Units of Compressed Air: A Guide

The Hosemaster

June 12, 2024

When dealing with compressed air, it’s incredibly important to understand what unit of measurement you should be using. This will vary depending on the different usages, applications, or industries.

Sometimes, even where you are in the world will influence compressed air pressure measurement units! But don’t worry, here at The Hosemaster, we’re ready to provide you with some clarity – you’ll know your psi from your Pascal in no time.

We’ll also get you up to speed on some must-have air pressure measuring tools, including pressure gauges, air blowguns, and air filters.

First, though, let’s catch up on a bit of compressed air-based general knowledge…

What is compressed air?

Air is a combination of molecules: nitrogen, oxygen, carbon dioxide, hydrogen, and neon—as well as some other rogue particles like pollen and dust.

Compressed air then, is air that has been forced into a small space such as a canister or a tank, depending on the industry or project and how it is being stored, transported, or used, etc.

To compress air, an energy source is required, like a motor or mains supply. Investing in high-quality air compression equipment will help make sure you’re going through the motions as energy-efficiently as possible. In the compression process, the molecules that make up the air are squashed together tightly, which makes them move more (this type of movement is called kinetic energy) and produce more heat.

What is compressed air used for?

Compressed air is incredibly versatile and effective in the transfer of energy and powering of different tools and machinery. That’s why it’s such a common thing to find in so many different types of industries and projects.

Common uses of compressed air include:

Pneumatic tools like drills, spray guns, and sanders.
Air-related processes like air agitation, air blowing, air separation, and air cooling.
Packaging in industries such as food, textiles, pharmaceuticals, and chemicals.
Heating, ventilation, and air conditioning (HVAC) systems.
Refrigeration systems.
Cleaning and drying processes.
Medical tools such as dental tools, nebulisers, and surgical equipment.
Pneumatic breaks in transportation systems (e.g. trains).
Wastewater treatment.

How compressed air is used can be broken down into two overarching categories:

Active air – wherever compressed air actively comes into contact with the subject of the process, e.g. when using an air blowgun to clean something with high-velocity air.
Energy air – wherever compressed air is used to power mechanical work.

How is compressed air measured?

As we mentioned earlier, how air pressure is measured varies depending on the different usage, industry, and even geographical location. However, there are two key categories that air pressure measurement units can be divided into:

Pressure (how strong)
Volume (how much)

Let’s take a look at each of these in more detail…

Pressure

Depending on where you are, you may be more or less familiar with these different air pressure measurements.

Pounds per square inch (psi)

When air is compressed, it naturally wants to try and decompress again. This resistance produces force – and this force can be measured in pounds per square inch (psi). The psi unit of measurement means you can see how much force is being applied to a specific area of space. This then translates into how much force an air compressor is able to deliver.

An image of a 1/8

Buy now – Pressure Gauge - 1/8" BSPT x 50mm Dial

Bar

This unit of measurement is arguably the most internationally recognised and is a standard measure of pressure. Like psi, it measures the pressure (i.e. force) of compressed air as opposed to volume – how strong rather than how much.

Bar is short for ‘barometric’ units and it’s important to note that 1 bar is equivalent to 100,000 pascals (this will make more sense in just a moment).

Kilopascal (kPa) and megapascal (MPa)

The Pascal (Pa) is part of the International System of Units, which means it’s a measurement unit recognised in most countries. Pa is used to measure a whole host of different types of pressure and is considered an official standard for doing so.

In terms of compressed air, Pa is too small of a measurement to make sense, so this is where kilopascals (kPa) and megapascals (MPa) come into play.

1 kPa = 1,000 Pa
1 MPa = 1,000,000 Pa or 1,000 kPa

It’s also important to note that:

1 bar = 100 kPa
1 psi = 6.8 kPa

Top tip: keep a note of these equivalents as the conversions might come in handy!

Volume

On the other hand, you can measure compressed air another way, using volume to calculate how much you have. There are several units of measurement you can use to do this, which we’ll explain further below.

Cubic metres per hour (㎥/h)

This is a metric unit that measures the volume flow of air, i.e. how much compressed air there is, rather than how strong it is or the force it produces. It does this by measuring the volume of air per a set unit of time – in this case, how many cubic metres flow per hour.

Note: this particular unit of measurement is typically used for larger industrial purposes.

Litres per minute (L/min)

Litres per minute is another metric unit, like cubic metres per hour, designed to measure the volume of air flowing for a specific amount of time. This time, the volume is measured in litres (a more standard metric).

Note: 1 CFM is equivalent to a flow rate of 28.3 litres per minute, for example – which leads us nicely onto the next point…

Air compressor capacity (AKA air flow)

Where units of compressed air are concerned, it’s important to consider the capacity of your air compressor. A smaller air compressor is (obviously) able to move less air than a larger one, so the size you’ll need really depends on the project you’re working on.

The capacity of an air compressor describes how much compressed air it can supply per unit of time. This is known as ‘air flow’ and is typically measured in:

Litres per minute (l/min)
Litres per second (l/sec)
Cubic metres per minute (m³/min)

You might also see the imperial measurement version being used: cubic feet per minute (CFM), so it’s also important to note that 1 CFM is equivalent to 28.3 l/min (as we mentioned above).

Popular air pressure tools

As compressed air is so diverse and used widely across different industries and applications, there are also many different associated tools and accessories. Below, we put the spotlight on three popular air pressure tools that you might need.

Pressure gauge

An air pressure gauge is one of the best and easiest tools you can use to measure compressed air. They work by measuring the pressure of a gas or liquid relative to the atmosphere and are suitable for use across a range of different applications and industries.

Here at The Hosemaster, we stock many different types of pressure gauges, including HVAC pressure gauges, panel mounting pressure gauges, and glycerine-filled pressure gauges.

100mm Glycerine Filled Gauge

Buy now – 100mm Glycerine Filled Gauge

There is also a variety of different mounting and threaded connection options for you to choose from, so there’s sure to be something to meet your needs.

Air blowgun

Air blowguns are used to shoot compressed air at a high speed. Generally, they’re used for things like cleaning, drying, and removing debris, which makes them common in industries such as agriculture, automotive, packaging, and lab research.

Air filters and regulators

We always recommend incorporating air filters and regulators into your compressed air system. This will help improve the quality of the compressed air, allow easier adjustment of the airflow for the user, and reduce friction on components when in use.

Measure air pressure accurately with The Hosemaster

Now you do indeed know your PSI from your kPa – and everything else in between – it’s time to make sure you’re kitted out with the best quality compressed air measurement tools. Investing in top-quality products will ensure that the readings are accurate and in some cases, will also help reduce energy inefficiencies and loss of energy.

Here at The Hosemaster, we stock a wide range of pressure gauges designed to suit a whole host of different applications and industries.

Hopefully you’re able to find everything you need on the website but if you’ve got any questions, please don’t hesitate to get in touch for some further guidance – our 5-star-rated customer service will have you covered.