The air flow organization form of a laminar flow hood is the core factor determining its cleaning effect, operational convenience and protective performance. It mainly works by the fan driving the air to be processed by the filtration system and then form a stable air flow barrier in the working area in a specific direction. The common forms of air flow organization can be divided into two major categories: horizontal laminar flow and vertical laminar flow. Some special models will combine the characteristics of both or add auxiliary air flow designs, as follows:
1. Horizontal Laminar Flow Clean Bench
Airflow direction: The filtered clean air is blown out horizontally from the rear side (or left/right side) of the workbench perpendicularly to the operating surface, flows along the workbench surface to the operator’s side (or front side), and finally returns from the edge or bottom of the workbench surface.
Features
The airflow directly covers the entire operation surface, providing a more direct effect on the cleanliness and protection of the surface. It is suitable for operations with high requirements for the cleanliness of the workbench (such as the assembly of electronic components and the debugging of precision instruments).
As the airflow flows towards the operator, if handling samples with biological hazards (such as pathogenic microorganisms), it may increase the operator’s exposure risk. Therefore, it is not suitable for scenarios with high requirements for biosafety protection.
Applicable scenarios: Electronic manufacturing, optical instrument assembly, non-pathogenic microorganism experiments, food packaging, etc.
Ii. Vertical Laminar Flow Clean Bench
Airflow direction: The filtered clean air is blown vertically downward from the top of the workbench, flows over the operating surface, and then is discharged through the return air channels below or around the surface.
Features
The airflow flows from top to bottom to form an “air curtain”, which can effectively prevent external pollutants from entering the operation area and at the same time reduce the diffusion of pollutants generated during the operation process (such as dust brought by the operator’s breathing and movements).
If designed as the “full exhaust” mode (i.e., clean air flows through the operation area and is directly discharged outdoors without being recycled), it can reduce the risk of operators coming into contact with harmful samples, and thus is more suitable for biosafety protection scenarios.
Subcategory:
Open vertical laminar flow: Top air outlet, bottom or side air return, suitable for general aseptic operations (such as cell culture, preparation portioning).
Biosafety vertical laminar flow: Based on vertical airflow, a negative pressure design is added to create a pressure difference between the operation area and the external environment. The airflow is discharged after high-efficiency filtration, which can protect against low-level biological hazards (such as P2-level laboratories).
Applicable scenarios: Microbiological experiments, cell and tissue culture, pharmaceutical preparation production, clinical testing, biological product preparation, etc.
Iii. Other derivative forms
Composite airflow type: A few workbenches combine the characteristics of horizontal and vertical airflows, for instance, vertical airflows are dominant at the top, supplemented by horizontal airflows at the rear to enhance local cleanliness. However, their structure is relatively complex and they are less applied.
The combination of unidirectional flow and turbulent flow: In some large workbenches, unidirectional laminar flow (horizontal or vertical) is adopted in the core operation area, while turbulent flow is used to assist in purification in the peripheral areas, balancing cleanliness and energy consumption. However, the core still takes unidirectional flow as the core.
When making a selection, key attention should be paid to factors such as the harmfulness of the operating object (whether the operator needs protection), the cleanliness grade requirements, and the convenience of operation (for example, vertical air flow may block the view, while horizontal air flow is more convenient for hand operation).
1. Horizontal Laminar Flow Clean Bench
Airflow direction: The filtered clean air is blown out horizontally from the rear side (or left/right side) of the workbench perpendicularly to the operating surface, flows along the workbench surface to the operator’s side (or front side), and finally returns from the edge or bottom of the workbench surface.
Features
The airflow directly covers the entire operation surface, providing a more direct effect on the cleanliness and protection of the surface. It is suitable for operations with high requirements for the cleanliness of the workbench (such as the assembly of electronic components and the debugging of precision instruments).
As the airflow flows towards the operator, if handling samples with biological hazards (such as pathogenic microorganisms), it may increase the operator’s exposure risk. Therefore, it is not suitable for scenarios with high requirements for biosafety protection.
Applicable scenarios: Electronic manufacturing, optical instrument assembly, non-pathogenic microorganism experiments, food packaging, etc.
Ii. Vertical Laminar Flow Clean Bench
Airflow direction: The filtered clean air is blown vertically downward from the top of the workbench, flows over the operating surface, and then is discharged through the return air channels below or around the surface.
Features
The airflow flows from top to bottom to form an “air curtain”, which can effectively prevent external pollutants from entering the operation area and at the same time reduce the diffusion of pollutants generated during the operation process (such as dust brought by the operator’s breathing and movements).
If designed as the “full exhaust” mode (i.e., clean air flows through the operation area and is directly discharged outdoors without being recycled), it can reduce the risk of operators coming into contact with harmful samples, and thus is more suitable for biosafety protection scenarios.
Subcategory:
Open vertical laminar flow: Top air outlet, bottom or side air return, suitable for general aseptic operations (such as cell culture, preparation portioning).
Biosafety vertical laminar flow: Based on vertical airflow, a negative pressure design is added to create a pressure difference between the operation area and the external environment. The airflow is discharged after high-efficiency filtration, which can protect against low-level biological hazards (such as P2-level laboratories).
Applicable scenarios: Microbiological experiments, cell and tissue culture, pharmaceutical preparation production, clinical testing, biological product preparation, etc.
Iii. Other derivative forms
Composite airflow type: A few workbenches combine the characteristics of horizontal and vertical airflows, for instance, vertical airflows are dominant at the top, supplemented by horizontal airflows at the rear to enhance local cleanliness. However, their structure is relatively complex and they are less applied.
The combination of unidirectional flow and turbulent flow: In some large workbenches, unidirectional laminar flow (horizontal or vertical) is adopted in the core operation area, while turbulent flow is used to assist in purification in the peripheral areas, balancing cleanliness and energy consumption. However, the core still takes unidirectional flow as the core.
When making a selection, key attention should be paid to factors such as the harmfulness of the operating object (whether the operator needs protection), the cleanliness grade requirements, and the convenience of operation (for example, vertical air flow may block the view, while horizontal air flow is more convenient for hand operation).
