A pneumatic breaker needs both the specified airflow and the specified pressure at the tool while it is working. CFM, L/s and m³/min describe air volume per unit time; PSI, bar and MPa describe pressure. They are related by the compressor system, but they are not interchangeable. A compressor can show adequate pressure while delivering too little sustained flow, or advertise ample flow at a pressure that does not match the breaker rating.
For procurement and field checks, treat the breaker data sheet as the authority. Record the stated air consumption, reference pressure, inlet size and duty condition together. Then compare them with the compressor’s delivered-air rating at the same pressure, the number of tools that may run simultaneously, and the losses through hoses, couplings and treatment equipment. This guide explains the terms and the comparison method; it does not replace the breaker or compressor manufacturer’s operating limits.
The short answer: read flow and pressure as a pair
| Specification | What it tells the buyer | What it does not prove |
|---|---|---|
| Air consumption: CFM, L/s or m³/min | The volume rate the breaker uses at a stated condition | That the required pressure reaches the tool inlet |
| Pressure: PSI, bar or MPa | The pressure condition at which the tool is intended to operate | That the compressor can sustain the required volume |
| Compressor FAD or delivered flow | Air actually delivered under the declared rating method | What remains after every site loss unless the test point is stated |
| Receiver or tank volume | Short-term storage that can smooth demand | Continuous capacity for a breaker used for long periods |
| Motor power or horsepower | One compressor design input | Delivered airflow at the breaker’s required pressure |
The practical rule is simple: compare flow with flow and pressure with pressure at declared conditions. Never approve a breaker–compressor match from horsepower, tank volume or an unloaded pressure gauge alone.
What CFM, L/s and m³/min mean
All three units express volumetric airflow. CFM means cubic feet per minute, L/s means litres per second, and m³/min means cubic metres per minute. A buyer may receive the breaker specification in one unit and the compressor quotation in another, so conversion is often necessary.
- 1 L/s is approximately 2.119 CFM.
- 1 m³/min is approximately 35.315 CFM.
- 1 m³/min equals 1,000 L/min, or approximately 16.667 L/s.
These conversions align the unit scale only. They do not correct for different reference conditions, pressure points or rating methods. “80 CFM” on one document and “38 L/s” on another are numerically close after conversion, but the comparison is valid only if both figures refer to compatible conditions.
Why the reference condition matters
Air is compressible. The physical volume occupied by a given mass of air changes with pressure and temperature. Compressor makers therefore state airflow using a defined rating convention, commonly a free-air or standard-condition basis. The exact terminology and reference conditions can vary among documents and regions.
Ask whether a figure is inlet volume, displacement, free air delivery, actual delivered flow or consumption at the tool. If the document does not define the basis, do not silently assume that two figures are directly comparable. Request the test condition or manufacturer confirmation.
What PSI, bar and MPa mean
Pressure describes force per unit area. Common pneumatic-tool units include pounds per square inch (PSI), bar and megapascal (MPa). Useful approximate conversions are:
- 1 bar is approximately 14.504 PSI.
- 1 MPa equals 10 bar.
- 1 MPa is approximately 145.038 PSI.
A breaker’s pressure rating should be interpreted at the location named by the manufacturer. Compressor discharge pressure, regulator outlet pressure and pressure at the moving tool inlet are not automatically the same. Long or undersized hoses, restrictive couplings, clogged filters, lubricators, manifolds, leaks and simultaneous users can all create a difference between source pressure and tool-inlet pressure.
FAD, displacement and delivered airflow are not the same label
Free air delivery (FAD) is a compressor capacity term intended to express delivered airflow referenced to inlet or agreed standard conditions. It is more useful for matching than motor power alone. However, the buyer still needs the pressure at which the FAD is available and the rating standard or test basis.
Displacement is a theoretical swept-volume figure for the compression element. It can be higher than usable delivered flow because real compressors have internal losses, leakage, heating and control behavior. If a supplier quotes only displacement, request FAD or another verified delivered-air figure at the required working pressure.
Do not confuse the compressor’s capacity rating with the air that reaches the tool after the distribution system. The breaker can only use what arrives at its inlet under load.
Why a pressure gauge can look normal while the breaker is weak
A static gauge reading is taken when air use is low or stopped. Under that condition, the hose network can charge to the regulator or compressor pressure even if it cannot pass enough air for continuous breaking. When the trigger opens, the breaker consumes air and the dynamic pressure may fall.
If the breaker starts strongly and then becomes weak, or one tool performs normally while a second simultaneous tool slows both, the supply network deserves investigation. The symptom does not by itself prove a compressor fault; restrictions, leaks, icing, poor lubrication and internal breaker wear can produce similar effects. Use a controlled sequence:
- Confirm the breaker’s stated flow and pressure requirements from its current data sheet.
- Measure or observe pressure at the point specified by the manufacturer, under the intended load where the approved procedure allows.
- Inspect hose length and internal diameter, couplings, valves, filters, lubricator and manifold for restrictions or leakage.
- Run one breaker alone, then repeat the defined check with the planned simultaneous load.
- Record the compressor operating state, ambient condition and any pressure recovery or control cycling.
- If supply remains within specification but performance is poor, continue with breaker lubrication, chisel fit and internal-wear checks.
Only trained personnel should connect test instruments. Isolate, depressurize and secure the system before changing hoses, gauges or fittings, and follow the compressor and breaker manuals.
Continuous demand, intermittent use and duty cycle
Duty cycle describes how much of a time period a tool or compressor is expected to operate. A small chipping task may involve short trigger periods separated by repositioning. Pavement or quarry breaking can involve much longer loaded periods. The same nominal breaker can therefore create different average demand on two jobsites.
For a continuously used breaker, receiver storage cannot substitute for sustained compressor delivery. A tank can support a short burst, but pressure will fall if average demand exceeds replenishment. Compressor design also matters: its permitted load cycle, cooling and ambient derating must suit the planned work. Do not invent a universal margin. Use the compressor manufacturer’s sizing method and project conditions.
As an external reasonableness check—not a substitute for the exact tool data sheet—VMAC’s air-tool guide lists loaded-flow ranges of 64–70 CFM for a 60 lb pavement breaker and 62–85 CFM for a 90 lb pavement breaker. The spread itself is the useful lesson: weight class does not define one universal consumption figure. Model-specific documentation controls.
How to total simultaneous pneumatic-breaker demand
When multiple tools can run together, begin with the sum of their declared consumption at compatible conditions. Then account for the compressor maker’s permitted operating margin, site derating and distribution losses. Do not multiply a tool’s intermittent average by the number of operators if the real worst case is that several breakers run continuously at once.
| Planning question | Evidence to collect | Common error |
|---|---|---|
| How many tools can run together? | Crew plan and maximum simultaneous count | Using total tools owned or assuming only one will run |
| What does each tool consume? | Model data sheet with reference pressure | Using a generic internet chart as the purchase specification |
| What can the compressor deliver? | FAD or verified delivered flow at the required pressure | Comparing motor horsepower or tank size |
| What is lost before the tool? | Hose ID and length, fittings, manifold, leaks and treatment devices | Assuming discharge pressure equals inlet pressure |
| What changes at the site? | Altitude, temperature, maintenance state and operating schedule | Using a sea-level brochure figure without review |
A buyer’s specification-comparison worksheet
Use one row per breaker model and one row per compressor option. Preserve the supplier’s original units, add converted units in separate columns, and record the source document revision.
- breaker model and application;
- rated air consumption and unit;
- pressure associated with that consumption;
- whether consumption is average, loaded, maximum or another declared condition;
- air inlet thread or coupling and required hose ID;
- compressor make and model;
- FAD or delivered flow at the required pressure;
- maximum simultaneous breakers;
- hose internal diameter, length and routing;
- filters, separator, lubricator, manifold and coupling details;
- ambient temperature and site altitude supplied to the compressor vendor;
- test method and acceptance point at the tool inlet;
- spare hoses, couplings and lubricator requirements.
For breaker operating principle context, read How Does a Pneumatic Breaker Work?. For the broader equipment decision, use the published pneumatic breaker selection guide.
Common specification mistakes
- Comparing CFM with PSI. One is flow; the other is pressure.
- Converting units but ignoring conditions. Arithmetic does not normalize rating methods.
- Buying from horsepower. Power alone does not state delivered flow at the required pressure.
- Using static pressure as proof. A charged hose can show pressure before the tool opens.
- Treating a receiver as continuous capacity. Stored air is temporary.
- Ignoring simultaneous use. The worst credible overlap governs the distribution plan.
- Assuming every breaker of one weight uses the same air. Valve, piston, frequency and design differ by model.
- Forgetting the test point. A reading at the compressor is not automatically a reading at the breaker.
Frequently asked questions
Is CFM more important than PSI for a pneumatic breaker?
Neither can replace the other. The breaker needs adequate airflow at the required pressure. Match both values at compatible reference conditions.
Can a compressor show the correct PSI and still be too small?
Yes. Static pressure can recover while the breaker is stopped. If the compressor or distribution path cannot sustain flow, dynamic pressure may fall when the tool operates.
What is the difference between CFM and SCFM?
CFM is a volumetric-flow unit; SCFM usually indicates that the volume has been referenced to stated standard conditions. Those conditions are not identical in every document, so confirm the definition before comparing ratings.
Should I add the CFM of two breakers?
If both can operate simultaneously, start with the sum of their model-specific consumption figures at compatible conditions. Then apply the compressor manufacturer’s sizing and derating method rather than an unsupported universal percentage.
Does a larger air tank let a small compressor run a breaker continuously?
No. A larger receiver can extend a short burst or reduce cycling, but continuous operation still requires average compressor delivery to meet average system demand.
Confirm the air-demand basis before requesting a quotation
A technically useful inquiry includes the breaker model, required pressure, air-consumption basis, compressor FAD at that pressure, simultaneous tool count, hose layout, altitude, ambient temperature and working pattern. If any value is missing, mark it as unknown rather than substituting a generic chart.
PerfoMax can review a breaker inquiry from the actual job and air-supply data. Send the material, work position, model or desired tool class, available compressor rating, hose information, quantity and destination through the Request a Quote page. The commercial route can then be checked without forcing an unverified product match.
Technical references
- Chicago Pneumatic: How to Size an Air Compressor — explains why both CFM and pressure are required.
- Atlas Copco: Compressor Sizing Guide — describes airflow/FAD and continuous-demand considerations.
- VMAC: Air Tool Consumption Guide — provides model-class reasonableness ranges and emphasizes checking manufacturer specifications.