Air Hose Essentials: Fittings, Pressure, and Materials

Air hoses are lengths of hose made of industrial grade materials like rubber or PVC to provide flexibility and easy manoeuvring while remaining durable to high-pressure conditions. They are used to transfer pressurised air or other types of gas from an air compressor to another location, typically to tools that use this pressurised gas as a form of power. 

Air hoses are not like everyday hoses, as they must be able to deliver a consistent level of pressure while being strong enough to withstand this pressure without tearing or breaking. They are typically accompanied by airtight connectors and end fittings made of brass or steel that link them to air compressors or pneumatic tools. 

Air hoses are essential in the world of pneumatics, which is why it’s also often called pneumatic tubing. Wherever you find pneumatics you’ll find air hoses, making them prevalent in a range of industries like manufacturing and engineering.

Air hoses come in a range of types, each tailored to specific use cases and requirements. We’ll go into four of the most common types of air hoses below to help you choose the best air hose for your work. 

Standard Air Hose: A standard air hose in New Zealand is a straight tube with no twists or coils. These are typically the best choice for laying out on flat surfaces and can be easily stored with a retractable air hose reel or just simply looped up like any other cable or hose.  Retractable air hose reels are typically a better solution for storing standard hoses as they typically have a crank handle which can be attached to walls or ceilings. Standard air hoses are usually used for hand operated tools like paint guns as they do not resist when pulled giving more freedom to the user to move around and operate machinery. 

High Pressure Air Hoses: For applications that require a substantial amount of air pressure, high-pressure air hoses made with reinforced rubber are often required. These hoses are more durable as compared to traditional air hoses to handle increased stress and pressure levels, making them suitable for tasks that require a strong and consistent air flow. High pressure air hoses are typically used alongside air impact wrenches, hydraulic equipment, or other types of machinery that rely on high pressure air. You’ll usually need this type of air hose if you are working with air pressure levels of 20 bar or up. 

Retractable Air Hoses: Retractable air hoses or coiled air hoses are characterised by the tensile coils present along the length of the hose. These make them similar in appearance to traditional telephone wires. The coils are highly resistant, making it so that the hose will revert back into its original shape and length once the hose has been released by the user. This allows them to be stored more easily and helps prevent tripping hazards in environments where safety is a priority such as on a factory floor. 

Heat Resistant Hose: Heat resistant air hoses are engineered to withstand elevated temperatures, making them ideal for applications where heat is a concern, such as near hot machinery or in welding operations. High temperature ratings for air hoses can range from 40℃ all the way up to 260℃ making them ideal for industrial applications. 

The amount of pressure required for a task determines what kind of air hose will suit the task. Air hoses are specifically designed to operate at different pressure levels, so make sure the hose you select for your project is compatible with the amount of pressure required. 

Gas pressure is normally measured in two different units, bars or pascals. Pascals are a smaller unit used to measure the stress and resistance of gas within a confined space, and replaced the older metric, pounds per square inch. Bars on the other hand are approximately equivalent to air pressure at sea level. 

When selecting your air hose you need to be aware of the maximum pressure tolerance needed for the task. It makes sense to choose a hose with a higher tolerance to avoid any potential equipment failure.

Connectors and fittings are crucial pieces of equipment used with pressurised air and gas tools, ensuring consistent flows of pressure. Air hose fittings are used to connect compressors with tools, or to attach lengths of a hose together or divide a hose into different directions. As with other types of connectors and cables, air hose connectors typically have male and female versions that must be used as a pair. 

The most common types of air hose connectors include, ¼” British Standard Pipe Thread (BSPT), ¼” Push Connector Locking (PCL), and ⅜” National Pipe Thread (NPT). 

Despite us being in New Zealand, British Standard Pipe is still used here and around the world. It is a standard for connecting threaded tapered male to female pipes and tubing. Male fittings are labelled as “BSPM” while female are labelled “BSPF”. 

PCL Couplings are another common type of connector made by the British company Pneumatic Components Ltd. They are ideal for use in quieter settings due to their design which includes a collar which exerts backward pressure on the hose. 

NPT is a standard similar to BSPT but with a steeper angle. NPT and BSPT connectors are compatible but will not create a seal when joined together. Male NPT connectors function by stretching the female receptacle and creating a tight seal. 

Most fittings for air hoses are made of aluminium, brass or steel. Ensure that each of the connectors you use have been quality tested as sturdiness and reliability are important. 

There are also another class of air hose fittings called quick release couplings which make use of O-rings instead of valves. They are less prone to twisting and are more convenient to take on and off as compared to other connectors. 

Coiled or retractable air hoses typically have built in male and female connectors for connection to compressors, tools, or gas tanks. 

Additional accessories include: 

• Tube cutters for ensuring the air hose is the correct length
• Crank Operated air hose reels for air hose storage
• Pressure washers to help create a tighter seal between fittings and air hoses
• Tube clips for securing air hoses to surfaces
• Hose tails which are used to connect couplings to air hoses
• Regulators and filters to control the pressure and quality of air delivered through the air hose

As with materials, the size of the air hose you need depends on the amount of pressure needed. The main considerations to think of when selecting the size of your air hose are pressure drops and manoeuvrability. 

Pressure in an air hose drops as the gas travels from the compressor to the end point of the hose, so the longer the hose the greater the pressure drop. Fittings can also result in further pressure drops as they typically impact the internal diameter of the hose. Bends or kinks in the hose can also cause pressure to drop due to their effect on the internal diameter of the hose. 

Pressure drops will require the air compressor to run at a higher setting and consume more energy, making it less cost efficient. Generally you should aim for a pressure drop of no more than 3% of the total or 0.1 bar. To calculate pressure drops you will need to look into the internal diameter and length of the hose, the rate of airflow, and the number of couplings/bends in the hose. 

Maneuverability is the other thing to consider when deciding what size air hose to use. For example, someone using a paint gun likely needs to move around, as compared to someone using a hydraulic wrench who typically remains stationary. 

Air hoses typically come in almost any length imaginable but the most common are 30, 50, or 100 metres. The lengths can be further adjusted by cutting or coupling the hose, but this can lead to pressure drops as mentioned previously. 

Air hoses also come with differing internal diameters ranging from as small as 1.2 millimetres up to 25 millimetres. 6mm, 8mm, and 10mm are the most common, and there are even percentage variations of 6mm internal diameters available like 6.2, 6.3 and 6.5. 6mm is typically enough for most handheld tools but for any larger industrial applications a higher internal diameter will be required. The internal diameter of the hose directly correlates with the flexibility and weight of the hose, so keep this in mind if you value manoeuvrability over pressure capacity. 

While they may appear straightforward, air hoses play a significant role in powering pneumatic equipment from impact wrenches to paint sprayers. Though unassuming, the variety and types of air hoses can be baffling for those just starting out with pneumatics. 

The right air hose can make your projects more efficient, your workspace safer, and your tools more reliable. Whether you’re a professional tradesperson, a DIY enthusiast, or simply someone looking to better maintain your equipment, we hope you found this guide helpful.