °C, do not sample NMHC downstream of the cooling for compression‑ignition engines, 2‑stroke spark‑ignition engines, and 4‑stroke spark‑ignition engines below 19 kW engines tested under this part.

(3) If cooling causes aqueous condensation, do not sample NO_X downstream of the cooling unless the cooler meets the performance verification in § 1065.376. The cooling must not cause aqueous condensation, as described in § 1065.140(c)(6).

(4) If cooling causes aqueous condensation before the flow reaches a flow meter, measure dewpoint, T_dew and pressure, p_total at the flow meter inlet. Use these values in emission calculations according to § 1065.650.

§ 1065.245 Sample flow meter for batch sampling.

(a) Application. Use a sample flow meter to determine sample flow rates or total flow sampled into a batch sampling system over a test interval. You may use the difference between a diluted exhaust sample flow meter and a dilution air meter to calculate raw exhaust flow rates or total raw exhaust flow over a test interval.

(b) Component requirements. We recommend that you use a sample flow meter that meets the specifications in Table 1 of § 1065.205. This may involve a laminar flow element, an ultrasonic flow meter, a subsonic venturi, a critical‑flow venturi or multiple critical‑flow venturis arranged in parallel, a positive‑displacement meter, a thermal‑mass meter, an averaging Pitot tube, or a hot‑wire anemometer. Note that your overall system for measuring sample flow must meet the linearity verification in § 1065.307. For the special case where CFVs are used for both the diluted exhaust and sample‑flow measurements and their upstream pressures and temperatures remain similar during testing, you do not have to quantify the flow rate of the sample‑flow CFV. In this special case, the sample‑flow CFV inherently flow‑weights the batch sample relative to the diluted exhaust CFV.

(c) Flow conditioning. For any type of sample flow meter, condition the flow as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. For some meters, you may accomplish this by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, orifice plates or straightening fins to establish a predictable velocity profile upstream of the meter.

§ 1065.248 Gas divider.

(a) Application. You may use a gas divider to blend calibration gases.

(b) Component requirements. Use a gas divider that blends gases to the specifications of § 1065.750 and to the flow‑weighted concentrations expected during testing. You may use critical‑flow gas dividers, capillary‑tube gas dividers, or thermal‑mass‑meter gas dividers. Note that your overall gas‑divider system must meet the linearity verification in § 1065.307.

CO and CO₂ Measurements

§ 1065.250 Nondispersive infra‑red analyzer.

(a) Application. Use a nondispersive infra‑red (NDIR) analyzer to measure CO and CO₂ concentrations in raw or diluted exhaust for either batch or continuous sampling.

(b) Component requirements. We recommend that you use an NDIR analyzer that meets the specifications in Table 1 of § 1065.205. Note that your NDIR‑based system must meet the calibration and verifications in §§ 1065.350 and § 1065.355 and it must also meet the linearity verification in § 1065.307. You may use an NDIR analyzer that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.

Hydrocarbon Measurements

§ 1065.260 Flame-ionization detector.

(a) Application. Use a flame‑ionization detector (FID) analyzer to measure hydrocarbon concentrations in raw or diluted exhaust for either batch or continuous sampling. Determine hydrocarbon concentrations on a carbon number basis of one, C₁. Determine methane and nonmethane hydrocarbon values as described in paragraph (e) For measuring THC or THCE you must use a FID analyzer. For measuring CH₄ you must meet the requirements of paragraph (f) of this section. See subpart I of this part for special provisions that apply to measuring hydrocarbons when testing with oxygenated fuels.

(b) Component requirements. We recommend that you use a FID analyzer that meets the specifications in Table 1 of § 1065.205. Note that your FID‑based system for measuring THC, THCE, or CH₄ must meet all of the verifications for hydrocarbon measurement in subpart D of this part, and it must also meet the linearity verification in § 1065.307. You may use a FID that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.

(c) Heated FID analyzers. For measuring THC or THCE compression‑ignition engines, two‑stroke spark‑ignition engines, and four‑stroke spark‑ignition enginesbelow 19 kW, you must use heated FID analyzers that maintain all surfaces that are exposed to emissions at a temperature of (191 ± 11) °C.

(d) FID fuel and burner air. Use FID fuel and burner air that meet the specifications of § 1065.750. Do not allow the FID fuel and burner air to mix before entering the FID analyzer to ensure that the FID analyzer operates with a diffusion flame and not a premixed flame.

(e) Methane. FID analyzers measure total hydrocarbons (THC). To determine nonmethane hydrocarbons (NMHC), quantify methane, CH₄, either with a nonmethane cutter and a FID analyzer as described in § 1065.265, or with a gas chromatograph as described in § 1065.267. Instead of measuring methane, you may assume that 2% of measured total hydrocarbon is methane, as described in § 1065.650(c)(1)(vi). For a FID analyzer used to determine NMHC, determine its response factor to methane, RF_CH4, as described in § 1065.360. Note that NMHC‑related calculations are described in § 1065.660. NMHC and NMOG. For demonstrating compliance with NMHC standards, you may either measure THC and determine NMHC mass as described in §1065.660(b)(1), or you may measure THC and CH₄ and determine NMHC as described in §1065.660(b)(2) or (3). You may also use the additive method in §1065.660(b)(4) for natural gas‑fueled engines as described in §1065.266.

(f) NMNEHC. For demonstrating compliance with NMNEHC standards, you may either measure NMHC or determine NMNEHC mass as described in § 1065.660(c)(1), you may measure THC, CH₄, and C₂H₆ and determine NMNEHC as described in § 1065.660(c)(2), or you may use the additive method in § 1065.660(c)(3).

(g) CH₄. For reporting CH₄ or for demonstrating compliance with CH₄ standards, you may use a FID analyzer with a nonmethane cutter as described in § 1065.265 or you may use a GC‑FID as described in § 1065.267. Determine CH₄ as described in § 1065.660(d).

§ 1065.265 Nonmethane cutter.

(a) Application. You may use a nonmethane cutter to measure CH₄ with a FID analyzer. A nonmethane cutter oxidizes all nonmethane hydrocarbons to CO₂ and H₂O. You may use a nonmethane cutter for raw or diluted exhaust for batch or continuous sampling.

(b) System performance. Determine nonmethane‑cutter performance as described in § 1065.365 and use the results to calculate NMHC emission CH₄ or NMHC emissions in § 1065.660.

(c) Configuration. Configure the nonmethane cutter with a bypass line if it is needed for the verification described in § 1065.365.

(d) Optimization. You may optimize a nonmethane cutter to maximize the penetration of CH₄ and the oxidation of all other hydrocarbons. You may humidify a sample and you may dilute a sample with purified air or oxygen (O₂) upstream of the nonmethane cutter to optimize its performance. You must account for any sample humidification and dilution in emission calculations.

§ 1065.266 Fourier transform infrared analyzer.

(a) Application. For engines that run only on natural gas, you may use a Fourier transform infrared (FTIR) analyzer to measure nonmethane hydrocarbon (NMHC) and nonmethane‑ nonethane hydrocarbon (NMNEHC) for continuous sampling. You may use an FTIR analyzer with any gaseous‑fueled engine, including dual‑fuel and flexible‑fuel engines, to measure CH₄ and C₂H₆, for either batch or continuous sampling (for subtraction from THC).

(b) Component requirements. We recommend that you use an FTIR analyzer that meets the specifications in Table 1 of §1065.205. Note that your FTIR‑based system must meet the linearity verification in §1065.307. Use appropriate analytical procedures for interpretation of infrared spectra. For example, EPA Test Method 320 (see https://www.epa.gov/emc/method‑ 320‑vapor‑phase‑organic‑and‑inorganic‑emissions‑extractive‑ftir) and ASTM D6348 (incorporated by reference in §1065.1010) are considered valid methods for spectral interpretation. You must use heated FTIR analyzers that maintain all surfaces that are exposed to emissions at a temperature of (110 to 202) °C.

(c) Hydrocarbon species for NMHC and NMNEHC additive determination. To determine NMNEHC, measure ethene, ethyne, propane, propene, butane, formaldehyde, acetaldehyde, formic acid, and methanol. To determine NMHC, measure ethane in addition to those same hydrocarbon species. Determine NMHC and NMNEHC as described in §1065.660(b)(4) and §1065.660(c)(3).

(d) NMHC and NMNEHC CH₄ and C₂H₆ determination from subtraction of CH₄ and C₂H₆ from THC. Determine CH₄ as described in §1065.660(d)(2) and C₂H₆ as described §1065.660(e). Determine NMHC from subtraction of CH₄ from THC as described in §1065.660(b)(3) and NMNEHC from subtraction of CH₄ and C₂H₆ as described §1065.660(c)(2). Determine CH₄ as described in §1065.660(d)(2) and C₂H₆ as described §1065.660(e).

(e) Interference verification. Perform interference verification for FTIR analyzers using the procedures of §1065.366. Certain interference gases can interfere with FTIR analyzers by causing a response similar to the hydrocarbon species of interest. When running the interference verification for these analyzers, use interference gases as follows:

(1) The interference gases for CH₄ are CO₂, H₂O, and C₂H₆.

(2) The interference gases for C₂H₆ are CO₂, H₂O, and CH₄.

(3) The interference gases for other measured hydrocarbon species are CO₂, H₂O, CH₄, and C₂H₆.

§ 1065.267 Gas chromatograph.

(a) Application. You may use a gas chromatograph to measure CH₄ with a flame ionization detector (GC‑FID) to measure CH₄ and C₂H₆ concentrations of diluted exhaust for batch sampling. While you may also use a nonmethane cutter to measure CH₄, as described in § 1065.265, use a reference procedure based on a gas chromatograph for comparison with any proposed alternate measurement procedure under § 1065.10.

 (b) Component requirements. We recommend that you use a gas chromatograph that meets the specifications in Table 1 of § 1065.205, and it must also meet the linearity verification in § 1065.307. GC‑FID that meets the specifications in Table 1 of § 1065.205, and that the measurement be done according to SAE J1151 (incorporated by reference in §1065.1010). The GC‑FID must meet the linearity verification in §1065.307.

§ 1065.269   Photoacoustic analyzer for ethanol and methanol.

(a) Application. You may use a photoacoustic analyzer to measure ethanol and/or methanol concentrations in diluted exhaust for batch sampling.

(b) Component requirements. We recommend that you use a photoacoustic analyzer that meets the specifications in Table 1 of §1065.205. Note that your photoacoustic system must meet the verification in §1065.369 and it must also meet the linearity verification in §1065.307. Use an optical wheel configuration that gives analytical priority to measurement of the least stable components in the sample. Select a sample integration time of at least 5 seconds. Take into account sample chamber and sample line volumes when determining flush times for your instrument.

NO_X and N₂O Measurements

§ 1065.270 Chemiluminescent detector.

(a) Application. You may use a chemiluminescent detector (CLD) to measure NO_X concentration in raw or diluted exhaust for batch or continuous sampling. We generally accept a CLD for NO_X measurement, even though it measures only NO and NO₂, when coupled with an NO₂‑to‑NO converter, since conventional engines and aftertreatment systems do not emit significant amounts of NO_X species other than NO and NO₂. Measure other NO_X species if required by the standard‑setting part. While you may also use other instruments to measure NO_X, as described in § 1065.272, use a reference procedure based on a chemiluminescent detector for comparison with any proposed alternate measurement procedure under § 1065.10.

(b) Component requirements. We recommend that you use a CLD that meets the specifications in Table 1 of § 1065.205. Note that your CLD‑based system must meet the quench verification in § 1065.370 and it must also meet the linearity verification in § 1065.307. You may use a heated or unheated CLD, and you may use a CLD that operates at atmospheric pressure or under a vacuum. You may use a CLD that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.

(c) NO₂ ‑to‑NO converter. Place upstream of the CLD an internal or external NO₂‑to‑NO converter that meets the verification in § 1065.378. Configure the converter with a bypass line if it is needed to facilitate this verification.

(d) Humidity effects. You must maintain all CLD temperatures to prevent aqueous condensation. If you remove humidity from a sample upstream of a CLD, use one of the following configurations:

(1) Connect a CLD downstream of any dryer or chiller that is downstream of an NO₂‑to‑NO converter that meets the verification in § 1065.378.

(2) Connect a CLD downstream of any dryer or thermal chiller that meets the verification in § 1065.376.

(e) Response time. You may use a heated CLD to improve CLD response time.

§ 1065.272 Nondispersive ultraviolet analyzer.

(a) Application. You may use a nondispersive ultraviolet (NDUV) analyzer to measure NO_X concentration in raw or diluted exhaust for batch or continuous sampling. We generally accept an NDUV for NO_X measurement, even though it measures only NO and NO₂, since conventional engines and aftertreatment systems do not emit significant amounts of other NO_X species. Measure other NO_X species if required by the standard‑setting part. Note that good engineering judgment may preclude you fromusing it may not be appropriate to use an NDUV analyzer if sampled exhaust from test engines contains oil (or other contaminants) in sufficiently high concentrations to interfere with proper operation.

(b) Component requirements. We recommend that you use an NDUV analyzer that meets the specifications in Table 1 of § 1065.205. Note that your NDUV‑based system must meet the verifications in § 1065.372 and it must also meet the linearity verification in § 1065.307. You may use a NDUV analyzer that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.

(c) NO₂ ‑to‑NO converter. If your NDUV analyzer measures only NO, place upstream of the NDUV analyzer an internal or external NO₂‑to‑NO converter that meets the verification in § 1065.378. Configure the converter with a bypass to facilitate this verification.

(d) Humidity effects. You must maintain NDUV temperature to prevent aqueous condensation, unless you use one of the following configurations:

(1) Connect an NDUV downstream of any dryer or chiller that is downstream of an NO₂‑to‑NO converter that meets the verification in § 1065.378.

(2) Connect an NDUV downstream of any dryer or thermal chiller that meets the verification in § 1065.376.

§ 1065.275 N₂O measurement devices.

(a) General component requirements. We recommend that you use an analyzer that meets the specifications in Table 1 of § 1065.205. Note that your system must meet the linearity verification in § 1065.307.

(b) Instrument types. You may use any of the following analyzers to measure N₂O:

(1) Nondispersive infra‑red (NDIR) analyzer. You may use an NDIR analyzer that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias. infrared (NDIR) analyzer.

(2) Fourier transform infra‑red (FTIR) analyzer. You may use an FTIR analyzer that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias. Use appropriate analytical procedures for interpretation of infrared spectra. For example, EPA Test Method 320 is considered a valid method for spectral interpretation (see http://www.epa.gov/ttn/emc/methods/method320.html). infrared (FTIR) analyzer. Use appropriate analytical procedures for interpretation of infrared spectra. For example, EPA Test Method 320 (see §1065.266(b)) and ASTM D6348 (incorporated by reference in §1065.1010) are considered valid methods for spectral interpretation.

(3) Laser infrared analyzer. Examples of laser infrared analyzers are pulsed‑mode high‑resolution narrow band mid‑infrared analyzers, and modulated continuous wave high‑resolution narrow band mid‑infrared analyzers.

(3)(4) Photoacoustic analyzer. You may use a photoacoustic analyzer that has compensation algorithms that are functions of other gaseous measurements. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias. Use an optical wheel configuration that gives analytical priority to measurement of the least stable components in the sample. Select a sample integration time of at least 5 seconds. Take into account sample chamber and sample line volumes when determining flush times for your instrument.

(4)(5) Gas chromatograph analyzer. You may use a gas chromatograph with an electron‑capture detector (GC‑ECD) to measure N₂O concentrations of diluted exhaust for batch sampling.

(i) You may use a packed or porous layer open tubular (PLOT) column phase of suitable polarity and length to achieve adequate resolution of the N₂O peak for analysis. Examples of acceptable columns are a PLOT column consisting of bonded polystyrene‑divinylbenzene or a Porapack Q packed column. Take the column temperature profile and carrier gas selection into consideration when setting up your method to achieve adequate N₂O peak resolution.

(ii) Use good engineering judgment to zZero your instrument and correct for drift appropriately. You do not need to follow the specific procedures in § 1065.530 and § 1065.550(b) that would otherwise apply. For example, you may perform a span gas measurement before and after sample analysis without zeroing. Use the average area counts of the pre‑span and post‑span measurements to generate a response factor (area counts/span gas concentration), which you then multiply by the area counts from your sample to generate the sample concentration.

(c) Interference validation verification. Perform interference validation verification for NDIR, FTIR, laser infrared analyzers and photoacoustic analyzers using the procedures of § 1065.375. Interference validation verification is not required for GC‑ECD. Certain interference gases can positively interfere with NDIR, FTIR, and photoacoustic analyzers by causing a response similar to N₂O. When running the interference verification for these analyzers, use interference gases as follows:

(1) The interference gases for NDIR analyzers are CO, CO₂, H₂O, CH₄ and SO₂. Note that interference species, with the exception of H₂O, are dependent on the N₂O infrared absorption band chosen by the instrument manufacturer and should be determined dently for each analyzer. For each analyzer determine the N₂O infrared absorption band. For each N₂O infrared absorption band, determine the appropriate interference gases to use in the verification

(2) Use good engineering judgment to determine Determine interference gases for FTIR and laser infrared analyzers. Note that interference species, with the exception of H₂O, are dependent on the N₂O infrared absorption band chosen by the instrument manufacturer and should be determined independently for each analyzer.  For each analyzer determine the N₂O infrared absorption band. For each N₂O infrared absorption band, determine the appropriate interference gases to use in the verification.

(3) The interference gases for photoacoustic analyzers are CO, CO₂, and H₂O.

O₂ Measurements

§ 1065.280 Paramagnetic and magnetopneumatic O₂ detection analyzers.

(a) Application. You may use a paramagnetic detection (PMD) or magnetopneumatic detection (MPD) analyzer to measure O₂ concentration in raw or diluted exhaust for batch or continuous sampling. You may use O₂ measurements with intake air or fuel flow measurements to calculate exhaust flow rate according to § 1065.650.

(b) Component requirements. We recommend that you use a PMD or MPD analyzer that meets the specifications in Table 1 of § 1065.205. Note that it must meet the linearity verification in § 1065.307. You may use a PMD or MPD that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.

Air-to-Fuel Ratio Measurements

§ 1065.284 Zirconia (ZrO₂) analyzer.

(a) Application. You may use a zirconia (ZrO₂) analyzer to measure air‑to‑fuel ratio in raw exhaust for continuous sampling. You may use O₂ measurements with intake air or fuel flow measurements to calculate exhaust flow rate according to § 1065.650.

(b) Component requirements. We recommend that you use a ZrO₂ analyzer that meets the specifications in Table 1 of § 1065.205. Note that your ZrO₂‑based system must meet the linearity verification in § 1065.307. You may use a Zirconia analyzer that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.

PM Measurements

§ 1065.290 PM gravimetric balance.

(a) Application. Use a balance to weigh net PM on a sample medium for laboratory testing.

(b) Component requirements. We recommend that you use a balance that meets the specifications in Table 1 of § 1065.205. Note that your balance‑based system must meet the linearity verification in § 1065.307. If the balance uses internal calibration weights for routine spanning and the weights do not meet the specifications in § 1065.790, the weights must be verified independently with external calibration weights meeting the requirements of § 1065.790. While you may also use an inertial balance to measure PM, as described in § 1065.295, use a reference procedure based on a gravimetric balance for comparison with any proposed alternate measurement procedure under § 1065.10.

(c) Pan design. We recommend that you use a balance pan designed to minimize corner loading of the balance, as follows:

(1) Use a pan that centers the PM sample media (such as a filter) on the weighing pan. For example, use a pan in the shape of a cross that has upswept tips that center the PM sample media on the pan.

(2) Use a pan that positions the PM sample as low as possible.

(d) Balance configuration. Configure the balance for optimum settling time and stability at your location.

§ 1065.295 PM inertial balance for field-testing analysis.

(a) Application. You may use an inertial balance to quantify net PM on a sample medium for field testing.

(b) Component requirements. We recommend that you use a balance that meets the specifications in Table 1 of § 1065.205. Note that your balance‑based system must meet the linearity verification in § 1065.307. If the balance uses an internal calibration process for routine spanning and linearity verifications, the process must be NISTSI‑traceable. You may use an inertial PM balance that has compensation algorithms that are functions of other gaseous measurements and the engine's known or assumed fuel properties. The target value for any compensation algorithm is 0.0% (that is, no bias high and no bias low), regardless of the uncompensated signal's bias.

(c) Loss correction. You may use PM loss corrections to account for PM loss in the inertial balance, including the sample handling system.

(d) Deposition. You may use electrostatic deposition to collect PM as long as its collection efficiency is at least 95%.