Are your gas detectors suitable for the job?

Are your gas detectors suitable for the job?

Since every work site is unique and can present different safety challenges, it is important to identify and assess risks at each of your company’s locations – then select the best gas detection technology to mitigate those risks. ALAN LEWIS, managing member of Trigas Agencies, provides a step-by-step guide.

Combustible gases fall into one of three categories: hydrocarbon gases, hydrogen gas and other combustible gases.

Hydrocarbon compounds, such as methane, butane, benzene and propane, are the combustible gases that can be the most problematic at worksites.

These organic chemical compounds only contain the elements of carbon and hydrogen. When one of these compounds mixes with the right amount of oxygen, at a certain temperature, the heat breaks apart the hydrocarbon bonds. The result is carbon dioxide and water, with energy being released through heat.

A similar reaction occurs with hydrogen. However, because there are no carbon atoms involved, the reaction only produces water and heat.

Other combustible gases that pose worksite threats are typically more dangerous because of their toxicity, rather than their flammability, although both issues can occur with these gases. Using hydrogen sulphide, as an example, toxicity is reached at 100 parts per million while the gas doesn’t become combustible until it reaches 40 000 parts per million.

Comparing the types of combustible gas detectors

It may seem redundant when a company includes various types of detectors into their gas monitoring programmes, but it does provide reliability. The different types of monitors are:

Fixed detection monitors: These play a key role in locations where an ongoing risk of combustible gas presence exists, serving as the first line of defence. Permanent sensors are strategically located to provide early warnings, operating continually as they are hardwired into the facility’s electrical system.

Fixed detection monitors can also communicate with other facility systems to automate crucial procedures involved in worker evacuations and equipment shutdowns. There are, however, some facilities that are using “temporary” area monitors as more permanent solutions, because of their multi-gas capabilities and other options giving added flexibility.

Area gas monitors: Not all worksites are suitable for fixed detection monitors – one example is confined space entry, which has a different set of requirements. In these situations, area monitors are typically recommended. They provide the early warning benefits of fixed devices in a way that’s independent of overall site infrastructure, but they can also be easily moved and redeployed to another location that requires them. Area monitors are also used in temporary situations or when there is an emergency response.

Personal gas detection: Personal gas monitors are portable devices that workers wear to detect the presence of gases in their breathing zone. This is the last line of defence against gas exposure and, when a combustible gas reaches a predefined level, workers will be warned to evacuate.

Modern combustible gas detector technology

The threat of explosion from flammable gases and vapours can cause severe injuries or death. If the potential for a flammable gas leak is present on your worksite, you need to understand your options for a combustible gas detection system. Today, there are three different types of sensors in use.

Catalytic bead (pellistor) sensors: Dr Oliver Johnson developed the catalytic combustion sensor in the 1920s at Standard Oil Company (now Chevron). This type of sensor uses beads, also called pellet-resistors or pellistors, and historically has been the most common technology used for combustible gas detection.

Non-dispersive infrared (NDIR) sensors: About 50 years later, Kozo Ishida filed a patent for the infrared gas detection system. Although advancements have taken place with this type of system over the past few decades, the foundational principle remains the same. Ishida developed a way to shine infrared light at a specific wavelength through a gas sample. If hydrocarbon gases are present, the returning wavelength will be weaker because the gases absorb infrared light.

Molecular property spectrometer (MPS) sensors: Last year saw the first revolutionary advancement in multi-gas detector technology in decades – the MPS sensor. Although the pellistor and NDIR sensors are still in wide use, this brand-new technology takes gas detection in the workplace to an entirely different level.

MPS technology is changing the gas detection industry due to:
• Accurate detection of multiple flammable gases, reducing costly false alarms;
• Being immune to poisoning (including sensor poisoning from exposure to silicones);
• No need for recalibration; and
• Automatic compensation for environmental conditions.

MPS sensors can accomplish all this with many of the most common combustible gases, including hydrogen, methane, ethane, propane, butane, pentane, hexane, toluene, xylene, ethylene, propylene and isopropanol.

This multi-combustible gas sensor can classify gases by molecular weight and density, with six possible classifications – hydrogen, hydrogen-containing mixtures and natural gas, as well as light, medium or heavy gases/mixtures. When this data is used in combination with location-enabled connected devices, a company can have high visibility into the types, locations and frequency of flammable gases being encountered by employees at a worksite.

Where can I get it?

Blackline Safety’s G7 line of safety wearables has MPS sensors as standard, which is why Trigas Agencies offers their products and works closely with the company to reach the shared vision of transforming the industrial workplace through connected safety technology. We want to ensure that every worker has the confidence to get the job done and return home safely.

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