Introduction
Factory ventilation helps maintain a safe and comfortable working environment by removing excess heat, dust, fumes, and stale air while bringing in fresh air. The right ventilation system improves air quality and supports efficient factory operations. Most factories use a combination of general ventilation to circulate fresh air throughout the building and local exhaust ventilation to remove contaminants directly from their source.
Why does the calculation matter?
Because a badly sized fan either doesn’t solve the problem or wastes money every month. Too small, and heat and fumes stay on the floor. Too big, and you pay for power you don’t use and put up with noise and drafts. Ten minutes of calculation before you buy is far cheaper than swapping fans after installation.
Do you need fans, or is natural ventilation enough?
You need fans when doors, windows and roof vents can’t keep the space cool or clean on their own. Natural ventilation relies on wind and rising hot air, so it is unreliable on still days and does very little in closed or machine-heavy buildings. If your shop floor gets hot, smelly or dusty even with every opening available, mechanical ventilation is the answer.
Step 1: Calculate Factory Volume
Multiply the factory’s length, width, and average height.
Volume (m³) = Length × Width × Height
Step 2: Determine Air Changes Per Hour (ACH)
The required ACH depends on the factory’s activities.
| Factory Type | Typical ACH |
|---|---|
| Warehouses | 2–6 |
| General manufacturing | 6–10 |
| Machine shops | 6–12 |
| Welding areas | 10–20 |
| Furnaces and hot processes | 15–30 |
These are estimates. Actual requirements depend on applicable standards and working conditions.
Step 3: Calculate Required Airflow
Multiply the factory volume by the required ACH.
Airflow (m³/h) = Volume × ACH
Example: A factory measuring 40 × 25 × 6 metres has a volume of 6,000 m³. At 10 ACH, it needs 60,000 m³/h of airflow.
Step 4: Consider Heat
If heat is the main concern, calculate the airflow needed to remove excess heat and compare it with the ACH result.
Approximate airflow (m³/h) = 3,000 × Heat load (kW) ÷ Temperature rise (°C)
Step 5: Check Static Pressure
Ducts, filters, and grilles can reduce airflow. Choose a fan based on its performance at the required system pressure.
- Axial fans: General ventilation with low resistance.
- Inline duct fans: Ducted ventilation.
- Centrifugal blowers and plug fans: Systems with higher resistance.
Step 6: Check Power Requirements
Fan power depends on airflow, pressure, and efficiency. Choose a suitable motor based on the fan’s operating requirements.
Step 7: Plan Fresh-Air Intake
Ensure enough fresh air can enter the factory to replace exhausted air. Position intake and exhaust openings to promote effective air circulation.
Which type of fan should you use?
Match the fan to the resistance in your system: axial for open, high-volume jobs, centrifugal for anything with ducts, filters or fumes.
| Fan type | Best for | Pressure |
|---|---|---|
| Axial fans | General factory ventilation, large airflow through wall openings | Low |
| Roof extractors | Letting hot air out through the roof of sheds and plants | Low |
| Inline duct fans | Ducted ventilation and fresh air supply | Medium |
| Plug fans | Ducted systems and air handling with higher resistance | Medium to high |
| Centrifugal blowers | Fume and dust extraction, filters, hoods | High |
What mistakes should you avoid?
The five most common ones are easy to fix if you know about them before you buy.
- Using the fan’s free-air rating instead of its airflow at your system pressure.
- Skipping the safety margin.
- Forgetting the replacement air.
- Using one ACH value for every area of the factory.
- Letting dust build up on blades and filters, which slowly cuts airflow.
How do you keep the system working well?
Clean fan blades and filters regularly, and inspect bearings, belts, and vibration on a set schedule. Dust buildup can reduce airflow and fan performance over time. Follow a regular maintenance schedule to keep your industrial fans operating efficiently and reliably.
Need help sizing fans for your factory?
Since 2004, Eyyani Electric Machines has been manufacturing industrial fans and blowers in Bengaluru, India. With expertise in industrial air-moving solutions, we focus on quality, reliable performance, and efficient airflow. Our products come with a 1-year manufacturing warranty. Share your factory dimensions, airflow requirements, and duct details with our team to find the right fan or blower for your application.
Factories typically need 6–10 air changes per hour (ACH) for general manufacturing and 10–30 ACH for hot or fume-heavy areas. Actual requirements depend on the process and applicable ventilation standards.
Use axial fans and roof extractors for high airflow with low resistance, and centrifugal blowers or plug fans for systems with higher resistance from ducts, filters, or hoods.
Industrial fans may lose airflow due to dust buildup, imbalanced blades, worn bearings, insufficient fresh-air intake, or incorrect fan sizing. Regular cleaning and performance checks help identify and fix these issues.
