EPA Method 21/phx42 Feature Comparison

6.1 Detector Type

 

The VOC instrument detector shall respond to the compounds being processed. Detector types potentially meeting this requirement include, but are not limited to, catalytic oxidation, flame ionization, infrared absorption, and photoionization.

phx42 uses a Flame Ionization Detector (FID).

6.2 Measurement Capability

 

The instrument shall be capable of measuring the leak definition concentration specified in the regulation.

phx42 has an range of 0–100,000 ppm.

6.3 Scale Readability

 

The scale of the instrument meter shall be readable to ±2.5 percent of the specified leak definition concentration.

phx42 displays measurements to one-tenth of 1 ppm.

6.4 Sample Flow Rate

 

The instrument shall be equipped with an electrically driven pump to ensure a sample is provided to the detector at a constant flow rate.

The nominal sample flow rate, as measured at the sample probe tip, shall be 0.10 to 3.0 L/min (0.004 to 0.1 ft³/min) when the probe is fitted with a glass wool plug or filter that may be used to prevent plugging of the instrument.

phx42 uses pump throttling to maintain a constant flow rate of 0.3L/min, regardless of probe length or partial filter obstruction.

6.5 Probe Specifications

 

The instrument shall be equipped with a probe or probe extension for sampling, not to exceed 6.4 mm (1/4 in) in outside diameter, with a single end opening for admission of sample.

phx42 uses a 0.225-inch metal probe tip.

6.6 Intrinsic Safety

 

The instrument shall be intrinsically safe for operation in explosive atmospheres as defined by the National Electrical Code by the National Fire Protection Association or other applicable regulatory code.

The instrument shall, at a minimum, be intrinsically safe for Class 1, Division 1 conditions, and/or Class 2, Division 1 conditions, as appropriate. The instrument shall not be operated with any safety device, such as an exhaust flame arrestor, removed.

phx42 is certified intrinsically safe for Class 1, Division 1, Groups A, B, C, D, with a Temperature Rating of T4. Certification documentation is available at LDARtools.com.

8.1.3.2 Response Time

 

The instrument response time shall be equal to or less than 30 seconds. The instrument pump, dilution probe (if any), sample probe, and probe filter that will be used during testing shall all be in place during the response time determination.

phx42 has an average response time of under 3.5 seconds.

8.1.1.3 Response Factors

 

Alternatively, if response factors have been published for the compounds of interest for the instrument or detector type, the response factor determination is not required, and existing results may be referenced.

Examples of published response factors for flame ionization and catalytic oxidation detectors are included in References 1–3 of Section 17.0.

Because phx42 uses an FID, currently published response factors for the other FID values can be used. A list of these FID response factors is available at LDARtools.com.