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How Does A Laminar Flow Hood Work?

How Does A Laminar Flow Hood Work?

In settings and applications where a clean environment is essential, laminar flow hoods (LFHs) are a vital tool. Use of a LFH ensures a contamination-free workspace by generating a continuous flow of clean air to remove airborne particles. The system is built from components, each of which perform an important function.

How Does A Laminar Flow Hood Work?
The vertical laminar flow hood in use

Function and Components

Laminar flow hoods create a working environment that has unidirectional, laminar air flow. There are two primary types of laminar flow hood: vertical and horizontal. The choice between the two usually depends on the specific requirements of the work process.

It is important to note that while laminar flow hoods protect the sample or product from contamination, they do not protect the user from potential exposure to harmful substances.

The design of a laminar flow hood can vary, but all systems include these core components:

  • Fan — Draws air into the unit and pushes it through the filter.
  • Filter — Usually a high-efficiency particulate air (HEPA) or an ultra-low penetration air (ULPA) filter, this component traps airborne particles like dust and microbes.
  • Laminar Flow — The clean air moves in parallel lines at a uniform speed. In horizontal hoods, the flow is from back to front; in vertical hoods, it is from top to bottom.
  • Work Surface — The area where tasks requiring a clean environment take place.
  • Control System — This includes switches for operating the fan and lights, speed controls, and additional features.

These components work together to keep the air clean and maintain a sterile environment.

A Laminar Flow Hood in Action

Operating through a series of mechanical steps, a laminar flow hood removes particle contamination from the work environment. The fan pulls air from the room into the system. This air initially travels through a pre-filter to remove large particles. For finer filtration, air then passes through a HEPA or ULPA filter, which traps smaller particles and contamination. After filtration, the clean air is pushed into the work chamber in a laminar flow. It travels at a uniform speed from the filter to the front of the hood, removing and preventing any contamination.

Air flow movement through both a horizontal and a vertical laminar flow hood
Air flow movement and direction through both a horizontal and a vertical laminar flow hood

In a vertical hood, the air is pushed from a filter located at the top of the hood and flows downward onto the work surface. In contrast, a horizontal hood directs the airflow from a rear-mounted filter straight to the user.

Control systems are another vital aspect of the LFH's operation. Typically, this can include fan speed controls and environment monitoring sensors. These controls enable the user to customize the conditions inside the chamber according to their needs. Some models also come with additional features such as built-in ultraviolet (UV) lights for sterilization when the hood is not in use.

The performance and efficacy of a laminar flow hood are determined by the laminarity of the air flow, which can be influenced by several air flow properties, and the design of the system.


A laminar flow hood works by using a fan to draw air through specialized filters. These filters purify the air, which then flows smoothly over the work surface. This keeps contaminants away, ensuring a sterile environment for critical tasks. Essential components like the fan, filters, work surface, and control systems all work together to make this possible.

Laminar Flow Hood

Laminar Flow Hood

Contributing Authors

Reviewed by

Dr. Mary O'Kane

Application Scientist

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