VICI Model 235 Dynacalibrator® Dynamic Calibration Gas Generator

Overview

The VICI Model 235 Dynacalibrator® is a precision-engineered dynamic calibration gas generator designed for trace-level gas standard generation in analytical laboratories, environmental monitoring facilities, and industrial emissions testing environments. It operates on the well-established principle of temperature-controlled permeation, where volatile organic compounds (VOCs) or other calibration standards are released from certified permeation tubes at a stable, predictable rate governed by Arrhenius kinetics. By maintaining the permeation tube within a thermally stabilized chamber (±0.01°C at 110°C), the instrument delivers highly reproducible output concentrations ranging from sub-ppb to high-ppm levels—enabling quantitative calibration of gas chromatographs (GC), photoionization detectors (PID), flame ionization detectors (FID), and continuous emission monitoring systems (CEMS). Its dual-mass-flow-controller architecture separates carrier gas delivery from dilution gas control, ensuring stoichiometric mixing fidelity and minimizing concentration drift due to pressure or temperature fluctuations.

Key Features

• Dual independent mass flow controllers (MFCs): one for carrier gas (e.g., nitrogen or zero air), one for dilution gas—both calibrated to NIST-traceable standards
• High-stability permeation oven with PID-controlled heating and real-time thermal monitoring; temperature range: 30°C to 110°C (or ambient +2°C minimum)
• Touchscreen HMI interface for intuitive setpoint configuration, real-time parameter display, and system diagnostics
• Integrated permeation chamber with optimized laminar flow geometry to ensure uniform thermal distribution and minimize boundary-layer effects
• Modular design supporting interchangeable permeation tubes (standard 1/4″ OD format) with documented permeation rates and expiration dates per US EPA Method TO-15 and ASTM D6196
• Robust stainless-steel and electropolished wetted path components compliant with ISO 8573-1 Class 1 for particle and hydrocarbon contamination control

Sample Compatibility & Compliance

The Model 235 supports a broad spectrum of volatile and semi-volatile calibration standards—including benzene, toluene, formaldehyde, sulfur dioxide, nitrogen oxides, and halogenated hydrocarbons—provided as NIST-certified permeation tubes from accredited suppliers (e.g., AccuStandard, Restek, VICI Journeys). Each tube must be validated for use within its specified temperature window and shelf life. The system meets functional requirements outlined in US EPA Methods 205.1, 205.2, and 205.3 for dynamic dilution calibration, and aligns with ISO/IEC 17025:2017 clause 7.7 on reference material traceability. When operated under documented SOPs, it supports GLP and GMP audit readiness, including full electronic record retention for temperature logs, flow readings, and operational timestamps.

Software & Data Management

While the Model 235 operates autonomously via its embedded microcontroller and touchscreen interface, optional RS-232 or analog 4–20 mA outputs enable integration into laboratory information management systems (LIMS) or SCADA platforms. All critical parameters—including oven temperature, carrier and diluent flow rates, and runtime—are timestamped and stored locally for ≥30 days. For regulated environments, optional firmware upgrades support 21 CFR Part 11-compliant user authentication, electronic signatures, and immutable audit trails when paired with validated third-party data acquisition software.

Applications

• Primary calibration of gas analyzers used in ambient air quality networks (e.g., EPA SLAMS, EEA AirBase)
• Verification and span calibration of portable VOC monitors deployed in industrial hygiene surveys
• Method validation and ongoing quality assurance for ASTM D5466, ISO 16017-1, and EN 14662 compliance testing
• Generation of multi-component gas standards via sequential or parallel permeation tube configurations
• Supporting research-grade studies requiring precise, time-resolved exposure profiles in inhalation toxicology chambers

FAQ

What types of permeation tubes are compatible with the Model 235?
The instrument accepts standard 1/4-inch outer diameter permeation tubes supplied by NIST-accredited vendors. Tube compatibility depends on chemical stability at elevated temperatures and manufacturer-specified operating ranges.
Does the Model 235 require external gas supplies?
Yes—it requires two independently regulated, oil-free, and hydrocarbon-free gas sources: one for carrier gas (typically zero air or nitrogen) and one for dilution gas (same or different composition). Pressure regulation and filtration upstream of the MFCs are strongly recommended.
Can the Model 235 generate multi-gas mixtures?
Not natively—but it can be integrated with multi-position permeation tube ovens or used sequentially with manual tube swaps to produce discrete single-analyte standards required for multi-point calibration curves.
Is temperature calibration traceable to national standards?
The internal PT100 sensor is factory-calibrated against NIST-traceable references; users may perform periodic verification using a calibrated external thermometer probe inserted into the designated oven port.
What maintenance is required for long-term accuracy?
Annual verification of MFC linearity and oven temperature uniformity is recommended. Permeation tubes must be replaced before expiration, and the permeation chamber should be inspected quarterly for particulate accumulation or seal integrity.