Open Path Monitoring

Providing differentiated gas detection capabilities to plants and facilities seeking to monitor harmful fugitive gases

What is Open Path Monitoring?

Gas analyzers use different techniques to monitor gases and compounds in a variety of conditions and landscapes. A common need for gas analyzers in industry is the ability to monitor gases that are released into the surrounding atmosphere as by-products of manufacturing processes (petroleum plants, etc.) These fugitive gases often escape through fencelines of a refinery and spread into neighboring communities or waterways. In order to comply with government regulation and ensure the health and safety for all persons involved, there must be a way for industry to know which gases (and in what exact concentrations) impact the surrounding environments through wind or circulation. This is where open path monitoring is useful.

Open Path Monitoring describes the way analyzers monitor the escaping gases in the air and atmosphere. This technique uses ambient air samples surrounding the facilities to identify and quantify the levels of chemicals and compounds within.

Open path systems are used along the perimeters of industrial properties, monitoring for fugitive gases crossing the boundaries of the property

How does Open Path Monitoring work?

Open path monitoring is performed by sending a beam of light through open air that is reflected back to the analyzer by a retroreflector

These analyzers don’t need to intake any air to be able to identify and quantify the chemicals. Unlike portable point analyzers or extractive CEMS systems that intake air into the instrument, an open path analyzer uses an internal radiation source (ultraviolet, visible, or infrared) to project a beam of light across the ambient air sample.

The absorption spectrum of light, unique to each gas species, is measured and recorded

This beam of light projected by an Open Path Analyzer interacts with the gaseous compounds within the air sample and, depending on the wave length, causes molecules of those gases to absorb the light and start to vibrate/rotate. Software on an open path analyzer can then use this information to ultimately translate the vibrations of the molecules into useable data. Due to principles of physics concerning electromagnetic radiation…

The monitors identify the gases by referencing Cerex’s library of light absorption fingerprints

Cerex’s advanced real-time software and the principle of the Beer-Lambert Law outputs the type and concentrations of any gases within the air samples in real-time with near complete accuracy. no intake gases combined with Cerex’s careful engineering in both equipment and software means maintenance and cost is extremely reduced.

The tradeoff for the convience of this technique is that environmental conditions (water vapor, fog, humidity) can affect the beam in which the gases are monitored. Compounds such as water vapor can absorb light at multiple wavelengths – “muddling” the data and making it hard to distinguish target gases in the overlap regions. One solution to this is considering if the environment can be made suitable for the installation. In the case of most open-path analyzers that are placed along refinery fencelines, environmental conditions can not be controlled. Thus, a more holistic solution is to use a high resolution instrument capable of monitoring spectrum regions with no overlap. Cerex’s UV SENTRY and AIR SENTRY use high resolution spectrometers to effectively overcome this challenge.

Why choose a Cerex Open Path Analyzer?

Decades of proven testing, iterations, and development

Since producing the first commercially available Open-Path FTIR remote sensing analyzer in 1994, Cerex has continued to improve it’s open-path technologies for increased reliability, accuracy, and ease of user experience. After decades of success with the AIR SENTRY, Cerex expanded its capabilities with the introduction of the UV SENTRY to target more gases previously undetectable with infrared technologies. Decades of iterations and development has led to instruments of incomparable quality and performance that Cerex is proud to provide.

Since producing the first commercially avaiable Open-Path FTIR remote sensing analyzer in 1994, Cerex has continued to improve it’s open-path technologies for increased reliability, accuracy, and ease of user experience. After decades of success with the AIR SENTRY, Cerex expanded it’s capabilties with the introudction of the UV SENTRY to target more gases previously undetectable with infrared technologies. Decades of iterations and development has led to instruments of incomparable quality and performance that Cerex is proud to provide.

Tested by the US EPA and complies with national and international government standards (TO-16, etc.)

The US EPA and government agencies have used Cerex open path analyzers to conduct studies on the efficacy of open path UV DOAS and FTIR spectroscopy systems for fenceline monitoring. Depending on which analyzer chosen, Cerex Open Path analyzers meet the following requirements

40 CFR § 63.658 USEPA Method 325 A/B
SCAQMD Rule 1180
BAAQMD Refinery Regulation 12 Rule 15
USEPA TO-16
RCER-2020

Trusted by some of world’s largest international companies

Chevron, Shell, Marathon, and numerous other refineries and international agencies trust Cerex’s Open Path Analyzers

Real-time Software

Chevron, Shell, Marathon, and numerous other refineries and international agencies trust Cerex’s Open Path Analyzers

Unmatched data presentation and access

Chevron, Shell, Marathon, and numerous other refineries and international agencies trust Cerex’s Open Path Analyzers

Customer Satisfaction and Support Guaranteed

Chevron, Shell, Marathon, and numerous other refineries and international agencies trust Cerex’s Open Path Analyzers

Open Path and Fenceline Analyzers

Monitor fugitive gases up to 1km around the fence line of your facility with cost-effective UV-DOAS and FTIR analyzers

UV Sentry Series

 

Best open-path detection limits for Benzene & VOCs
Refinery Fence-line Air Monitoring

EPA Method 325

Air Sentry

Hundreds of detectable gases
Refinery Fence-line Air Monitoring
Rule 1180

UV Sentry Series