What’s the Difference Between Horizontal vs. Vertical Laminar Flow Hoods?

What’s the Difference Between Horizontal vs. Vertical Laminar Flow Hoods?

Laminar flow hoods play a crucial role in minimizing contamination for sensitive products. In this blog, we’ll compare horizontal vs. vertical laminar flow hoods, providing insights into their configurations, pros, and cons. 

Whether you’re working with IV solutions, tissue culture, optics, or microelectronics, understanding these flow hoods is key to a contaminant-free workspace. Join us as we navigate the differences to help you make informed decisions for your cleanroom requirements.

Understanding Laminar Airflow and Its Crucial Role in Cleanrooms

Laminar airflow is air that constantly moves at the same speed in the same direction. In cleanrooms, a vertical laminar flow room is an enclosure where 100% of the ceiling provides filtered air downwards from the ceiling. Because of the 100% filter coverage, it creates an ultra-clean environment. But it’s much easier to achieve laminar flow in a smaller space, as equipment, personnel, and movement in a room cause turbulence that disturbs airflow.

A laminar flow hood is a device or enclosure commonly used as an ultra-clean workbench in laboratory applications. Filtered air sweeps particles in a uniform speed and direction from the hood’s most treated area (the filter) to its exit area.

Cleanroom airflow uniformity and laminar flow hoods are essential to ensuring that sensitive products placed under the hood are always upstream and, therefore, suffer little to no contamination. 

Horizontal vs. Vertical Laminar Flow Hoods

Flow hoods come in two configurations: horizontal and vertical. Both designs provide an effective sweeping action through the work zone and meet ISO Class 5 cleanliness standards. Your application and needs will help determine which is better for your facility.

Horizontal Laminar Flow Hoods

As their name indicates, horizontal laminar flow hoods direct air horizontally. Air is pushed through a HEPA or ULPA filter positioned on the back wall and moves forward across the work surface until it exits the enclosure.

By sweeping the air across the work surface and towards the operator, horizontal laminar flow hoods provide the highest protection from contaminating particles. No turbulence is caused by vertical air striking a perpendicular surface or the hands of the operator since they’re always further downstream than the materials they are working on.

However, the hood’s size, the filter’s positioning, and the airflow’s direction can also result in some negative consequences. Below you’ll find a helpful list of pros and cons for these types of hoods:


  • Low turbulence on the work surface due to air flowing parallel to the work surface
  • Easy to position products and materials close to the filter on the work surface
  • Little contamination from hands or gloves due to the operator being downstream from products and materials


  • Requires hood repositioning to gain rear access for filter changes and servicing
  • Objects can obstruct the flow and contaminate anything downstream
  • Operators could suffer from fume or powder contaminants blowing at them if they don’t use the sash correctly

Vertical Laminar Flow Hoods

In contrast, vertical laminar flow hoods take air from above the unit, push it through the HEPA or ULPA filter, and then direct it down onto the work surface, where it eventually disperses and exits the enclosure out of a front access area. They resemble the model of a laminar flow cleanroom with fan filter units on the ceiling, just on a much smaller scale.

Vertical laminar flow hoods are popular because of their size, layout, and operator safety. Since the filter is at the top of the unit rather than behind, these flow hoods require less floor space but can be taller to fit larger products and materials. Also, since the laminar air isn’t blowing toward the operator, they are less likely to suffer any contaminants.

Vertical laminar flow hoods are an excellent choice for many applications, including handling sterile, non-hazardous drug compounding in research labs, pharmacies, and microbiology. Here’s a quick overview of their pros and cons:


  • Require less floor space
  • Increased operator safety
  • Easy access to filter changes and servicing
  • Less cross-contamination of items on the work surface due to no parallel airflow
  • A taller system that can accommodate tall and large products and materials


  • May require overhead clearance for changing and servicing the filter
  • Increased work surface turbulence due to vertical air hitting a perpendicular surface
  • Products and materials could obstruct airflow when stacked

Which Laminar Flow Hood Is Right for Your Application?

Both horizontal and vertical laminar flow hoods can be utilized for many applications involving sensitive products and materials, including (but not limited to):

  • Injectable drugs
  • IV solutions
  • Tissue culture
  • Optics
  • Microelectronics

While both types of flow hoods are optimal for reducing contamination in a workspace, a few applications lend themselves more toward one or the other. Usually, the most important factors to consider include process location, clearance requirements, size of materials, work surface design, and operator safety.

That said, horizontal laminar flow hoods generally work best for applications that require minimal turbulence on the work surface and the highest level of object contamination control. If your application’s process is performed above the work surface, a vertical airflow configuration may be ideal; particles inside a vertical unit settle at the bottom of the work surface before exiting the enclosure. Vertical hoods are also a popular choice for any applications involving materials that could be especially large or dangerous to the operator.

Contact the Cleanroom Experts at Angstrom Technology

If your cleanroom requires laminar flow hoods, Angstrom Technology can design a cleanroom that will seamlessly meet your classification and industry requirements. Our experienced design engineers are ready to collaborate with you to create a tailored solution that ensures optimal performance and adherence to industry standards. Contact us today to initiate the conversation and enhance the efficiency of your cleanroom environment.


Do You Know the Difference Between Negative Pressure vs. Positive Pressure Cleanrooms?

Do You Know the Difference Between Negative Pressure vs. Positive Pressure Cleanrooms?

In today’s fast-paced world of technology, pressurized cleanrooms are being utilized in more and more industries and applications. Two main types of cleanrooms are negative pressure rooms and positive pressure rooms. 

The level of pressure determines the way air naturally moves in a space. High and low, or positive and negative, pressure can be used as tools in cleanroom environments to help cleanrooms reach their required classifications.

Negative Pressure vs. Positive Pressure Cleanrooms

Let’s dive deeper, learn the difference between negative pressure vs. positive pressure cleanrooms, and discover how they work. 

How Does Air Pressure in Cleanrooms Work?

Air naturally flows from areas of high pressure to areas of low pressure. Examples of this are found around us every day. For example, wind and weather are formed from the uneven heating of the earth’s surface, which generates pockets of high and low pressure air. 

Have you ever witnessed the sudden closing of a door as air is sucked out of a room even though there’s no breeze? This experience is high pressure air moving to a low pressure area to achieve stasis. 

Another example of this process is when air escapes from a balloon. The air travels from a high pressure environment to the relatively low pressure of the surrounding air. 

What happens in all of these situations is that when air is moving in one direction, it’s not moving in the opposite direction. When air is moving out of the balloon, air isn’t also moving into the balloon, as long as the air inside the balloon is more pressurized. 

This concept can be applied to cleanrooms to stop airflow into a cleanroom or out of it, limiting particle transfer via the air and maintaining a cleaner environment.

To put this as simply as possible:

Higher pressure air within a cleanroom (compared to the air outside the room) blocks contaminants from entering the cleanroom, as air naturally wants to flow out. Conversely, lower pressure air within a cleanroom can trap contaminants and prevent them from leaving a cleanroom, as the natural flow of air wants to move in. 

Using Positive and Negative Pressure in Cleanroom Design

Using pressure in cleanrooms, either high pressure (positive pressure) or low pressure (negative pressure), can benefit many cleanroom applications, but how do you implement it in the cleanroom design?

Cleanroom pressure is achieved by controlling how much air is put into the cleanroom and how much is withdrawn. 

In a positive pressure cleanroom, filtered air is consistently pumped into the room through the HEPA filtration and cleanroom HVAC system. If a door or window were opened in the cleanroom, air would rush out into the outside environment. This positive pressure ensures that the products and processes within the cleanroom are protected in the event of a breach or leak. Because the cleanroom has positive pressure, the air is forced out of the cleanroom, preventing contaminated or unfiltered air from seeping in. 

To achieve negative air pressure, external exhausts pull air from the cleanroom at a faster rate than air is introduced over a span of time. The resulting negative pressure means the air will want to flow into the cleanroom to fill the low pressure area, effectively stopping contaminants from going against that natural movement to escape the cleanroom.

To maintain positive or negative pressure in cleanrooms, adjacent spaces must be maintained at a lower or higher pressure than that of the cleanroom. If you implement a pressurization system into your cleanroom design, a pressure monitoring system is vital to ensure balance and consistency. The monitoring system will check and maintain consistent pressure, which can be adjusted manually or automatically.


High pressure, or positive pressure rooms are beneficial in applications where the slightest particle interference could disrupt processes within the cleanroom. 

Semiconductor cleanrooms, microprocessor cleanrooms, and aerospace and defense cleanrooms are examples of industries that benefit from positive pressure cleanrooms, as they are highly averse to contaminating particles. Medical cleanrooms also use positive pressure to protect sensitive patients and maintain a controlled space.

Even when the stakes aren’t as high, using slightly positive pressure in cleanrooms can help reach cleanroom classifications and maintain an overall cleaner environment.


Low pressure cleanrooms, or negative pressure rooms, are ideal for applications that need to isolate substances, particles, or fumes inside the cleanroom environment to protect the space outside. They are widely used in medical cleanrooms for research, testing, and the development of treatments using sensitive substances. 

Pharmaceutical applications also use negative pressure in cleanrooms as part of a segmented layout. One room is kept at a lower pressure, while the anteroom immediately outside is maintained at a slightly higher pressure. This allows employees to transition into the negative pressure room with minimized disruption.

Need Help Choosing the Right Cleanroom Pressure? Angstrom Technology Can Help

Using the natural air movement due to pressure, we can build safer, more effective cleanrooms. Positive and negative pressure cleanrooms can protect against entering contaminants (in positive pressure cleanrooms) or contaminant leakage (in negative pressure cleanrooms). 

Which cleanroom pressure best suits your needs? At Angstrom Technology, we’re here to guide you. Our dedicated cleanroom experts are ready to precisely tailor airflow patterns and containment solutions for your unique application. Get in touch with us today for expert assistance in creating the ideal cleanroom environment for your specific requirements.