How to choose the right type of gas detection

The first step is to identify and define the risks. Every company is obliged to carry out a risk assessment to identify potential hazards. These include gas-related risks.

A gas is a swarm of molecules that moves randomly and chaotically, colliding with each other and with their surroundings. The most obvious example is the air around us, which is made up of different gas molecules. Gases are therefore ubiquitous and present numerous dangers. They are classified into 3 risk categories:

• The risk of fire and/or explosion, such as the presence of flammable gases (methane, butane, propane ...)
• The risk of poisoning/intoxication such as a leak of one or more toxic gases (carbon monoxide, hydrogen sulfide, carbon dioxide, chlorine...)
• The risk of anoxia/hypoperoxia, such as a deficiency or too high a concentration of oxygen (The oxygen can be consumed or displaced by another gas).

If one of these hazards is identified, then the gas detection is a means of reducing these risks.

The second stage in the acquisition of gas detection equipment is to identify the objective. Once this has been defined, it will enable you to choose the best solution. There are many different reasons for purchasing gas detection equipment:

• Obtain management reports for a site manager (remote or off-site alarm notifications, event data, etc.)
• Comply with regulations on the legal side
• Respect the specific conditions imposed by insurers

Whatever the primary objective, it's important to remember that a gas detection solution is there to protect human life. The motivation - be it legal, for insurers or site managers - helps define the type of fixed or portable gas detection, as well as the functionalities and features to meet the objective.

Questions to ask yourself ? Here they are : 

• What gases are to be detected and where do they come from?
• Where and under what environmental conditions will the detection system be used?
• How easy is it to use for operators and routine maintenance personnel?

The answers to these questions have a direct impact on the proposed solution, associated costs and equipment maintenance.

A suitable gas detection solution must detect the presence of a particular gas and trigger an alarm before dangerous levels of concentration are reached.
It's important to remember that the identification of all potential hazards is the responsibility of the end-user, and it's the risk assessment that identifies the gases to be detected.
Here are the steps involved :

STEP 1
Identify the type of risk you face (flammable, toxic and/or asphyxiant) to determine the type of sensor to use.

STEP 2
Determining the relative levels of concentration which may prove dangerous enables alarm thresholds to be defined, and the position of the sensor in the case of fixed gas detection, etc.

STEP 3
Identifying potential sources of gas leaks helps determine the number and location of sensors required for a fixed gas detection system. On the other hand, if leak sources are unknown, portable gas detection equipment is preferred.

Common sources of gas emissions include:

• Natural emissions such as methane and hydrogen sulfide from waste decomposition
• Leaks from a supply pipe or storage tank, such as a natural gas pipeline.
• Emissions from combustion processes, such as carbon monoxide from exhausts or boiler flue pipes
• Emissions from combustion processes such as solvents in the printing and coatings industry
• Emissions from a production plant, such as ammonia from a refrigeration plant or nitrogen from a nitrogen production plant.

Gas detectors are equipped with sensors that are sensitive to environmental conditions. This can affect performance, accuracy and reliability. Temperature, humidity and pressure levels on site therefore have a direct influence on the type of equipment to choose.

Other factors such as potential variations resulting from the production process itself, diurnal and nocturnal fluctuations or seasonal variability can also influence the type of equipment that will be appropriate.

STEP 1
Determine whether the equipment will be used indoors or outdoors:

• Outdoors, the detector will be exposed to wind, rain or salt spray. It must be able to withstand the corrosive effects of such an environment.
• Indoors, less robust housings are sufficient, but exposure to water (water jets for washing) or dust (dirt) must be defined.

STEP 2
Define whether there are environmental conditions other than climatic conditions that could influence the choice of a type of equipment.

For example:

• Hydrogen sulfide has corrosive properties, and other atmospheric compounds can adversely affect the reliability of certain detection technologies.
• Silicone-based substances with inhibiting properties on catalytic filament detection technologies.

STEP 3
Define the level of safety required for this equipment in certain hazardous areas. Depending on the zone, you need to choose a device with the appropriate ATEX certification (Zone O: Ex 1G ..., Zone 1: Ex 2G, Zone 2: Ex 3G..., etc ....).

It's essential to take a holistic approach when considering equipment features. There are significant variations between products, and the more features there are, the higher the cost.

Here are a few examples that offer the user additional benefits and make one product more suitable than another :

• display of local units of measure
• the presence of a local user interface
• software compatibility
• the number of relays and outputs required
• remote sensor connection options
• integrated diagnostic functions
• hot swapping of cartridges
• event logging capabilities
• ...

Ease of use :

The stakes are high, because it's not enough to install gas detection equipment to comply with legislation, standards or insurance demands. The aim is to protect operators: a gas detector that is easy to handle will be easier for operators to use.

Simple maintenance :

Downtime of detection equipment can lead to a drop in production. That's why it's essential to choose solutions that enable sensors to be replaced quickly, easily and safely.

The choice of gas detection technology is another important factor, as it has an impact on maintenance, for example in the case of a cell for measuring the risk of explosion :

• Catalytic filaments: they do not ensure fail-safe operation and require frequent maintenance.
• Infrared: reduces the number of routine maintenance operations, but at a higher purchase price.