Gas Detection - Everything You Need to Know

The air we breathe is, generally speaking, comprised of 78% nitrogen, 21% oxygen and 1% other gases. However, this 1% can include a wide variety of different substances, some of which are flammable, toxic or otherwise dangerous to human health. Although they are only present in very small concentrations in the ambient air, they can quickly build up to dangerous concentrations in indoor locations, especially in enclosed or confined spaces.

For that reason, gas detection is extremely important in a wide range of locations, but especially ones where such gases are likely to be produced or accumulate. Indeed, in industrial or commercial settings, there is likely a legal responsibility on the owner or manager of the site to ensure that adequate monitoring systems are in place so as to safeguard employees and civilians in the surrounding area and minimise the chance of accident or injury.

In this introductory article, we’ll cover the basics of gas detection, including the reasons why it’s so important, the main gases that are usually detected and some of the most common locations where gas detection protocols are in place. However, there are a variety of factors which affect which sensor is most appropriate for a given situation and ensuring that the correct gas detector is installed is a serious responsibility. As such, the information in this article should never be used as a substitute for the advice of a trained and experienced professional.

Why is gas detection important?

There are three main reasons why monitoring gas concentrations is important. Firstly, some gases are toxic to human, animal and environmental health and can cause serious damage and even death when they reach certain concentrations. Secondly, many gaseous substances are highly flammable and, if exposed to a naked flame, can result in fire or explosion. Thirdly, gases which are neither toxic nor flammable can still endanger health due to their displacement of oxygen and thus their asphyxiation of the individual in question.

For those reasons, it’s imperative that gas sensors are placed strategically throughout a potentially affected building or worksite, so as to safeguard health and prevent accident or injury as far as possible. Doing so will also comply with rigorous health and safety legislation that is now present in most parts of the world. Indeed, the increasing stringency of regulations around the globe mean that the gas detection market is expected to swell from $3.4 billion in 2015 to $5.6 billion in 2024.

Aside from the safety and legal reasons for installing gas detectors, they’re also essential for optimizing the efficient of a manufacturing plant, processing facility or other industrial site as much as possible. By detecting gas leaks early, site owners can address them in a timely manner and reduce wastage, downtime and unnecessary costs.

Which gases are most commonly detected?

Depending on the location in question and the activities that are conducted there, there is a virtually limitless range of gases which may require monitoring. However, perhaps the four most commonly detected gas across a wide range of industries and applications are oxygen (O2), carbon monoxide (CO), hydrogen sulphide (H2S) and methane (CH4).

Having enough oxygen in any environment is important for obvious reasons. In the atmosphere, oxygen is present at concentrations of around 21%. If it drops below 19.5%, it becomes a cause for concern as there is insufficient O2 for a person to breathe comfortably. Oxygen levels can become quickly depleted in a poorly-ventilated area via combustion or the simple act of breathing, while other gases can displace oxygen, too. Meanwhile, concentrations above 23.5% are also unsafe for human exposure and can cause cognitive difficulties and discomfort, as well as being a fire risk.

Carbon monoxide is a milder threat than oxygen but can also cause asphyxiation in high concentrations and because it is odourless and transparent, can accumulate quickly without anyone realising. Hydrogen sulphide is both toxic and explosive and is a by-product of the decomposition of organic matter. It is often called the “rotting egg gas” due to its distinctive unpleasant smell. Methane is non-toxic but highly combustible and can quickly displace oxygen. What’s more, it’s present in all four alchemical elements and is a potent greenhouse gas which contributes strongly to global warming.

What other types of gas detection are important?

Aside from these four main gases, there are a variety of other substances which may require detection depending on the site in question. Benzene (C6H6), carbon dioxide (CO2), nitrogen oxides (NOx), ozone (O3) and hydrogen cyanide (HCN) are also commonly observed at industrial locations to ensure that they do not exceed safe thresholds.

Meanwhile, detection of refrigerants is also important in any location where cooling, freezing or air-conditioning technologies are in place. That’s because some refrigerants are extremely dangerous to human health, while others can cause significant damage to the environment. Of course, leakages of refrigerants are also highly inefficient and can cost the owner of the system a sizable expense in both the short term and long term. As such, it behoves all concerned parties – from cold storage unit owners to supermarket chain managers to private citizens – to ensure that they do not allow refrigerants to leak undetected.

Where are gas detectors used?

As mentioned above, there is a virtually unlimited array of places where gas detectors can be deployed and applications to which they can be put. However, certain industries call for more robust gas detection protocols than others and as such, are more common locations for gas detectors to be installed.

One prime example is oil rigs, refineries and other processing plants. Because these locations deal with a variety of gases on a daily basis, they must ensure that they have a comprehensive overview of the concentrations of various different substances in and around the site, as well as at its perimeter. For that reason, a far-reaching network of fixed gas detectors (including fence line monitoring sensors) is extremely important.

Other sites where gas detection is commonly observed include iron and steel production plants, chemical and petrochemical processing facilities, landfills, water and wastewater treatment centres and natural gas sourcing locations. However, gas detectors can also play an invaluable role in private businesses (such as restaurants, offices and shops), as well as homes, too.

What are the different types of gas detectors?

Depending on the specific gas that is being measured and the parameters of the environment in which it is found, there are a wide variety of different gas detectors. Generally speaking, these fall into two broad categories of fixed gas detectors and portable gas detectors.

The former are excellent for maintaining a constant overview of the ambient composition of gases in a given location over an extended period of time. The data they produce can be accessed remotely, thus negating the need for a human to enter the space and potentially expose themselves to a dangerous concentration. Meanwhile, portable sensors are more suited to confined spaces or locations which will receive less footfall. Capable of detecting unsafe concentrations of gas in their vicinity, they can be carried or worn by personnel as they go about their daily routine and sound an alarm when triggered, thus guaranteeing the safety of the individual in question and identifying pockets of troublesome gas at the same time.

Within these two broad categories, there are a number of specific techniques which sensors use to detect gases. These include (but are not limited to) combustible gas sensors, electrochemical gas sensors, infrared imaging sensors, infrared point sensors, photoionization sensors, semiconductor sensors and ultrasonic sensors. New technologies are being developed all the time and as such, this list is not an exhaustive nor an evergreen one.

What things should you keep in mind when installing a gas detector?

With such an extensive range of gas detectors available, it’s critical that site owners carefully consider all of the criteria surrounding their decision before installing a gas detector. This will include the types of gases being detected, the purposes of the data collection and the particular work being carried out in their vicinity.

As well as choosing the type of gas detector wisely, it’s also incumbent on a site owner to make sure that the sensors are positioned correctly. Some gases are heavier than ambient air and thus have a tendency to sink to the bottom of an enclosed space, while others are lighter and will rise to the top of a room. Depending on the gas in question, the detector should be located accordingly. Also, when reading or servicing a gas detector, the individual in question should not raise their head above it so as to ensure that they are not exposed to a pocket of gas that could prove damaging or deadly.

The final point to consider is that gas detection is not merely a set-and-forget discipline. Sensors require regular maintenance and upkeep to ensure that they are in good working order. As such, a site owner must make sure that a servicing schedule is in place to identify any faults with the gas detection system as early as possible and minimise the risk, potential damage and financial costs associated with them.

For those interested in a more in-depth exploration of the topic, the The CoGDEM Guide to Gas Detection is now available online and discusses all of the above (and much more) in far greater detail.