Why it's important to avoid air compressor moisture

External factors and the compression process itself produce water vapor, which can lead to impurities. You'll want to avoid air compressor moisture for clean dry operations.

External factors, like humidity and ambient room conditions, and the compression process itself introduce water vapour in compressed air, which can lead to microorganisms, mould, and other impurities in equipment. Installing dryers, aftercoolers, and drains is crucial to avoid moisture in your air compressor.

Maintaining dry air is essential for meeting air quality standards and avoiding maintenance issues, including corrosion and rust. With the right equipment, you'll benefit from a long product lifespan, and guarantee the best possible end products.

The air quality standards mentioned relate to your industry's ISO-8573-1 class. These guidelines include pressure dew point (PDP), particle content, and oil per cubic meter. With some oil-injected air compressor equipment, it's inevitable that oil particles end up in the air.

The right drying equipment removes such impurities while achieving an acceptable PDP. This value determines how much water vapour remains in compressed air. The lower the PDP, the drier the air.

Read on below to learn about each step in the drying process, and how to reach clean air quality levels.

Why it's important to avoid air compressor moisture


In related articles, we go further in depth on the two main dryer types, which are refrigerant and desiccant / adsorption ones. If you work with compressed air, you'll need one of these to protect your equipment and reputation.

With a PDP of around 4 °C, a fridge dryer is sufficient for most applications. However, if you work with sensitive industries, you'll need a desiccant dryer for PDP levels of -40 °C or lower.

Below, you'll find an overview of how each works to help avoid air compressor moisture.


Refrigerated (fridge)

It should come as no surprise that fridge dryers cool air to remove moisture. This process occurs with an air-to-heat exchanger and air-to-refrigerant exchanger.

As the temperature drops, air moisture condenses and is drained. After this step, compressed air is reheated to room temperature, lowering the PDP and preventing condensation on the pipes.

Read this article to find out all advantages of a refrigerant dryer.

Desiccant (adsorption)

These dryers use a desiccant or hygroscopic material (similar to Silica Gel) to remove moisture from compressed air. Desiccant dryers typically have two drums filled with an adsorbent material.

The first drum removes water vapour by attracting water vapour to the desiccant. When that drum is saturated, the second one is used. While this is happening, the first drum becomes regenerated.

As implied, these dryers need to be replenished. This occurs in various ways, including purge / heatless, heated purge, blower, and heat of compression (HOC). Our guide on desiccant dryers goes further into these processes.

As mentioned above, this equipment is capable of achieving low PDP levels for extremely dry air. Also, if you're concerned with energy consumption, there are highly efficient models.


Typical equipment on an air compressor, an aftercooler is a heat exchanger that cools hot compressed air. This process makes the water precipitate, which would otherwise condensate within the piping system.

There are water-cooled and air-cooled aftercoolers, which come with an automatically draining water separator. This equipment should be placed close to the compressor.

Water separators collect approximately 80-90% of the condensation water. A common value for the compressed air temperature after passing through an aftercooler is approx. 10˚ C above the coolant temperature.

While aftercoolers are an important step in cooling and drying compressed air, they are not a replacement for dryers. They work in conjunction with such machines.


Properly disposing of condensate with an adequate drainage setup is a crucial step of the entire compressed air production process, especially since oil-injected compressors produce environmentally hazardous condensate.

When researching options, you'll generally come across automatic, timer, and electronic drains. These can be installed at various stages, including at dryers, aftercoolers, or storage tanks.

Regardless of what you choose, you'll want to make sure the environmental guidelines are followed. A proper installation should include an oil-water separator leading to a foul drain.

You can find more information about local regulations at your recycling centre. You don't want to be in violation of any rules concerning waste disposal. Doing this could lead to fines and a loss of reputation.

We're here to help you avoid air compressor moisture

As pointed out in this article, avoiding air compressor moisture is a crucial step in the production process. If you're uncertain as to what makes the most sense for your industry, feel free to get in touch with our team.

We're here to help point you in the right direction. The last thing you want to worry about is high water vapor levels.