Nitrogen Oxide Calibrator Model 408

Overview

The Model 408 Nitrogen Oxide (NO) Calibrator is a portable, NIST-traceable primary standard generator designed for field and laboratory calibration of chemiluminescence, electrochemical, and optical NO analyzers used in ambient air quality monitoring networks. It operates on the principle of controlled photolytic generation: gaseous nitrogen dioxide (NO₂) is exposed to 185 nm ultraviolet light within a quartz reaction cell, inducing photodissociation to produce stoichiometric NO in synthetic zero air or filtered ambient air. This method eliminates reliance on compressed gas cylinders and ensures traceable, stable output without chemical decomposition or adsorption artifacts. The calibrator delivers precisely defined NO mixing ratios from 0 to 1,000 ppb at a total volumetric flow rate of 3.0 L/min, with concentration accuracy of ±3 ppb or ±3% of reading—whichever is greater—across its full range. Its design enables direct integration into analyzer inlet streams, supporting both single-point verification and multi-point calibration protocols required under EPA Methods IO-3, IO-4, and ISO 13964.

Key Features

• Photolytic NO generation via 185 nm UV lamp and calibrated NO₂ permeation source—no consumable gases or catalytic converters required
• Real-time environmental compensation: automatic correction for ambient temperature, pressure, and relative humidity to maintain mixing ratio integrity
• Integrated flow control system ensuring stable 3.0 L/min total output with <30-second 95% response time to setpoint changes
• RS232 serial interface for remote diagnostics, firmware updates, and automated calibration logging compatible with LIMS and SCADA systems
• Portable form factor (24.1 × 21.6 × 9.4 cm; 2.4 kg) with dual-power capability: 12 V DC (battery or vehicle) or universal 120/240 V AC input (21 W)
• Factory-calibrated against NIST-traceable NO standards; user-accessible calibration memory allows storage of up to three independent transfer standards for field recalibration without external reference equipment

Sample Compatibility & Compliance

The Model 408 is engineered to deliver calibration gas with matched humidity content—i.e., the generated NO/air mixture retains the same relative humidity as the sampled ambient air—minimizing condensation-related errors in humid-sensitive detectors such as CLD and tunable diode laser analyzers. It complies with key regulatory and quality assurance frameworks including EPA PS-1 and PS-2 performance specifications for calibration gases, ISO/IEC 17025 requirements for reference material producers, and supports GLP/GMP audit trails when paired with compliant data acquisition software. All internal wetted surfaces are electropolished stainless steel and PTFE-lined to prevent NO adsorption or surface oxidation, ensuring long-term stability and reproducibility across repeated use cycles.

Software & Data Management

Diagnostic data—including lamp intensity, flow sensor readings, temperature/pressure/humidity values, and real-time concentration output—is accessible via RS232 using ASCII command protocol. Optional PC-based configuration utility enables parameter logging, calibration history archiving, and generation of PDF-formatted calibration certificates compliant with ISO/IEC 17025 Clause 7.7. Audit trail functionality records operator ID, timestamp, and all configuration changes, satisfying FDA 21 CFR Part 11 electronic record requirements when deployed in regulated environmental laboratories. Firmware supports over-the-air updates and configurable alarm thresholds for out-of-spec conditions (e.g., lamp degradation >15%, flow deviation >5%).

Applications

• Primary calibration of ambient NO monitors in regulatory air quality networks (e.g., U.S. EPA AQS, EU Air Quality Directive monitoring stations)
• Field validation and drift correction of mobile monitoring platforms and low-cost sensor arrays
• Reference standard transfer between central calibration labs and remote monitoring sites
• Method validation studies requiring dynamic, traceable NO standards per ASTM D6522 and EN 14625
• Quality assurance/quality control (QA/QC) programs for continuous emission monitoring systems (CEMS) in industrial stack testing

FAQ

Is the Model 408 certified for use in U.S. EPA-compliant monitoring programs?

Yes—the instrument meets the technical criteria for primary calibration sources outlined in EPA Guidance Document QA/G-5 and is routinely deployed in State Implementation Plan (SIP)-approved ambient monitoring networks.
Can it generate zero air without NO?

Yes—selecting “0 ppb” mode bypasses the NO₂ photolysis path and delivers purified zero air at 3.0 L/min with hydrocarbon content <0.1 ppm and NOₓ <50 ppt.
What maintenance is required for long-term accuracy?

The UV lamp requires replacement every 12 months or after 8,000 hours of operation; NO₂ permeation source is rated for 18 months. Both components are user-replaceable with factory-supplied kits and require no recalibration post-installation.
Does it support automated calibration sequences?

When connected to a programmable controller or analyzer with digital I/O, the RS232 interface allows full remote control of concentration steps, dwell times, and pass/fail evaluation per predefined QA protocols.
How is traceability maintained during field use?

Each unit ships with a NIST-traceable calibration certificate. Users may perform in-field verification using stored transfer standards, and all calibration events—including date, operator, and deviation values—are logged internally and exportable via RS232.