There are many reasons why moisture in air compressors can be problematic. Ranging from damaging equipment to causing blockages in air lines, moisture in air compressors can cause costly issues that will add time and money to your projects. 
We have compiled a guide of top tips to ensure your air compressors are protected and can perform to the best of their ability. In this guide, we will cover: 

  • What are Compressed Air and Air Compressors?
  • The Damage Moisture Causes in Air Compressors 
  • What Causes Moisture in Compressed Air
  • Ways to Remove Moisture From Compressed Air 
  • Ways to Prevent Moisture in Compressed Air 
  • What You Can Do To Protect Your Air Compressor 

What Are Compressed Air and Air Compressors?

Compressed air has many applications. From construction to food processing, compressed air can be crucial in many different industries. This means it is critical for compressed air to be free from contaminants as it can be used to power tools and when handling food products.

Air compressors are used to form compressed air. They do this by drawing in air from an inlet valve, compressing the air, going through various channels, and then being released through a discharge valve. This means the air within an air compressor has many processes to undergo before use. 

Along this journey, contaminants, including moisture within the air, may end up in the final compressed air, but what does this mean for you?

The Damage Moisture Causes in Air Compressors 

Moisture can cause both damage to equipment and contamination, especially when used in the food industry. The damage moisture can cause to machinery and equipment can be costly, so it is imperative your air compressors are kept up to standard to ensure minimal additional cost. 

Corrosion of Components

Elements of machinery may be affected by excess moisture in compressed air. The moisture can cause rust to form, causing damage to equipment. This can affect the pipes of machines or the machine itself. 

Reduced Lifespan of Equipment 

The damage from moisture can cause equipment to have a reduced lifespan. This can be costly as machines and tools will have to be constantly replaced if the issue is not resolved. 

Clogged Airways 

The addition of moisture can also cause a build-up within the pipes of the machinery. Rust and ice can build up to form blockages that will also ultimately damage equipment as a whole. 


In some industries (e.g. the food industry), it can be essential to avoid contamination. If there is moisture and other contaminants, such as oil particles, in the compressed air, this can lead to quality standards and guidelines not being met, leading to further issues. 
This means processes must be implemented to ensure the most pure form of compressed air can be used at the end of compression, so what causes moisture in compressed air?

What Causes Moisture in Compressed Air

Moisture is eliminated from compressed air during the cooling and moisture separation process within the air compressor. Once normal air is compressed, it cannot hold as much water. This means as compressed air is cooled, water vapour condenses into water and needs to be removed. 

If not removed, the moisture can damage equipment, decrease the efficiency of tools, and cause quality issues when tools are used. So how can moisture be removed from compressed air?

Ways to Remove Moisture From Compressed Air 

If you are already aware of moisture in your air compressor, here are a few ways to remove this excess liquid:

Draining the Water

This may seem simple, but draining the excess liquid from your air compressor is the number one way to remove any moisture from your air compressor. As it is such a simple task, many people can forget about it. By using drain valves, you can easily drain excess liquid from different areas where moisture usually accumulates, such as in air dryers and low areas of your piping. 

Air Dryers 

The primary purpose of air dryers is to remove moisture and contaminants from compressed air. There are a few different types of air dryers that have different methods for removing moisture from compressed air. 

Refrigerated Air Dryers

By using a lower temperature, refrigerated air dryers remove additional moisture by separating the moisture from the air. The liquid is then removed using a drain valve. 

Desiccant Air Dryers

Using the process of adsorption, a material such as silica gel is used to attract water, removing it from compressed air. This form of air dryer is most commonly used for situations where very dry air is needed, such as in the pharmaceutical industry. 

Membrane Air Dryers 

A semi-permeable membrane is implemented to remove excess moisture from compressed air. Water vapour is able to pass through this membrane whereas compressed air is not, leading to the separation of moisture from the final product. 

Deliquescent Air Dryers

Using a hygroscopic substance, moisture is absorbed from the air, forming a salt solution. A hygroscopic substance is a material that absorbs moisture from the air. This solution is then removed from the machine. 

Other Methods of Removing Moisture

Some other methods to remove excess moisture include:

  • Air Receiver Tanks: This component of an air compressor acts as a storage tank that cools the compressed air again, removing any additional moisture. 
  • After-cooler: After-coolers also remove moisture through condensation by changing temperatures to ambient air temperatures. 
  • Absorption drying: Using a chemical process, water vapour is removed using some form of absorption material such as sodium chloride.

Ways to Prevent Moisture in Compressed Air 

Although removing moisture from your air compressor is beneficial, prevention is the key to ensuring your equipment is protected from moisture damage. Here, we have listed some ways to prevent moisture in your air compressor:

Regular Air Compressor Maintenance 

One of the most essential tips to take away from this guide is to keep regular preventative maintenance of your air compressor. This can include:

  • Regularly draining water from the air compressor 
  • Ensuring all elements of the air compressor are working effectively
  • Maintaining the oil/water separator
  • Performing general maintenance

By keeping track of maintenance works for your air compressor, tasks such as draining the water from the system will be regularly monitored minimising the risk of excess liquid build-up. 

Air Compressor Moisture Indicator 

Indicators allow you to see if there is any excess moisture in the air compressor system before it becomes a bigger issue. There are two types of moisture indicators that may be useful:

Moisture Indicator 

A moisture indicator is an external device that can be added to any part of your air-compressing system after your air dryer. This device will show a colour change from blue to pink when moisture increases in the system. By checking this indicator regularly, you will be able to diminish the effects of moisture damage. 

Dew Point Sensor 

A dew point sensor is used to determine the pressure dew point. This is the point at which condensation begins based on temperature. Air dryers typically have these built into them. It is, therefore, ideal to check these sensors routinely to ensure moisture is kept to a minimum. 

Decrease the Humidity of the Air

One way to prevent a build-up of moisture in an air compressor is to decrease the humidity of the air entering the air compressor. This will reduce the water content in the air that is entering the air compressor, meaning less water has to be removed once the air is compressed. 

Ensure An Optimum Room Environment 

If your air compressor is placed in a well-ventilated area that is well insulated, less moisture should be in the air going into the air compressor. Other tips to ensure an optimum room environment include:

  • Keeping the room cool 
  • Adding a dehumidifier if needed 
  • Minimising any leaks in the room 

If your air compressor is placed outside, there may be fewer options for reducing the moisture in the air. 

What You Can Do To Protect Your Air Compressor 

In this guide, we have summarised the best ways to remove and prevent moisture in air compressors. It is suggested you keep regular maintenance of your air compressor to prevent excess moisture from building up. If you find there is already excess liquid in your air compressor, it is recommended that you start by draining any water from your system. 
If you have any additional questions regarding moisture in your air compressor or want to purchase an air compressor, do not hesitate to contact us, and one of our team will be happy to help. 

Removing Moisture From Compressed Air FAQs 

Can compressed air be too dry? 

It is possible to over-dry compressed air. In most cases, simply removing some moisture may be adequate for the job the compressed air is used for. It is about finding balance in the amount of dryness in your compressed air to not waste time and money. 

How long does compressed air take to dry?

Typically it takes about 5-10 minutes for compressed air to dry. This depends on numerous factors, such as humidity and the temperature of the area. 

What is the difference between an air compressor and an air dryer?

An air compressor is used to compress air simply by drawing in air through an inlet, compressing the air and then discharging the air. On the other hand, an air dryer is used specifically to remove moisture and any contaminants from compressed air. These two machines are implemented hand in hand but are not the same system. 

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