30 m × 20 m × 6 m At 8 ACH
- Volume
- 30 × 20 × 6 = 3,600 m³
- Hourly Flow
- 3,600 × 8 = 28,800 m³/h
- Per Minute
- 28,800 ÷ 60 = 480 m³/min
- Imperial
- 28,800 ÷ 1.699 ≈ 16,951 CFM
Industrial Ventilation Calculation Guide
Industrial Exhaust Fan Sizing Calculator: CFM, m³/h And ACH
Calculate a first-pass room airflow target from building volume and a project-defined air-change rate—then carry pressure, replacement air and the actual process into fan selection.
Imperial FormulaCFM = L × W × H × ACH ÷ 60
Metric Formulam³/h = L × W × H × ACH
Conversion1 CFM ≈ 1.699 m³/h
Selection BasisAirflow + Static Pressure
Direct Answer
How Do You Size An Industrial Exhaust Fan?
For a first-pass general-ventilation target, calculate the effective room volume and multiply it by an air-change rate established for the project. In imperial units, divide by 60 to obtain CFM. In metric units, the same multiplication gives m³/h.
The result is the amount of air the room calculation asks the system to move. It is not yet a fan model. A real fan must deliver that airflow at the resistance created by its guard, louver, shutter, backdraft damper, duct, bends, filters and discharge arrangement, while the building supplies enough replacement air.
ACH is an input—not a universal recommendation generated by this page. Establish it from the actual operating objective, applicable design basis, process information and qualified project review. A hazardous source may need local capture rather than general room dilution.
Method and source links reviewed 3 October 2026 · Calculator rounds displayed results but uses unrounded values internally
Interactive First Pass
Industrial Exhaust Airflow Calculator
Enter one zone at a time. The result is a target air volume for scoping—not a final fan count or a substitute for a pressure-based selection.
01
Building Volume And ACH
Illustrative default only: 8 ACH is used to demonstrate the arithmetic. It is not an AirMoveX recommendation for a building type.
Preliminary target airflow
28,800 m³/h
≈ 16,951 CFM
- Calculated volume
- 3,600 m³
- Air per minute
- 480 m³/min
- ACH source
- Project design input
- Next check
- Static pressure + replacement air
Valid first-pass room-airflow result. Continue with the duty-point checks below.
Worked Example
From A 3,600 m³ Workshop To A Flow Target
This example verifies the calculator step by step. The ACH value is illustrative, not a recommendation for a specific process.
Confirm The Effective Volume
Use the air volume that is actually being served. Separate enclosed rooms, mezzanines or independently controlled zones when one gross rectangle would hide the real air path.
Document Where ACH Came From
Record the process basis, owner criterion, code reference or qualified designer that supplied the air-change input. A search snippet is not a design basis.
Build The System Resistance
List every guard, louver, shutter, damper, duct section, bend, transition, filter and discharge fitting that the selected fan must overcome.
Verify The Complete Operating Point
Match the target airflow and pressure on a fan curve, then check replacement air, sound, environment, controls, electrical input and installation.
Do Not Size Hazardous Source Control By Room ACH Alone
Fumes, vapors, airborne toxic material and combustible dust can require capture at the source, engineered transport velocity, air cleaning, discharge controls and application-specific equipment. Use qualified ventilation and safety design for those cases.
Duty Point
Why The Calculation Is Not The Fan Selection
A fan operates where its performance curve meets the resistance of the installed system. The same fan can deliver different airflow in different installations.
Static Pressure
Add the resistance of all components at the intended flow. Ask for performance at that pressure—not just a maximum or free-air number.
System Effect
Poor inlet or discharge geometry can create non-uniform flow and additional losses that a simple component total misses.
Replacement Air
Exhausted air must enter the building somewhere. An undersized or obstructed inlet path can increase negative pressure and reduce delivered flow.
Operating Conditions
Temperature, density, corrosion, contaminants, sound, motor and controls determine whether a platform is appropriate for the service.
Engineering reference: AMCA's system-effect article describes the causes and performance impact of inlet and outlet conditions and outlines ways to minimize or avoid those losses.
Read “Mitigating System Effect To Optimize Fan Performance And Efficiency”Selection Inputs
Carry These Eight Checks Into The Quote
A comparable quote states the duty and boundaries. It does not replace missing system inputs with an unexplained fan size.
| Input | What To Provide | Why It Changes Selection |
|---|---|---|
| Ventilation objective | General heat, moisture, odor, dilution or defined source-capture duty | Determines whether a room ACH calculation is even the right method. |
| Zone geometry | Length, width, effective height, partitions, openings and adjacent spaces | Defines volume and whether the project needs separate controlled zones. |
| Design airflow | Required CFM or m³/h and the documented source of the ACH or process flow | Creates the target that the complete system must deliver. |
| Pressure path | Guard, louver, shutter, damper, duct, bends, transitions, filters and discharge | Moves selection from a free-air figure to a real duty point. |
| Replacement air | Inlet locations, net free area, controls and expected building pressure | Prevents starvation, unintended door forces and short-circuit air paths. |
| Air and environment | Temperature, humidity, corrosion, contaminants and outdoor exposure | Changes materials, motor, protection, cleaning and safety requirements. |
| Electrical and controls | Voltage, phase, frequency, speed control, staging, sensors and interlocks | Defines compatible motors, controller scope and operating sequence. |
| Commercial scope | Quantity, accessories, certification, drawings, packing, destination and delivery basis | Makes supplier offers comparable and reduces post-order scope gaps. |
AirMoveX Reference Range
Screen Platforms Only After The Duty Is Defined
These catalog values are preliminary references. Final model, airflow at pressure, electrical configuration and project scope are confirmed in the quotation.
| Platform | Published Sizes | Catalog Air-Volume References | Use In Screening |
|---|---|---|---|
| AXE-E FRP Exhaust | 26, 36 and 42 in | 389, 471 and 546 m³/min 23,340–32,760 m³/h by unit conversion | Corrosion-sensitive wall-exhaust projects, subject to compatibility and verified duty conditions. |
| AXE-SQ Galvanized Exhaust | 30, 37, 44, 50 and 56 in | 435, 667, 774, 1,005 and 1,037 m³/min 26,100–62,220 m³/h by unit conversion | Square wall-opening projects where the galvanized platform and service conditions fit. |
Catalog Data Boundary
The figures above reproduce the current AirMoveX catalog dataset and convert m³/min to m³/h by multiplying by 60. They do not establish delivered airflow at an unstated pressure. Request the applicable performance evidence for the quoted model and operating point.
Method Sources
Primary References And Use Boundary
These sources support the ventilation-system context. Project requirements and local rules still determine the actual design.
OSHA Technical Manual, Section III, Chapter 3: an overview of industrial ventilation, including general and local exhaust concepts, hoods, ducts, air cleaners and fans.
Open The OSHA Ventilation ChapterOSHA 29 CFR 1910.94: ventilation requirements for specific operations such as abrasive blasting, grinding, polishing and spray finishing.
Open OSHA 1910.94AMCA system-effect article: explains why actual fan performance depends on inlet and outlet conditions as well as the selected equipment.
Open The AMCA ArticleSizing Questions
Industrial Exhaust Fan Sizing FAQ
The short answers are designed for quick extraction; the calculator and duty-point sections provide the working method.
How do I calculate exhaust fan CFM from room size?
Multiply length, width and height in feet, multiply the result by the project ACH, then divide by 60. CFM = L × W × H × ACH ÷ 60. Treat the answer as a preliminary airflow target, not a final fan model.
What ACH should I use?
Use the value established by the actual ventilation objective, applicable design basis, process information, owner criteria and qualified project review. There is no universal ACH that this page can safely assign to every factory, farm or workshop.
Does published fan airflow equal installed airflow?
Not automatically. Confirm the test condition and the fan's performance at the required pressure. Guards, shutters, dampers, ducts, bends, filters, system effect and replacement-air restrictions can reduce the installed flow.
How much replacement air is required?
The inlet path must supply approximately the volume being exhausted, subject to the intended pressure balance and controls. Check net free area rather than gross opening size, and prevent short-circuiting from an inlet directly to an exhaust opening.
Can I use this calculator for hazardous fumes or combustible dust?
No room calculator can replace source-capture and safety engineering. Hazardous fumes, vapors or combustible dust require contaminant-specific design, materials, controls, discharge arrangements and applicable regulatory review.
How do I estimate the number of exhaust fans?
After the system pressure is known, divide the required total airflow by one fan's verified airflow at that duty point and coordinate staging, redundancy and layout. Do not base the count on an unrelated maximum or free-air number.
Turn The Result Into A Comparable Quote
Send the building dimensions, the source of the ACH or process-flow target, the complete pressure path, replacement-air plan, environment, electrical supply, destination and required documents. AirMoveX will screen the AXE-E and AXE-SQ ranges against that scope.
Request An Exhaust Fan Review