COMPRESSED AIR MEASUREMENT

Compressed Air Measurement in 2026 / 2027

Which trends are shaping the future of compressed air measurement technology?

ISO 8573-1 is under revision, ISO 8573-5:2025 is published and EU energy audit deadlines land in October 2026. Seven shifts reshaping how plants specify, install and measure compressed air – with the numbers, standards and deadlines behind each one.

Seven shifts already changing how compressed air is specified, installed and measured

Compressed air measurement is changing faster than at any point in the past decade – and not for the reason most articles give. Sensors getting smarter is the least of it.

What is actually moving is the ground underneath. The standards that define acceptable air quality are being rewritten, the regulations that require you to prove your energy consumption are taking effect, and the cost of not knowing has risen with the price of electricity.

Table of Content

20–30 %

Of compressor output lost to leaks

76 %

Of lifecycle cost is electricity

0.001

mg/m³ oil now measurable

11 Oct 2026

EU energy audit deadline

1. Why Compressed Air Measurement Is Changing Now

The US Department of Energy puts compressed air at roughly 10 % of industrial electricity consumption, and electricity at about 76 % of a system’s ten-year lifecycle cost.

In a plant where that load is barely instrumented, every efficiency decision is an estimate – and every compliance claim rests on a number nobody measured.

Three forces at work:

Standards being rewritten – ISO 8573-1 under revision, ISO 8573-5 reissued in 2025

Regulation taking effect – EU energy audits due 11 October 2026

Electricity prices making the unmeasured load expensive

Instruments that now resolve parameters previously sampled once a year

Data expected to be traceable, not just present

2. What a Modern Monitoring System Measures

Six parameters, one dataset. Flow and power answer what the system costs; dew point, oil and particles answer whether the air is fit for the process.

Flow

Volume or mass flow in m³/h, Nm³/h or scfm. The basis of every consumption, leak and specific-power figure.

Pressure

System and differential pressure in bar(g). Each additional bar of generation pressure carries a measurable energy penalty.

Pressure dew point

In °Ctd, downstream of the dryer. The parameter most likely to fail, and the cheapest to watch continuously.

Oil vapour

Residual oil in mg/m³. ISO 8573-1 oil Class 1 means 0.01 mg/m³ or less – liquid, aerosol and vapour combined.

Particles

Counts per m³ across the 0.1–5.0 µm size bins ISO 8573-1 uses to define particle classes.

Electrical power

kW at the compressor. Combined with flow it gives specific power – the one number that benchmarks a whole station.

3. Permanent Monitoring Is Replacing the Periodic Audit

ISO 11011:2013 defines how a compressed air system assessment is conducted across three subsystems – supply, transmission and demand. What it cannot do is tell you what happened last Tuesday night.

The standard method for establishing a leak baseline is to measure flow during non-production hours. The US Department of Energy states that leaks can waste as much as 20–30 % of a compressor’s output, and recommends a leak-reduction target of 5–10 % of total system flow as typical for industrial facilities.

You cannot see where you sit against that – or watch the figure creep back up over the following year – from a single campaign.

Permanent metering also supplies the before-and-after evidence a savings project needs to be signed off, and then to be shown to have worked. In practice most plants start with a portable logger for the initial assessment, then keep the measurement points with permanently installed data loggers and gateways feeding monitoring software.

What a snapshot cannot show:

Weekend and night-shift leakage baseline

Shift-to-shift variation in demand

Slow dryer degradation over months

Whether last year’s savings held

Artificial demand created by pressure drift

4. The Air Quality Standards Floor Is Moving

ISO 8573-1:2010 moved to ISO stage 90.92 – “to be revised” – on 4 December 2025, and a successor is in development as ISO/AWI 8573-1. ISO 8573-5 was already reissued in July 2025. The reference framework for compressed air purity is being updated for the first time in 15 years.

ISO 8573-1:2010 specifies purity classes for the three contaminant groups that matter in compressed air – solid particles, water and oil – written as a three-part designation in that order. A specification of ISO 8573-1:2010 [1:2:1] means particle Class 1, water Class 2 and oil Class 1.

Two things that are routinely misunderstood

Class 0 does not mean zero contamination. The standard defines it as “as specified by the equipment user or supplier and more stringent than Class 1”. A Class 0 claim without a documented figure is not a specification at all – and it applies to all three contaminant groups, not just oil.

Oil Class 1 is a real, measurable number. A total oil content of 0.01 mg/m³ or less, covering liquid, aerosol and vapour together.

Where the series stands today

Part	Subject	Current edition
ISO 8573-1	Contaminants and purity classes	2010 – under revision
ISO 8573-2	Oil aerosol content	2018
ISO 8573-3	Humidity measurement	1999
ISO 8573-4	Solid particle content	2019
ISO 8573-5	Oil vapour content	2025 (replaces 2001)
ISO 8573-6	Gaseous contaminant content	2003
ISO 8573-7	Viable microbiological contaminant content	2003
ISO 8573-8	Solid particle content by mass concentration	2004
ISO 8573-9	Liquid water content	2004

The ISO 8573 series as of July 2026. Purity classes live in Part 1; every other part is a measurement method.

Purity classes appear in customer contracts, GMP documentation and food-safety schemes, usually cited with an edition year. When Part 1 is republished, those specifications will need review – and so will the instrumentation chosen to verify them.

5. Oil Vapour Moves From Annual Sample to Continuous Readout

Flow and dew point have been monitored continuously for years. Oil vapour has not.

Photoionisation-detector instruments now resolve residual oil down to 0.001 mg/m³ – an order of magnitude below the ISO 8573-1 oil Class 1 limit. The same applies to particles: laser counters covering 0.1–5.0 µm map directly onto the ISO 8573-1 size bins, and stationary purity analysers combine both with dew point in one instrument.

The qualification that matters

Continuous PID monitoring is not a substitute for ISO 8573-5:2025 compliance testing, which requires pressurised sampling and gas chromatography. Likewise, ISO 8573-4:2019 requires partial-flow particle sampling under isokinetic conditions.

The two are complementary. The compliant test establishes the certified figure. The continuous instrument tells you the day something changed – a failed filter element, a compressor running hotter, carryover after maintenance – instead of six months later.

0.001 vs 0.01 mg/m³

Sensor resolution against the ISO 8573-1 oil Class 1 limit

Use each method for what it does:

ISO 8573-5:2025 gas chromatography – the certified figure

Continuous PID monitoring – detects change between tests

ISO 8573-4:2019 isokinetic sampling – certified particle count

Permanent laser counter – the class the air meets today

6. Measurement Uncertainty Becomes a Purchasing Criterion

Buyers are beginning to ask what a reading is worth, not only what the instrument costs. When flow and power measurements are combined into an energy KPI, their uncertainties combine too – and the error band can be wider than the savings the project was meant to deliver.

Specific power – electrical input divided by delivered air, expressed as kW per m³/min or kW per 100 cfm – is the headline benchmark for a compressed air station. It is a derived value. If power carries ±1 % and flow ±5 %, the combined uncertainty is roughly ±5 % in quadrature, and up to ±6 % in the worst case.

What that costs in real money

A 500 kW installation running 7,000 hours a year consumes 3.5 GWh – about €525,000 of electricity at €0.15/kWh. A ±6 % band on the KPI derived from it is ±€31,500 a year of uncertainty, comfortably larger than a typical efficiency project’s first-year saving.

Why turndown matters more than headline accuracy

Headline accuracy is quoted at or near full scale. But the savings in a compressed air system are found at the bottom of the range: night-time flow, weekend baseline, idle consumption. A meter with an excellent full-scale figure and a narrow turndown is not measuring where the money is.

Our own 10 tips for selecting a flow meter works through the trade-offs in more detail.

Technology	Reads	Typical turndown	What decides it
Thermal mass insertion or inline	Mass / standard volume directly	High (order of 100:1)	No separate pressure and temperature compensation; negligible pressure drop; resolves low flows, so leak and idle baselines stay visible. Calibrated per gas; unsuitable for wet or condensing air.
Differential pressure orifice, Venturi, pitot	Volumetric – needs p/T compensation	≈3:1 orifice ≈10:1 cone/wedge	Well established and governed by ISO 5167. The square-root flow relationship caps turndown, and the permanent pressure loss is an ongoing energy cost.
Pitot tube compressor discharge	Volumetric	Medium	Tolerates hot, wet, oil-laden air at the discharge point, where other principles struggle. Not a low-flow instrument.
Vortex	Volumetric	Medium	Robust, no moving parts. Below a minimum Reynolds number the signal becomes unstable and the low-flow cut-off forces the output to zero – so the low flows where leakage shows are typically not registered.
Ultrasonic clamp-on	Volumetric	Wide	Installs without breaking into the line. In compressed air work it is mostly applied to water and other liquids; confirm suitability for gas at the given pressure and pipe size.

Indicative characteristics. Confirm accuracy, turndown and installation requirements against the datasheet for the specific model.

7. Drift, Calibration and Data You Can Still Trust

A dashboard is only as good as the last calibration behind it. As permanently installed instrumentation multiplies, the question shifts from “can we measure it?” to “is this number still true eighteen months later?”

Dew point is where this bites hardest

Chilled-mirror hygrometry is the reference method and is what a calibration laboratory uses – but it is poorly suited to permanent installation in a line carrying oil and particulate. Polymer capacitive sensors are the practical choice for continuous monitoring precisely because they tolerate condensation events and oil exposure.

Their long-term stability, and the interval at which they are recalibrated, is what determines whether the reading can still be trusted.

Traceability is the answer

Calibration against an ISO/IEC 17025 accredited reference, at a documented interval, with a certificate. Exchange calibration – a calibrated unit shipped out before the installed one is returned – has become the standard way to satisfy this without taking a monitoring point offline.

In regulated production the requirement goes further. Where compressed air data forms part of a batch record, FDA 21 CFR Part 11 expects electronic records to be attributable, time-stamped and tamper-evident, with an audit trail. That is now a specification line item for data loggers.

What a trustworthy measurement point needs:

Traceable calibration to an ISO/IEC 17025 reference

A documented recalibration interval

A certificate that survives an audit

A way to recalibrate without going dark

An audit trail where records support GMP decisions

8. Protocol-Native Instruments and Edge Gateways

“Connectivity” has become specific. The expectation now is that an instrument speaks Modbus RTU or Modbus TCP, MQTT or OPC UA natively, and that a gateway feeds a plant historian, an energy management system and a cloud dashboard at once – without a custom integration project.

The underlying change is that a compressed air sensor is no longer a local display with a 4–20 mA output. It is a data source inside an energy management system, judged on how easily its data reaches the place where decisions are made.

That last point about installation is worth dwelling on. The barrier to instrumenting a compressed air network has rarely been the cost of sensors. It has been production interruption. Installation methods that remove it change the economics of the whole project.

Three developments that follow:

Edge gateways buffer locally – a network outage costs connectivity, not data

Wireless transmission makes retrofit viable where cabling costs more than the instrument

Insertion probes fit through a ball valve under pressure – no line shutdown

9. Regulation Is the Near-Term Driver – Not Sustainability Reporting

Enterprises consuming more than 10 TJ a year (about 2.78 GWh) without a certified energy management system must complete an energy audit by 11 October 2026, repeated every four years. Above 85 TJ, a certified system – ISO 50001 satisfies this – is required by 11 October 2027. Both obligations come from Directive (EU) 2023/1791.

The directive does not name compressed air. It does not need to: an audit has to be based on measured, representative operational data, and in most manufacturing plants compressed air is one of the largest single electrical loads. It is also, characteristically, one of the least instrumented – which is why energy management of compressed air systems is where most audits find their savings.

What is not driving this

Corporate sustainability reporting is a weaker force than it looked two years ago. Directive (EU) 2026/470 – the Omnibus I amendment – entered into force on 18 March 2026 and narrowed CSRD scope to companies with more than 1,000 employees and net turnover above €450 million, both conditions together. The next reporting wave covers financial years beginning on or after 1 January 2027.

The German picture is more nuanced

The bill approved by the federal cabinet on 24 June 2026 amends both the EnEfG and the EDL-G. It would raise the EnEfG threshold for a mandatory energy management system from 7.5 to 23.6 GWh a year, and replace the EDL-G’s company-size test for energy audits with a consumption threshold of 2.77 GWh a year.

It is not yet law – parliamentary decisions are expected in autumn 2026. If it passes as drafted, fewer companies face a management-system mandate, while some SMEs previously exempt from auditing are pulled in. Either way, an audit needs measured data.

Looking further out

The GHG Protocol’s proposed Scope 2 revision – consultation closed 31 January 2026, publication expected in 2027 – would introduce hourly matching of renewable electricity purchases to consumption for certificate-backed claims. If it lands, when you consume electricity starts to matter as well as how much. Annual totals will not answer that; time-resolved consumption data will.

10. Where to Start: A Measurement Hierarchy

If you are instrumenting a compressed air system from a low base, the order matters more than the total spend.

Meter the compressor room. Flow and electrical power at station level give you specific power in kW per m³/min – the single number that benchmarks the whole installation.
Add pressure dew point downstream of the dryer. The cheapest early warning of an expensive quality failure, and in most plants the parameter that fails first.
Sub-meter your two or three largest consuming departments. Unattributed consumption and artificial demand surface here, and allocation changes behaviour in a way plant-level data never does.
Baseline non-production flow. Whatever the system draws when nothing is running is your leak figure – and unlike a one-off survey, it keeps reporting.
Add oil vapour and particle monitoring wherever the process specifies a purity class, rather than everywhere.

What a single leak actually costs

Take a 3.2 mm (1/8 in) equivalent orifice at 7 bar(g). The theoretical maximum discharge is about 43 m³/h of free air. Applying the discharge coefficient of 0.61 the US DOE specifies for a sharp-edged orifice, a realistic leak of that size passes closer to 26 m³/h.

Generating that costs roughly 2.8 kW of compressor power – about 19,400 kWh over 7,000 operating hours, or €2,900 a year at €0.15/kWh, from a single leak you can put your thumb over. A 6 mm equivalent orifice costs four times as much.

Flow and power derived from US DOE orifice data (Compressed Air Tip Sheet #3), which assumes 18 kW per 100 cfm and $0.05/kWh. Costs recalculated at a European industrial rate; the widely circulated dollar figures are usually quoted without the discharge coefficient, which overstates flow by around 40 %.

11. Where SUTO iTEC Stands on This

Every shift described above is one we are actively building for. SUTO iTEC has designed and manufactured its own compressed air instrumentation since 2005, with accredited calibration laboratories in Germany, Hong Kong and China – and since October 2025 as an independent brand within the Atlas Copco Group.

Behind the products sits the part that is easy to overlook: our own accredited laboratories, flow calibration to better than 0.5 % of reading, and an exchange-calibration service that ships a calibrated unit before the installed one comes out – so a monitoring point never goes dark.

None of this is finished. Continuous oil vapour measurement, acoustic leak imaging and time-resolved energy data are young, and the standards governing them are being rewritten as we go. That is exactly why we would rather publish what we know – including the limits of what continuous monitoring can and cannot certify – than wait for the picture to settle.

Already in the field:

S120 – residual oil to 0.001 mg/m³, an order of magnitude below Class 1

S532 + LMS – acoustic imaging from leak detection to documented repair

S332 – 150 Modbus channels, cloud upload, FDA 21 CFR Part 11 audit trail

S111 – electrical input and air flow in one dataset for specific power

S551 – portable logging for ISO 11011 and ISO 50001 assessments

FAQs – Compressed Air Measurement

What is the difference between m³/h, Nm³/h and scfm?

m³/h is the actual volume passing the meter at line conditions. Nm³/h and scfm are reference volumes: the same mass of air expressed as if it were at an agreed temperature and pressure, which is what makes two readings comparable.

The catch is that the reference conditions are not universal. “Normal” is usually 0 °C and 1013 mbar, but 20 °C and 1000 mbar is also widely used; ISO 1217:2009 Annex C uses 20 °C, 1 bar(a) and 0 % relative humidity. Always state the reference conditions alongside the figure – two meters quoting Nm³/h can differ by several per cent purely through convention.

What is the difference between pressure dew point and atmospheric dew point?

Pressure dew point (°Ctd) is the temperature at which water begins to condense out of the air at line pressure. Atmospheric dew point is the same air after it has expanded to ambient pressure.

Expansion lowers the dew point, so the atmospheric figure always looks better. For compressed air it is the pressure dew point that matters, because that is the condition the air is actually in inside your pipework – and it is what ISO 8573-1 water classes refer to.

How much straight pipe run does a compressed air flow meter need?

Enough for the flow profile to settle. Requirements are expressed in pipe diameters (D) and depend on both the meter principle and what sits upstream: a single bend needs far less than two bends in different planes, a reducer, or a partially open valve.

Insertion thermal meters are typically specified with a longer upstream run than downstream. Treat the figure on the datasheet as binding rather than the rule of thumb – installing in too short a run is one of the most common causes of a meter that reads consistently wrong and never gets trusted again.

Can a flow meter be installed without shutting down the compressed air line?

Yes, with an insertion probe fitted through a ball valve under pressure. The valve is welded or threaded into the pipe, the probe is inserted through it and sealed, and the line stays in service throughout.

This matters more than it sounds. The barrier to instrumenting a compressed air network is rarely the cost of the sensor – it is the production stop needed to fit it. Removing that changes the economics of the whole project.

How often should a dew point sensor be recalibrated?

There is no universal interval. What auditors expect is a documented interval that is justified by the criticality of the measurement, plus calibration traceable to an ISO/IEC 17025 accredited reference.

In practice, sensors on a quality-critical point after a desiccant dryer are checked more often than a sensor logging a refrigeration dryer for energy purposes. Exchange calibration keeps the measurement point live while the installed unit is away.

How often should compressed air quality be tested?

It depends on the sector. For food and beverage, BCAS Best Practice Guideline 102 calls for compressed air in direct or indirect contact with food to be tested at least twice a year, and after any maintenance that could affect air quality.

Pharmaceutical manufacturers generally set frequency by documented risk assessment rather than a fixed number. Continuous monitoring does not replace those tests – it tells you whether anything changed between them.

What is a good specific power figure for a compressed air station?

There is no single benchmark worth quoting, because specific power depends on discharge pressure, machine type, control mode, ambient conditions and how much of the station’s output is dryer purge rather than useful air.

The useful comparisons are internal: your station against its own trend, and your measured figure against the manufacturer’s data sheet for the same machine at the same pressure. A station drifting from 6.5 to 7.5 kW per m³/min tells you more than any industry average.

How do compressed air sensors connect to a SCADA or energy management system?

Most commonly over Modbus RTU or Modbus TCP, which nearly every historian, PLC and energy management platform can read directly. MQTT and OPC UA are increasingly used where data goes to a cloud platform or an IIoT broker, and 4–20 mA remains available for existing analogue inputs.

A gateway sitting between the sensors and the network handles the practical part: local buffering so a network outage costs connectivity rather than data, and feeding several destinations at once without a custom integration.

Sources

Every figure in this article traces back to a primary source.

Scoping a Compressed Air Measurement Project?

Preparing for an energy audit, or reviewing a purity specification against the coming ISO 8573-1 revision? Talk to a measurement expert – we typically reply within one business day.