An Introduction to Contaminants in Compressed Gas and Natural Gas 

What are contaminants and how can effective moisture measurement keep them under control? 

Contamination can have subtly different meanings in science, depending on the environment and the application. A wide range of substances are known as contaminants, such as pollutants, toxins, and impurities. However, in most instances, a contaminant is any substance that exists in an environment where it is not intended to be, and that is certainly the case when considering contaminants in a location such as a gas stream. Think of contaminants more in terms of diluting a pure gas with other elements, rather than the negative environmental connotation that the words ‘pollution’ and ‘toxins’ usually have. That is not to imply that there isn’t an environmental impact of many of the contaminants we discuss here, but that is not the focus of this article. 

We will look at contaminants as they pertain to two examples: compressed gas and natural gas. 

The primary contaminants in compressed gas and natural gas streams are as shown below: 

How does the gas stream become contaminated?

Contaminants are either a constituent part of the gas or are added to the stream through treatment or transfer. In the case of natural gas, contaminants such as carbon dioxide are a normal part of many natural gas streams.  Meanwhile, glycol is used in the drying process and can accidentally enter the stream if proper filtering is not used. 

Why are we concerned about contaminants? 

Often, contaminants have some form of unfavorable effect on the sample or the system. The main concern of natural gas providers is getting quality gas to the consumer, so they want to remove contaminants that will slow down or clog the pipelines and dilute the quality of their products. Similarly, compressed gas treatment focuses on the quality and safety of the final product and it, of course, remains important to protect pipelines and equipment; however, as compressed gases are often used in medical applications, the focus is more on whether they are clean enough for this purpose. 

Let's take a closer look at a specific contaminant – moisture.  

What are the effects of moisture as a contaminant?

Moisture is a particular concern because it can cause various issues on its own and affect other components and pollutants in the system. The presence of water or ice in pipelines can block or stop the flow of gas and can damage the machinery and equipment. Importantly, even a small solid object, like an ice cube striking turbine blades, has the potential to cause them to break apart due to the high speed at which they operate. Water is also a terrible fuel additive as it does not burn well, reducing the fuel's overall effectiveness. Additionally, water influences other contaminants: for example, moisture and dust can cause bacterial growth. Moisture is also a critical factor in oxidation, rust formation and corrosion, leading to the degradation of pipework and machinery. When mixed with hydrocarbons, water forms hydrates, causing solid hydrocarbons within natural gas pipelines. This prompts more frequent maintenance and cleaning procedures, commonly known as "pigging."  

If you are interested in finding out more about the effects of moisture, please check out our other blogs on this subject, including Oxygen and Moisture: A Costly Combination. More related blogs are listed at the end of this article. 

In our follow-up blog article, we will explore the effects of oxygen and hydrogen sulphide as contaminants. 

What is the solution to the contamination problem? 

Natural gas companies work to strict guidelines that dictate the quantity and contamination limits for the caloric content of sales gas. The International Organization for Standardization (ISO) has a range of standards specific to natural gas, like ISO 13686, which lays out the parameters required to define natural gas. There is also an ISO standard for compressed air quality and acceptable contaminant limits, ISO 8573.  

So, how do you combat contaminants?  

1. Knowledge. The first step is measurement and monitoring. For that, you need to know what is in your stream and compare that to what should be there. These stream elements can change over time, so a continuous online measurement – using an instrument such as an Easidew Advanced Online monitor – is a good idea. Or, for multiple streams, you may prefer a portable spot-check measurement device such as the Easidew PDP Dryer Portable. 


2. Filtering is the easiest way to reduce damage to equipment. There are different filters that remove contaminants in various ways, but the most common is the particulate filter. This removes particulates without stopping the flow of gases. Filters can be added to a pipeline as an individual part or at the point of use, like the Easidew Sampler block.  


3. Maintenance. Keeping pipework and machinery clean and working efficiently will reduce the chances of accidentally adding contaminants throughout the system. Replacing rusty pipes will cut down rust particles, and cleaning and replacing the oils on compressors will reduce the amount of oil in the system. 

Contaminants as a force for good

Lastly, let us look at some of the positive uses of contaminants. In the semiconductor industry, contaminants are intentionally introduced to semiconductor chips through a process known as doping, fundamentally altering their electrical, structural, and optical properties. These doped semiconductors are indispensable components of modern electronics. For example, doping silicon with phosphorus or arsenic creates N-type semiconductors by adding extra electrons, thereby enhancing their electrical conductivity. Conversely, adding boron or gallium (elements with fewer valence electrons) results in P-type semiconductors characterized by "holes" that positively impact their performance. 

In metallurgy, the introduction of carbon into iron to create steel exemplifies how contaminants can improve material properties. The presence of carbon, considered an impurity, significantly enhances the strength and fracture resistance of the iron, making steel a vital alloy in construction and manufacturing. An alloy is a mixture of chemical elements, usually including one metallic element. These mixes offer superior properties compared to pure elements. These properties can include increased strength, corrosion resistance, or simply reduced production costs. 

The glass manufacturing industry also benefits from the deliberate addition of specific metal oxides—contaminants that impart desirable qualities. Iron oxide, for instance, produces green or brown-tinted glass, while cobalt oxide is used to create blue glass. These metal oxides not only add aesthetic value but also control light transmission, providing both functional and decorative advantages. 

In conclusion 

The easy way to understand and manage contaminants in various industries, to maintain system efficiency and ensure product quality, is to measure them. From the compressed gas sector to natural gas providers, impurities such as moisture, oil vapors and sulfur compounds can have significant negative impacts. Moreover, the need for strict adherence to standards, such as those set by bodies such as the International Organization for Standardization (ISO), underscores the importance of precise contaminant control. However, it's also essential to recognize that not all impurities are undesirable; the strategic use of contaminants across various industries showcases their potential to drive innovation and enhance material properties.  

For more information like this, please check out our other blogs. For advice on your own contaminant conundrum, please get in touch with our knowledgeable sales and application support teams. Contact us today. 

Related Blogs 

Why do you need Dew-Point Sensors to Measure Moisture in Natural Gas? 

Moisture Measurement in Carbon Sequestration and Utilisation 

Sustainability, Moisture Measurement and Energy Costs 

How to Ensure Compressed Air Safety and Quality in Healthcare

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