How to audit compressed air system
A simple leak in your compressed air system can waste 20-30% of your air compressor’s output. Auditing your compressed air system can provide a blueprint for how to operate more efficiently. Today, BISON discusses how to audit your compressed air system from the perspective of a professional air compressor manufacturer & supplier, combined with our own air compressor industry experience.
Importance of compressed air system audit
A compressed air system audit is your way of determining how much production you’ve lost. It’s designed to help you identify inefficiencies so they can be fixed and save your organization money in long-term operational costs. Even a single 1/4-inch leak in a compressed air line can cost a facility between $2,500 and $8,000 annually depending on pressure and energy costs, which shows why leak detection matters so much.
Implementing audit recommendations can pay for itself over an extended period, delivering benefits in cost savings, equipment longevity, and system reliability. Some common recommendations from an audit may include:
- Plug undetected leaks.
- Reduce excess pressure.
- Right-size air requirements.
- Replace damaged piping.
- Remove outdated restrictions.
- Add storage capacity.
- Eliminate improper use.
- Monitor system controls.
- Improve heat recovery.
When you can comply with these and other recommendations from the audit, your business may be eligible for several potential energy rebates, saving you even more money on utility costs.
How to audit a compressed air system
Knowing how to audit a compressed air system accurately starts with a professional evaluation—a diagnostic technician will use data logging tools for measuring your load profile (the difference between the CFM and PSI you’re using and what you need to do the job).
From this data, you’ll see graphs showing where you’re wasting energy (and money). This data is critical to identifying any anomalies or air losses causing your air system to overwork and overcompensate. An uncalibrated flow meter can accumulate 5–10% error over time, so establishing a KPI baseline over five consecutive business days of full-load operation before making any improvements helps ensure the readings are trustworthy.
An audit will cover many metrics and factors, and a walkthrough assessment can be done in less than 8 hours or a few days, based on your system’s size and complexity. The things below are recommended to be checked for a complete analysis of your compressor system.
| Step | What to Check | Key Metric |
|---|---|---|
| 1 | Eliminate leaks & pressure drops | Leak rate (<10% target) |
| 2 | Check air filters | ΔP across filter |
| 3 | Eliminate artificial demand | Operating PSI vs. actual need |
| 4 | Review pressure regulators | POU pressure matching |
| 5 | Audit dryer & heat recovery | Dew point / heat recovered |
| 6 | Check storage capacity | Tank size vs. peak demand |
| 7 | Shut off when idle | Off-hours runtime |
| 8 | Establish baseline & monitor | kW per 100 cfm |
Eliminate leaks and pressure drops
The clearest sign is the compressor continuing to load and cycle when no air-using equipment is running. These are the ones responsible for the majority of energy waste, so identify and repair any leaks in your air system piping — a good practice is to install flow meters at the main pipe after the buffer tank and at each branch line feeding different areas, so you can build a baseline of normal consumption and quickly spot when usage drifts upward. Even a 1/8-inch diameter hole in a 100 PSI system can add up to $1,200 in wasted energy over a year, and the true cost scales with orifice size — the larger the hole, the steeper the waste, so it pays to check a range of hole sizes rather than assuming only big leaks matter. That same 1/8-inch hole can waste nearly 20 CFM of compressed air, and every 2 psi increase in discharge pressure raises energy consumption by roughly 1%, so chasing unnecessary pressure is its own drain on efficiency.
- Aging pipes — throughout airline lines, especially worn joints.
- Coupling – check the seals; they may be damaged by installation/use.
- Drain valves – check receivers, filters, and all other equipment with valves.
- Fittings — fittings may have loosened over time.
- Flange connector – where the gasket will need to be replaced.
- Flexible hoses – can cut or tear due to friction.
- Manifold – check closely spaced connections.
- The pneumatic tool ends — Check for leaks in connectors and seals.
Beyond a one-time fix, establish an ongoing preventative maintenance leak prevention program: schedule regular ultrasonic or soap-test inspections, train staff to spot and report hissing sounds or pressure drops, and prioritize repairs by leak size and cost to keep the system consistently tight. A practical benchmark is to keep total system leakage at no more than 5-10% of overall compressed air flow — treat anything above that range as a signal that your prevention program needs tightening.
To quantify leakage, run a quick load/no-load timing test: with all end uses shut off, measure how often and how long the compressor cycles to maintain pressure, then calculate leak rate from the load time percentage; alternatively, isolate the system, note the pressure drop over a set period, and use that decay rate to estimate total leakage. Using the compressor’s load time (T1) and offload time (T2), a total leak rate above 10%, calculated as [(T1x100)]/(T1+T2), is a clear sign your system needs attention.
Check the air filters
Clogged filters restrict airflow, forcing the compressor to work harder and increasing energy consumption. Over time, they also allow harmful contaminants to bypass the filter media and circulate through the system, potentially causing costly damage to downstream equipment. Regularly clean or replace filters to prevent these problems.
In order to optimize savings at the air end, we provide high-efficiency line filters. Clean or change all your filters regularly, and ensure you use the correct filters first.
Eliminate artificial demand
Air compressors manufacturers such as BISON will use higher pressure (PSI) to overcompensate for leaks, pressure reductions, and flow variations to meet flow (CFM) demands. This creates an artificial demand capacity of 25% or more than the requirement. This can eat into your running costs, force your compressor to work harder than necessary, and waste air in the process.
Operating at the lowest possible pressure will significantly minimize energy waste, so rather than manually applying more pressure to meet demand, consider a flow controller or pressure regulator to help improve the efficiency of the air you’re already generating. Variable speed drive compressors adjust their output dynamically to match fluctuating air demand, reducing energy waste compared to fixed-speed units in facilities with variable loads. Reducing system pressure by 14.5 psi (1 bar) can yield approximately 7% energy savings, making it worthwhile to review your pressure settings regularly.
Consider a pressure regulator
A pressure regulator keeps air tools operating efficiently by closely regulating air pressure and minimizing wasted air. Some regulators even have built-in filtration for maximum protection. Consider using them at your air end location.
It’s also worth recognizing that some end uses, such as cleaning, cooling, or agitation, don’t require full line pressure, and comparing point-of-use pressure needs across these tasks can help high-performing units avoid supplying more pressure than necessary.
Estimate air dryer and heating costs
A high-efficiency air dryer removes moisture from compressed air to prevent heat and condensation buildup quickly. Air dryers protect the longevity of your pneumatic tools and machines by cooling and removing moisture that would otherwise contaminate the air and damage your compressor tank, lines, and other components over time. Use the wrong type of air dryer, and you’ll waste money by overworking it for a purpose it wasn’t designed for. As part of your audit, check the refrigerant dryer’s dew point, test the condensate drain for proper operation, and monitor the coalescing filter’s differential pressure to confirm the drying system is running efficiently rather than straining unnecessarily.
Refrigerated air dryers will work perfectly with scroll compressors or piston or rotary screw compressors designed with a built-in aftercooler.
Otherwise, a refrigerated air dryer will work longer and twice as hard to cool the high-temperature air—resulting in wasted energy, shorter dryer life, and money on the bottom line. High-temperature air dryers are designed for this purpose and run efficiently on these heavy workloads.
Most of the compressor’s electrical energy is converted to heat energy, often wasted. Intelligent applications in your system (such as a heat recovery unit) can allow you to use this energy to offset compressor costs. Some higher-performing systems also pair variable speed drive compressors with desiccant drying as additional ways to manage energy use and moisture control, though the actual savings will depend on your specific setup. Take space heating, for example. For large commercial buildings, it is possible to use the heat produced by using your compressor to warm the structure or even just the water for different hot water uses.
Upgrade your storage capacity
Upgrading storage capacity typically means adding an auxiliary tank that fills initially and is drawn on as needed. The more storage you have, the less your compressor needs to run, allowing you to do more with fewer kilowatt hours. However, the longer compressed air stays compressed, the more moisture it builds up. More storage capacity can be a cost-effective solution over time as long as you use the extra air throughout the workday.
Turn off the compressor
It seems simple enough, but many manufacturers leave their compressors on when not in use, such as on weekends or during off hours. This is just needless and a waste of money on energy. Switch off your compressor outside of working hours and when not in use. Install an automatic shutoff timer or simply make shutdown part of the end-of-day checklist.
Conclusion
Compressed air system audits are invaluable tools for industries that rely on compressed air. Whether it’s an energy audit to improve efficiency, a leak audit to reduce energy waste, or a system assessment for overall improvement, these audits help reduce operational costs, improve reliability, and support environmental sustainability — playing an essential role in extending equipment life and lowering total cost of ownership.. Viewed this way, the compressed air system itself becomes a strategic asset—one where combining audit findings with opportunities like heat recovery can strengthen the overall return on the investment you’ve made in your equipment.
By understanding the objectives and processes of different types of audits, businesses can take proactive steps to ensure their compressed air systems operate at peak efficiency while reducing their energy footprint. A practical way to track this over time is to monitor a kW per 100 cfm performance indicator, using a baseline measurement period of roughly 10 days to establish a reliable picture of how the system is truly performing before and after any improvements are made.
frequently asked questions about How to audit compressed air system
Is compressed air audit compulsory?
Although not legally required in some countries, it is essential to have regular compressed air audits to guarantee that your equipment is both safe to use and in good functioning order.
Some countries that require a compressed air audit include the United States, Australia and New Zealand, European countries, and the United Kingdom.
What is the best tool for detecting leaks in a compressed air system?
An ultrasonic acoustic detector detects the high-frequency noises associated with leaks and is an effective tool for finding compressed air leaks. Although other gas monitors can be utilized as well, for early detection and prevention, it is also beneficial to use a checklist to help identify potential leak points, damages, and problems.
For a more thorough audit, a sound approach follows a simple sequence: start with data loggers to capture your load profile, move to ultrasonic detectors to pinpoint suspect areas, then run a pressure drop analysis to confirm the severity of what's found, followed by a visual inspection of fittings and joints, and finally a documented repair-and-retest step to verify the fix held. Working through these steps in order keeps the audit consistent and makes it easier to compare results over time.
It's also worth noting that some models of flow meters can measure air movement in both directions, which helps distinguish a genuine leak from backflow within the piping — a distinction that a simple pressure test alone won't always reveal. Using this kind of bi-directional monitoring alongside your ultrasonic detector gives a clearer picture before you commit to repairs, since a change in flow reading isn't always caused by a leak; sometimes it's air moving backward through a valve or fitting that looks like loss but isn't. Cross-checking readings this way helps avoid chasing a false leak and keeps the repair-and-retest step of your audit focused on the areas that actually need attention.
Does the audit process change for multi-compressor systems or ring mains?
Audit principles stay the same, but data logging should capture each compressor's individual load profile plus overall header pressure, since automatic sequencing controls can mask one inefficient unit. On a ring main, measure pressure at multiple points around the loop rather than only near the compressor room, since localized drops from leaks or undersized branch lines can otherwise go unnoticed.
What instruments are used in a compressed air audit?
A thorough audit uses a data logger to capture load profile, a kW/power meter on the compressor motor, a flow meter or pitot tube for CFM output, pressure transducers at multiple system points, a dew point meter to check dryer performance, and an ultrasonic acoustic detector for leaks. These power, flow, pressure, temperature, and dew point sensors are typically deployed not just at the compressor but across dryers and filters too, so no stage of the system is left unmeasured. Together these instruments quantify exactly where energy and compressed air are being lost.
How long does a compressed air audit take, and what does it cover?
Scope and duration scale with the depth of the review. A quick walkthrough assessment can be done in less than 8 hours or stretch to a few days depending on your system's size and complexity, generally falling somewhere between half a day and two days once you account for facility layout and the number of compressors involved. A full audit, by contrast, typically spans three to ten days and covers energy data logging, true demand measurement, leak detection, air quality particulate testing, and maintenance review, all with little disruption to normal operations. Whichever tier you choose, the audit will cover many metrics and factors, and the output should function as a practical, actionable tool you can walk the floor with—not just a report that sits in a drawer.
