What Is Dew Point and Why Does It Matter in Compressed Air?

Dew point is one of those terms that gets thrown around a lot in compressed air conversations but it’s rarely understood properly.

If your site relies on dry air for product quality, instrumentation, packaging, or preventing corrosion, dew point should matter to you. Here’s why...

Dew Point Explained

In simple terms, dew point is the temperature at which water vapour in the air will start to condense into liquid.

The lower the dew point, the drier the air.

So, when someone says their system has a “dew point of -40°C,” it means the air is so dry that moisture won’t start condensing until it’s cooled to -40°C. That’s typical for desiccant dryers in critical applications.

A “+3°C dew point” (which you’ll get from most refrigerated dryers) means moisture starts condensing as soon as the air cools below 3°C - which is fine for general plant air, but not always suitable for sensitive processes.

Why It Actually Matters

Most sites don’t monitor dew point directly. They assume the dryer is working and move on.

But here’s the problem:

A failing dryer won’t always trigger alarms

If the dew point creeps up to +10°C or higher, it might not trip out your dryer, but you’re still blowing wet air into the system.

Moisture builds up downstream

This causes corrosion in pipework, poor-quality end product, and damages pneumatic equipment.

You lose energy

Higher moisture levels mean pressure drops, more condensate removal, and less effective tools.

We See This All the Time

In our compressed air audits, we often install temperature and dew point loggers to confirm dryer performance. It’s not unusual to see:

Fridge dryers delivering +10 to +15°C dew point (instead of +3°C)

Desiccant dryers passing full flow through only one tower

Dryer bypasses left open, feeding raw air into production lines

And nobody knows because there’s no dew point sensor, or it’s never been checked.

What Should Your Dew Point Be?

Application Typical Required Dew Point:

General plant air (tools, blowguns) +3°C

Packaging / electronics -20°C to -40°C

Food, pharma, instrumentation -40°C or lower

If you're unsure what your process requires - or whether you're actually achieving it - it's worth checking.

How We Can Help

At Compressed Air Energy Solutions, we offer two routes to confirm dew point performance:

As part of a full system audit:

We install dew point loggers alongside flow and pressure monitoring to gather accurate, week-long data on your system.

Through compressed air quality testing (ISO 8573):

This includes dew point measurement along with oil carryover and solid particulate analysis, ideal for sensitive or regulated environments.

Whether you want to spot performance drift or confirm your air meets ISO standards, we’ve got it covered.