Cerex FTIR

PPM to PPB level monitoring of criteria gases in a versatile enclosure

The Cerex FTIR is one of the newest additions to our line of multi-gas point analyzers and achieves a middle ground between the extreme sensitivity of the Cerex Shepherd and the smaller size of the Micro FTIR.

The Cerex FTIR is recommended for a lower cost, lower maintenance FTIR option and is offered in three optimized variations: general monitoring of hazardous gases, hospital and waste anesthetic gas monitoring (WAG), and continuous emissions monitoring (CEM). All three use a low cost, zero maintenance, high resolution DTGS detector and precision spectrometer.


  • Significantly higher spectral resolution and performance than similarly priced FTIR products
  • Preconfigured gas detection libraries for multiple applications, quickly switch libraries as needed for specific applications
  • No need for routine calibration – no “span” and “zero” required
  • Minimal consumables: IR Source and filters are low cost, long life, and fast to swap/replace
  • Continuous operation on AC power or four hours operation on single battery charge (optional)
  • An integrated Windows 10/11 PC allows for full networking of the analyzer, which includes:
    • Touchscreen interface, audible and visual alarms
    • Redundant data storage to network attached storage.
    • Data telemetry via MODBUS TCP/IP or Serial.
    • Full remote control via VNC
    • Programmable emailing of data and alarms

Pictured: Cerex FTIR / Cerex WAG in portable configuration


Recommended for ambient air monitoring applications, waste anesthetic monitoring, anesthetic leak detection, and hospital workplace exposure monitoring.

General Specifications
Weight 55 lbs (25kg)
Measurements 68.75cm x 29.43cm x 29.69cm
(27.07in x 11.59in x 11.69in)
Enclosure Aluminum, rack mountable, bench top & upright rolling operating positions
Power 120VAC / 50-60Hz or 240VAC / 50-60Hz
Operating Temperature Temperature controlled general purpose atmosphere 0C°- 40C°
Operating Humidity Up to 75%
Cell Optical Path Length  10 meters
IR Source 1 year, field serviceable; typical 3 to 5 years
Sample Filter
Dependent on application – replace as necessary

Pictured: Cerex FTIR CEM in rackmount or bench top configuration


Recommended for extractive continuous emissions monitoring 


General Specifications  
Weight 55 lbs (25kg)
Measurements 68.75cm x 29.43cm x 29.69cm
(27.07in x 11.59in x 11.69in)
Enclosure Aluminum, rack mountable, bench top & upright rolling operating positions
Power 120VAC / 50-60Hz or 240VAC / 50-60Hz
Operating Temperature

Temperature controlled general purpose atmosphere 0C°- 40C°

Operating Humidity Up to 75%
Optical Path Length  1cm to 10m
IR Source 1 year, field serviceable; typical 3 to 5 years
Sample Filter
Dependent on application – replace as necessary

How it Works

Portable Point FTIR Technology

The FTIR Process

The Cerex FTIR uses advanced multi-gas technology to monitor concentrations of multiple gases. Regardless of application, sample gases are pumped into the analyzer through a sample hose or attachment.
Next, as the sample flows through the optical cell, an infrared light interacts in a unique way with each gas in the mixture.

Real Time Results

Cerex’s advanced software is then able to detect the presence of any user-selected gas – and calculate the concentration – all in a matter of seconds. Cerex’s software can also be configured to detect and identify unknown gases.

The result of coupling our proven FTIR detection system and real time analytic software is an industry leading FTIR multi-gas analyzer.

Great sensitivity and good cost-effective solution for detecting toxic gases in ambient air

Offering real time quantification of multiple compounds ranging from parts-per-million to parts-per-billion detection limits, the Cerex FTIR provides deep analysis
compromising on price.

Our most “hands-off” FTIR analyzer yet – no maintenance required

With almost no moving parts, the Cerex FTIR is capable of continuously monitoring for long periods of time without regular inspection. This capability saves precious time, money, and resources.

Individual species of prolific hazardous air pollutants

The Cerex FTIR is offered fully configured to meet the requirements of your air quality monitoring application. Choose up to 50 target gases to monitor simultaneously from a Cerex reference library of 385 compounds and more.

Common Detectable Gases

Extensive Library with Options for Customization

Cerex has over 385 compounds available for detection with the Cerex FTIR. If your compound is not one of the compounds already available within our database, the Cerex FTIR may import gas spectra from the numerous FTIR databases on the web (NIST, EPA, PNNL, etc.)

If you have a compound that is not available in a public database, we may be able to work with you to develop a custom spectrum. Detection limits are a function of the IR detector, installed path length, and site conditions. The detection limits shown have been empirically determined from bump tests of fielded instruments at full path-length.

It is efficient as an alarm and easily integrated into your existing alarm system.

*NOTE: If desired target gases are available within the UV spectrum, we recommend the Cerex HOUND SERIES for better pricing options. The UV Hound is an open-path analyzer that uses UV-DOAS (Ultra Violet Differential Optical Absorption Spectroscopy). Find more information about UV-DOAS and FTIR techniques here.

Cerex FTIR Common Target Gases

Acetaldehyde (C2H4O)
Acetic Acid (C2H4O2)
Acetone (CH3COCH3)
Acetylene (C2H2)
Acrolein (C3H4O)
Benzaldehyde (C7H6O)
Butane (C4H10)
n-Butyl (C6H12O2)
Carbon Dioxide (CO2)
Carbon Monoxide (CO)
Chlorine Dioxide (ClO2)
Ethane (C2H6)
Ethanol (C2H6O)
Formaldehyde (CH2O)
Formic Acid (CH2O2)
n-Hexane (C6H14)
Hydrogen Bromide (HBr)
Hydrogen Chloride (HCl)
Hydrogen Fluoride (HF)
Methane (CH4)
Nitric Oxide (NO)
Nitrogen Dioxide (N2O)
Phenol (C6H5OH)
Phosgene (CCl2O)
Water Vapor (H2O)


Results You Can Rely On

Cerex recognizes that detailed gas monitoring results need to be reliable and available quickly to various stakeholders. For this reason, Cerex engineers developed software to accurately detect and display gases within the air in real time from any location.

On a Cerex FTIR, a user can see results not only on the analyzer's touchscreen interface, but also remotely on a phone, tablet, or computer anywhere in the world via a virtual connection. GPS and cellular configurations make this possible in remote environments.

All data is automatically saved in an easy to access .csv file; this feature helps our clients in various ways - from daily use to crucial events such as evidence in court. Early detection translates into quicker response times, reduced environmental impact, decreased plant downtime, and reduced exposure to site personnel and the community.

Learn more about the benefits of our proprietary analysis software here.

Real time spectral subtraction and synthetic background implementation allow the Cerex FTIR to clearly display accurate concentrations of target gases over 1000 meters without interference from other gas species


Hundreds of reliable FTIR installations

Since being one of the first companies to manufacture a commercial open-path FTIR multi-gas analyzer more than two decades ago, Cerex has continued to innovate solutions and create custom visible spectrophotometry equipment.

The Cerex FTIR, a mid-tier portable point FTIR analyzer, is highly recommended for applications involving a moderate budget whilst benefitting from great sensitivity and portability. A flexible analyzer, the Cerex FTIR may be rapidly converted from portable point mode to a CEMS configuration.

All Applications

General ambient air monitoring

Workplace exposure monitoring

Waste anesthetic gas monitoring

Anesthetic leak detection

Hospital workspace exposure monitoring

Continuous Emissions Monitoring and process control monitoring

Regulation Compliance

USEPA Method 318
Extractive FTIR Method for Measurement of Emissions from Mineral Wool and Wool Fiberglass Industries

USEPA Performance Specification 15
Extractive FTIR CEMS in Stationary Sources

USEPA Method 320
Vapor Phase Organic and Inorganic Emissions by FTIR

USEPA Method 321
Determination of HCl for Portland Cement Industries

NIOSH Method 3800
Organic and Inorganic Gases by Extractive FTIR Spectrometry

ASTM Method D6348-03
Determination of Gaseous Compounds by Extractive Direct Interface Fourier Transform Infrared Spectroscopy

View current installations of our FTIR analyzers on our portfolio page

Cerex FTIR Specifications

General Parameters
Part Number Shepherd FTIR
Analyzer Type Multi-gas portable point analyzer
Technology Fourier Transform InfraRed (FTIR) Differential Optical Absorption Spectroscopy (DOAS)
Performance Available with standard HAP (385 compound & 62 Compound), Criteria, Hospital and custom gas detection libraries.
Data Output Rate User selectable from 5 seconds and up
Typical output rates are 30s, 60s, 120s, or 300s
Time weighted average available for user defined periods (8 hour, 12 hour, 24 hour)
Measurement Principle Beer-Lambert Law
Measurement Technique Classical Least Squares (CLS) regression analysis; optional Partial Least Squares (PLS)
Operating Temperature 0°C to 35°C (Optional Air Cooled Model)


Storage Temperature -40C° to 60C°
Power Supply 100 to 130V or 200 to 240VAC/50-60Hz
Power Consumption 240W MAX
Instrument Cooling Air Cooled
Installation Fixed mount or tripod mount (open path analyzer mode)
Bench-top (point analyzer mode)
Dimensions 42.1" x 21.9" x 23.3" (107cm x 55.7cm x 59.1cm)
Weight 85 lbs (38.6Kg)
Measuring Parameters
Concentration measurement accuracy ±5 % Reading TYP
Concentration measurement precision ±5 % Reading TYP
Interferent Mitigation Real time spectral subtraction and residual subtraction, multi-peak analysis.
Zero point calibration Simultaneous dual mode natural zero and/or synthetic zero on gas by gas basis. Automated compound specific background selection.
Real Time Operating Software Cerex Continuous Monitoring Software (CMS)
Operating System Windows 10 Pro
Post Collection Analysis Software Cerex Data Processor
Operating System Windows 7, 8, 10
Apodized Resolution User selectable: 0.5 cm-1, 1 cm-1, 2 cm-1, 4 cm-1, 8 cm-1, 16 cm-1, 32 cm-1
Scan frequency 6 scans/s @ 32 cm-1
Detector Stirling Cooled MCT (standard)
TE Cooled MCT (application dependent)
Detector temperature 77 K (Stirling cooled MCT)
Source SiC, 1550K
Beamsplitter ZnSe (standard)
Window material ZnSe (standard)
Wavenumber range 600-4200 cm-1 
Temperature stability < 1% per C⁰
Frequency repeatability  < 0.001 cm-1 @ 1918cm-1
Frequency accuracy < 0.06 cm-1 @ 1918cm-1
Short term stability < 0.09%
Maximum signal to noise ratio 50,000: 1 (RMS, 60s, 4 cm-1, at peak response)
Signal sampling 24-bit ADC
Quality Assurance Hardware
Type Internal linear multi-pass cell permanently mounted in beam path. External window removable.
Calibration gas inlet Quick Connect QA Adapter: 1/4" Swagelok
Calibration gas outlet Screw-in Exhaust Adapter: 3/8" Swagelok
Path Length 19.2 m
Volume 3.4 L
Maximum sample pressure 1 PSI
Pressure and temperature measurement Integrated pressure and temperature sensor
HMI Touchscreen (standard model)
Digital Interface RJ45 Ethernet LAN Port for local or internet based remote data and access using MODBUS TCP, VNC, and remote desktop.  Spectral data may be stored locally, on a NAS, or disabled. Industrial external wireless option available. Type A USB for data retrieval and peripheral accessories.
Power Connection Environmentally sealed circular Amphenol bayonet connector.
Integrated Computer Embedded industrial PC
Integrated Wind Mapping Three dimesnional ultrasonic anemometer with temperature measurement. Data integrated into CMS data tables and available via MODBUS.
Integrated Data Acqusition External ports with data integration for particulate or ancillary co-located analyzers (TDLAS laser, electrochemical, etc.).
Data Output MODBUS over RS-232, RS-485.  MODBUS over TCP-IP is standard.
Analog Output 8 channel configurable 0-24mA (4-20mA with extended range)


Cerex FTIR DTGS Standard Model Brochure (PDF 1.4MB)
(Coming Soon) Technical Sheet - Specifications (PDF)

Cerex FTIR DTGS Standard Model Brochure (PDF 1.4MB)
(Coming Soon) Technical Sheet - Specifications (PDF)

Discuss your project with our application specialists

Our engineers have decades of experience in creating custom solutions to meet your monitoring challenges