Air Change


Air change is the amount of air required to completely replace the air in a defined space within a factory. Fresh air from the outdoor is cleaner in general and have more oxygen then the air within the factory. The rate of air change depends on the type of production process, factory which is highly heated, strong solvent or chemical smell may require a higher air change rate.

Air change rate is a unit of measurement of the amount of air moving through a defined space to the volume of the space in a specific time.

It is expressed as:

Air Change per Hour = Total Fresh Air Supplied (m3) per Hour / Volume of Workspace (m3)
Volume of Workspace = Length x Width x Height of the space
Air Change Rate determine how well a workspace is ventilated

The table below shows the recommended air change for various types of work processes.


Recommended Design Air At 4 m Height

WorkspaceHeat generation from process (little)Heat generation from process (medium)Heat generation from process (high)Air Change Rate
Platic Injection Molding 30 ~ 40
Plastic bags & Film Manufacturing 40
Plastic Extrusion & Pultrusion 30
Plastic Label Printing 30 ~ 40
Rubber Label, Molding, Calendering 40
Rubber Milling 40
Rubber Dipping 40
Metal Machining, Milling, Pressing 25
Metal Electro-plating 30 ~ 40
Metal Welding 30 ~ 40
Metal Forming 25 ~ 30
Spraying 30 ~ 40
Food Cooking, Steaming 40
Food Sterilizering 40
Food Packing, Canning 30
Quality Control 30
Assembly & Sorting Line 30
Packing Area 25~30
Staff Canteen 25~30

1. Outside conditions based on ambient dry-bulb temperatures between 30°C to 38°C, RH 40% to 60%.
2. Criteria established here are based on Waterline's experience and subject to change with new findings.
3. Please refer to Waterline's sales for other areas not specified above.