Vertical and horizontal laminar flow cabinets.

How to know which hood is right for you.

Do I need a horizontal or vertical laminar flow hood?

As one of Ireland’s leading suppliers of laboratory equipment & clean air technology, our team is asked a lot of questions relating to the equipment we supply, the safe servicing requirements, the mechanics of lab equipment, filters etc. 

One question we are asked a lot is whether a vertical or a horizontal laminar flow is going to be the right fit for a specific laboratory environment. We’ve summarised the pro’s and con’s of each so you can make an informed decision.

“A LAMINAR flow system is vital in the control of particulate contamination. Laminar airflow can be described as an entire body of airflow with steady, uniform velocity.”

What is a Laminar Flow Cabinet (Hood)?

A LAMINAR flow system is vital in the control of particulate contamination. Laminar airflow can be described as an entire body of air flow with steady, uniform velocity. 

Within a Laminar Flow Cabinet air is initially drawn through an easy-change, high-quality EU4 pre-filter to remove all gross particulate. All air then passes through the fan system, before being pushed through a H15 ULPA filter which removes 99.9998% of all particles >0.12 μm in size. 

This in turn guarantees an ISO Class 3 (FED Class 1) for Vertical Laminar Flow (VLF) and ISO Class 4 (FED Class 10) for Horizontal Laminar Flow (HLF), particle-free working environment and provide the best product protection.

The cabinet is enclosed on three sides and constant positive air pressure is maintained to prevent the intrusion of any contaminated air.

Vertical Laminar Flow

Vertical Laminar Flow: Room air (in red) enters the system from above the HEPA filter; 99.997% particle-free air (in green) is forced downward toward the work surface.

  • Greater Operator Protection.
  • Cabinet not as deep: requires less floor/worktop space.
  • Suitable for compounding sterile products.
  • Safety: air will not blow directly at operator and sash provides a barrier.
  • Top-mounted filter ensures easy access.
  • Less turbulence from air striking large objects or equipment.
  • Less cross-contamination of items positioned on the work surface.
  • Extended overhead clearance means changing filters or servicing may require a step-ladder.
  • Cannot place items or hands on top of other items as this will obstructs airflow.
  • Increased turbulent effect of air striking the work surface.

Horizontal Laminar Flow

Horizontal Laminar Flow: Room air (in red) enters the system from behind the HEPA filter; 99.997% particle-free air (in green) is forced in a back-to-front direction across the work surface.

  • Greater Product Protection.
  • Reduced turbulent effect of air striking work surface.
  • No sash: easier to work and position equipment, but air blows directly on operator.
  • Hands and gloves are generally less contaminating since they’re downstream
    of the sample.
  • Large samples obstruct laminar air flow, may contaminate downstream samples.
  • Blows fumes and/or powders in operator’s face.
Most contamination-sensitive environments require laminar flow as it forces particles in a uniform direction, from the cleanest area under the filter face to the exit area, which is generally the working aperture. This design ensures that the cleanest area will always be the upstream area closest to the filter face. Work is generally done in this clean zone, as far as possible from obstructions that create turbulence.

The market leader in clean air solutions

Vertical Laminar Flow Cabinets are often chosen because they resemble, on a small scale, the design of a Cleanroom, in which fan/filter units are typically positioned in the ceiling. By directing the laminar flow downward, Vertical Laminar Flow reinforces the effect of gravity and sweeps particles out of the enclosure, generally through a front access area. Micro-contaminants may not have substantial mass, but most particles do eventually settle on a work surface or the floor of a room, and vertical flow helps get them there faster.

If sterile or particle-sensitive processes are performed in a clean, sterile zone midway between the work surface and the filter face, a Vertical Laminar Flow Cabinet is generally acceptable. One such operation is sterile compounding, in which injectable or sterile packages are prepared above, not on, the work surface. As long as hands and other contamination sources move up and down, not sideways above a sample, sensitive materials will remain clean.

Finally, consider the effects on operators of air exiting the Laminar Flow Cabinet. Although Horizontal Laminar Flow, with air travelling from the rear of the cabinet and exiting through the front opening, may not encounter large obstructions inside the cabinet, it does eventually encounter the person performing the work. Substances, such as soldering fumes or fine powders, may be blown into the operator’s face. While this collision may not compromise the laminar flow where work is performed, it may pose a health risk. In such cases, vertical flow is preferable as it offers greater operator protection.

Do you have a question relating to Laminar Flow cabinets?

If you have a question that we didn’t cover off here, drop a comment below and we would be thrilled to add it to our next FAQs post.

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