Cleanroom Terminology: Air Change Rates

Cleanroom Terminology: Air Change Rates

Air Changes per Hour are important factors in determining the design and evaluating the performance of a cleanroom. The air changes per hour, airflow pattern, and exchange efficiency all have significant implications on cleanroom performance and cost, which in turn determines the return on investment for a cleanroom.

What are air changes per hour, and how are they accounted for in cleanroom design? We’ll break down the answers to these questions and more.

What are Air Changes Per Hour?

As defined by ISO 146144-4 standards, air changes per hour refers to the number of times per hour the air in a cleanroom is replaced with clean, filtered, and treated air. It’s calculated by dividing the volume of air sent into the cleanroom as a unit of time by the total volume of the cleanroom. 

Air Changes Per Hour or Air Change Velocity

Cleanrooms, by definition, require air changes in order to meet air quality requirements for particle count and more. As the environment gets more clean with lower ISO classes, more and more air changes are needed to reach stringent classification standards

ISO standards express air changes per hour differently for cleanrooms with unidirectional and non-unidirectional airflow. 

Non-Unidirectional Airflow = Air Changes Per Hour

Non-unidirectional, or mixed flow, refers to the airflow pattern in a cleanroom. Typically, cleanrooms that fall within ISO Classes 5 and above use this type of airflow. It is sufficient for removing the designated number and size of particles at a regular rate per their classification standard. 

For cleanrooms that comply with ISO Classes 4-9, hourly air changes per hour are sufficient to express how many times the air in the cleanroom is completely refreshed. Applications like pharmaceutical, packaging and manufacturing, biosciences and health typically fall in this classification range and comply with air changes per hour as described. 

Unidirectional Airflow = Airflow Velocity

As cleanroom classifications become more stringent, the air changes per hour must increase to remove particles and keep the air cleaner. Cleanrooms with unidirectional airflow, typically Class 5 and below, have the strictest cleanroom classifications. To maintain air quality, the air changes per hour is so rapid it is expressed instead as airflow velocity, either in meters per second or feet per minute. 

These cleanroom environments must remain extremely clean, so the constant flow of contaminant-free air, either vertically or horizontally, is vital to keep particles from settling on surfaces and maintain classification standards. 

Cleanroom applications such as microelectronics, sensor manufacturing, and other sensitive processes must be performed in such environments with strict air quality control and consistent removal of contamination.

Air Changes Per Hour and Cleanroom Classifications

air changes per hour are an essential component of cleanroom classification standards. They make it possible to reach the particle count and size restrictions each class sets. Let’s take a look how air changes per hour and classification are related.

ISO 14644-1 Cleanroom Standards


Maximum Allowed Particles (per m3)

Air Changes Per Hour

Airflow Velocity (ft/min)

Ceiling Coverage

≥0.2 µm

≥0.3 µm

≥0.5 µm

≥1 µm

≥5 µm


















































































As you can see from the chart above, classes are organized by three major factors: particle size and count, air changes per hour or airflow velocity, and percentage of ceiling coverage. Once the air changes per hour rises above 200, it is better expressed as airflow velocity in feet per minute. 

What’s My Air Changes Per Hour?

The best air changes per hour for your cleanroom is the one that allows you to reach the required cleanliness required by your cleanroom classification. The level of activity and actions that introduce contaminants in your specific cleanroom may affect the amount of particles generated, and thus the air changes per hour required to remove them.

Your cleanroom’s air changes per hour describes conditions when the room is in operation, but you may lower the air changes per hour when the cleanroom is not in use to save energy and operation costs.  

Designing Cleanrooms to Meet Air Changes Per Hour

Your cleanroom is designed to meet your cleanroom classification. All the systems that support air quality and cleanliness work together to achieve consistency.

To design a cleanroom that meets your classification with adequate air changes per hour, the cleanroom must contain enough fan filter units and a uniform airflow pattern. A greater percentage ceiling coverage of fan filter units is required to reach necessary air changes. 

Although the percentage of ceiling coverage for fan filter units isn’t a metric directly referenced by ISO standards, it helps estimate construction costs. What’s most important is that the cleanroom has the systems it needs to thoroughly and consistently change the air to reach its cleanliness requirements. 

Upgrading Cleanroom Classifications and Air Changes Per Hour

If you need to upgrade your cleanroom to meet stricter classification standards or adapt your facility to handle a more sensitive project, an important step is to increase or adjust the filtration and air changes per hour to remove more particles of a smaller size from the air. 

When moving from ISO Class 7 to ISO Class 6, for example, you’ll need to increase your air changes from 60-90 ACH to 150-240 ACH to filter all but 35,200 particles at 0.5 microns per cubic meter. Consider that, to support this shift, you may need to upgrade your HVAC system.

Meet Your Classification With Cleanroom Professionals

Think you need to update your cleanroom’s air changes per hour? The cleanroom design experts at Angstrom Technology can help! We can evaluate your space and systems to ensure they’re working effectively, and help you upgrade them to change air more efficiently. To learn more, give us a call or reach out online.

Medical Cleanroom Design Tips: Cleanroom Ceilings and Fan Filter Units

Medical Cleanroom Design Tips: Cleanroom Ceilings and Fan Filter Units

Cleanroom walls, floors, doors, and other components get a lot of attention, but one of the most crucial elements of cleanroom construction is the ceiling. Cleanroom ceilings support many of the essential functions of the space, from housing fan filter units to supporting lighting and other electrical components, fire suppression systems, and more.

This is one area of medical cleanroom design that should not be overlooked. Let’s explore what your cleanroom ceiling can do — particularly when it comes to filtration and fan filter units.

Medical Cleanroom Design: Cleanroom Ceilings

Cleanroom ceilings can take many forms, depending on the requirements of each application, but the most common construction is a grid ceiling.

The grid ceiling of a medical cleanroom must support the frame and ceiling panels, lighting, and heavy fan filter units. The grid frame and all of its contents is supported by sturdy beams attached to your building structure.

With the ceiling panels installed, there should still be enough space between the ceiling and the roof for electrical and control boxes, air inlets, and fan filter unit housings. Walkable cleanroom ceilings must have enough space for a technician to maneuver above the room safely, to perform maintenance without disturbing the controlled environment inside.

Considerations for Cleanroom Ceiling Design

Cleanroom ceilings any any components, such as filters, filter housing, frames, and other penetrations for utilities, sprinklers, or lighting, must be completely sealed to prevent any contaminants from finding their way into the cleanroom. When designing the cleanroom ceiling, no wires, pipes or other obstructions should block or impair the airflow pattern from the fan filter units. 

Medical Cleanroom Ceilings and Fan Filter Units

Fan filter units are the most important part of a cleanroom ceiling. They direct clean, filtered air into your cleanroom and help maintain your classification standard. They also take up the most space, so much of cleanroom design is fitting the rest of the cleanroom — lighting, electrical, and more — around these essential components. 

What Are Fan Filter Units?

Fan filter units protect and facilitate the filtering power of the cleanroom. Combined with proper cleaning, and an expertly designed airflow pattern, fan filter units are responsible for achieving and maintaining your cleanroom classification requirements for allowed particles.

Fan filter units house your hardworking HEPA filters and upstream pre filters in an epoxy, acrylic or polystyrene-coated aluminum frame. They’re attached to the ceiling grid and fixed flush with ceiling panels to direct airflow into the room without creating turbulence.

Types of Fan Filter Units

There are different types of fan filter units, depending on the size, airflow rate, and filter media that works best for your application’s needs. A few of the common options for medical cleanrooms include:

  • Roomside Replaceable fan filter units, which feature housing that is accessible from within the cleanroom. Pharmaceutical cleanrooms require frequent testing and replacement of filters, so room-side-replacement is an advantage. These units have a gel-seal gasket that creates a seamless connection between the filter and the housing.
  • Non-roomside replaceable fan filter units, or NCR fan filter units, which are accessed from overhead the cleanroom. The advantage of NCR units is that they only require filter replacement every 3-5 years, except in certain cases where the cleanroom application generates excessive particulate matter.
  • Reverse airflow fan filter units, which are more common in medical cleanrooms working with hazardous substances, toxic fumes or contagious pathogens. A reverse airflow fan filter can be used to establish negative pressure and isolate contaminants inside the cleanroom.

All cleanrooms require air filtration using HEPA filters. Generally, the more stringent your cleanroom classification, the more fan filter units you’ll need mounted on your cleanroom ceiling. 

As you install more fan filter units, you’ll need to get creative with how other systems are installed on your ceiling. Fortunately, there are creative workarounds, like grid lighting, that leave plenty of room for your cleanroom filtration system.

How Many Fan Filter Units Does My Cleanroom Need?

The number of fan filter units your cleanroom requires depends primarily on your classification, but also your cleanroom layout and the volume of your space.

Your cleanroom classification will dictate the minimum air change rate and particle count requirements for your application. Cleanrooms with less stringent requirements may only require 5-15% ceiling coverage to be dedicated to filtration, while those with fewer particles allowed may require 60-100%.

You can determine the number of fan filters required by comparing the capacity of each filter fan unit with the total volume of your space.

Need some help building the perfect high-performance ceiling to reach your cleanroom classification? Angstrom Technology would love to help your medical cleanroom achieve optimal airflow, filtration, and pressurization for your application. Give us a call to get started!

Conductive vs. Anti-Static Cleanrooms: Which is Better for the Aerospace Industry?

Conductive vs. Anti-Static Cleanrooms: Which is Better for the Aerospace Industry?

Materials, equipment, and processes within aerospace cleanrooms make them more likely to generate static charges, as well as more vulnerable to the effects of static electricity. Metallic materials used to produce aircraft and spacecraft and their components can carry electrostatic charges, but even cleanroom-grade materials that aren’t metallic, such as vinyl or plastic, can generate static electricity.

Managing Static Electricity in Aerospace Cleanrooms

Managing electricity generated by static or other causes is essential for aerospace and defense cleanrooms that work with electronics, sensitive hardware, or unstable compounds. Particularly in aerospace cleanrooms, precautions must be taken to: 

  • Prevent the buildup of charges could attract contaminants to adhere to the surface of hardware, causing them to fail.
  • Limit the chance of sparks which could ignite flammable materials and hazardous substances within the cleanroom.
  • Protect personnel from electrostatic charges which could cause injury or spontaneous muscle movement which could cause damage to themselves, the cleanroom and its products, or others. 

Static control measures can prevent or reduce the severity of hazards that result from static electricity as well as protect sensitive equipment. Using the right materials to manage static charges and allow excess electrons to flow safely to ground can make your aerospace cleanroom safer for your work and your workers.

Dissipative, Insulative, and Conductive vs. Anti-Static Cleanrooms

When it comes to managing static electricity in aerospace cleanrooms, there are a few key terms to know: conductive, anti-static, static dissipative, and insulative. All of these materials interact with static electricity in different ways, which makes them more suitable for some applications over others. Let’s break down each of these static control materials.

Dissipative Cleanroom Materials

Dissipative cleanroom materials are more resistant to the flow of electrons. They allow static charges to travel to ground in a more controlled manner than conductive materials.

Insulative Cleanroom Materials

Insulative cleanroom materials are very resistant to flowing electrons. Not only are these materials difficult to ground, but they can also retain static charges.

Conductive Cleanroom Materials

Conductive cleanroom materials allow electrons to flow easily. They’re used to direct static charges to ground and away from sensitive products, hardware, or substances. The conductive materials themselves must only generate very low charges.

Anti-Static Cleanroom Materials

Anti-static cleanroom materials prevent the buildup of static electricity altogether. Anti-static materials are typically treated with a coating to reduce or remove static charges.

Conductive vs. Antistatic: Which is Better for Aerospace Cleanrooms?

The best materials to use in aerospace cleanrooms for static control are conductive or static dissipative materials like stainless steel, carbon, or hard plastics filled with metal fibers. A grounded copper bar placed around the perimeter of the cleanroom, three feet above the floor, is a common solution.

All materials used to control static in aerospace cleanrooms must be low-outgassing and non-particle shedding. They must not transfer any films or particles that could contaminate sensitive hardware or equipment, which means materials treated with anti-static coatings are also likely unsuitable.

Get Professional Help Managing Static In Your Cleanroom

Not sure if conductive or antistatic is better for your cleanroom? Angstrom Technology’s cleanroom design experts can help you determine the best materials and systems to use for your application. Simply give us a call to get started!

5 Advantages of Modular Cleanrooms for the Plastics Industry

5 Advantages of Modular Cleanrooms for the Plastics Industry

Modular cleanrooms are popular in many industries because of their versatility, durability, and cost effectiveness. They can offer several advantages for the plastics industry to help companies streamline their operations and meet their classification requirements effortlessly. 

Let’s take a look at 5 specific advantages plastics industry cleanrooms can enjoy by going modular.

#1 Modular Cleanrooms are Convenient and Easy to Assemble

Modular cleanrooms are designed to streamline the cleanroom design and construction process. Fabricated off site to your exact specifications, modular panels come pre-wired and insulated, with all the special features you need to make your project a success. They can be assembled according to a detailed set of instructions and integrated with your cleanroom systems — providing you with a fully functional cleanroom with minimum disruption to your facility’s operations.

In the plastics industry, efficiency is key. With a short turnaround time on many projects, having a powerful, convenient cleanroom option that can be designed, built, and installed quickly can make all the difference. Modular cleanrooms provide all the environmental control and stability you need, without the lengthy and expensive process of traditional construction.

#2 Modular Cleanrooms Can be Reconfigured or Expanded

Another great advantage of going modular, is that this cleanroom type can easily be reconfigured, expanded, condensed, or even moved if your project needs change. Modular panels allow for the ultimate flexibility of cleanroom construction — without sacrificing quality. By adding or taking away panels, you can reshape your space to fit in your existing structure, around mounted equipment, and utilize your building’s systems.

Modular cleanrooms used for application in the plastics industry must be able to adapt to changing project demands or goals. A cleanroom that can be easily modified to meet new requirements or be reconfigured to accommodate new equipment, personnel, or products, not only makes it easier to get started on whatever’s next, but it can also save your company money. 

Instead of building new cleanrooms to conform to the classification standards, industry requirements, and cleanroom systems of each new project — one modular cleanroom can do it all.

#3 Modular Cleanrooms Can Meet Any Classification Standard

Modular cleanrooms can adapt to any cleanroom classification or industry standard for cleanliness and environmental control. There are three main types which can meet the needs of your classification and application:

  • HardWall Cleanrooms: capable of reaching any ISO classification — even the most stringent Class 1
  • SoftWall Cleanrooms: lightweight and flexible cleanroom construction ideal for ISO Classes 4-8
  • RigidWall Cleanrooms: crystal-clear modular panels best suited for ISO Classes 5-8

In the plastics industry, cleanrooms must be able to control temperatures and environmental conditions to maintain large machinery that generates significant heat. Plastics cleanrooms must be able to ensure sterility during the manufacturing and packaging of plastics products. 

Especially for the development of plastics for critical uses, like medical devices, extreme care and cleanliness is essential for consumer safety. Modular cleanrooms are able to provide the sterile environment these applications need to be successful.

#4 Modular Cleanrooms are Built to Withstand Anything

Plastics industry cleanrooms have multiple processes in motion at all times, from traffic of personnel, carts, and cranes, to the operation of large equipment like plastic injection molding machines, which can range in size from 50 to 1,000 tons. 

Plastics cleanrooms require consistent cleaning to maintain quality standards and ensure the facility performs at optimal levels. A durable cleanroom is essential to handle day-to-day operations and proper sterilization.

Extremely durable modular panels are made with non outgassing and non particle shedding materials, and designed to withstand anything. They’re fire and impact resistant and can handle thorough, regular cleaning protocols without corroding or losing integrity. ESD-safe materials are also available for sensitive applications.

#5 Modular Cleanrooms are Customizable to Your Application

Modular cleanrooms are designed and built off site, but they can still be constructed with full range of customizations. Depending on what you need your cleanroom to do, your cleanroom will support your custom layout, airflow pattern, industry-specific equipment, and cleanroom trades like your HVAC, lighting, and filtration systems. 

You can even have your modular cleanroom designed to integrate with systems in your existing structure, so it will fit in any sized space, utilize light from existing windows, connect to your air handling system, and more.

Applications in the plastics industry can use modular cleanrooms to meet requirements set by the ISO and their industry, and set their project up for success by incorporating all the tools and features they’ll need in their modular cleanroom design.

Ready to get started on a modular cleanroom? Give Angstrom Technology a call! We design, build, and install modular cleanrooms to meet any classification requirements. Our prefabricated panels come with detailed instructions, ready to set up right away. Of course, if you’d rather skip the work, have our cleanroom experts install it for you!

3 Cleanroom Applications that Use Seamless Cleanroom Solutions

3 Cleanroom Applications that Use Seamless Cleanroom Solutions

There are endless types of cleanrooms out there, each with their own cleanroom design, layout, features, ISO classification, and more. With all of the available customizations, each cleanroom application can have a modular cleanroom that is completely tailored to their project needs and goals.

Seamless cleanrooms are a type of modular construction that can be fully customized to any application and built within a facility’s existing structure. They have unique strengths and capabilities that make them ideal for many common cleanroom applications. Let’s take a look at a few industries that use seamless cleanroom solutions to conduct their work.

3 Cleanroom Applications that Use Seamless Cleanroom Solutions

Three common industries that use seamless cleanrooms to provide the ideal, controlled environment for their work are semiconductor , pharmaceutical , and medical device. Let’s take a look at a few of the benefits this cleanroom type offers these diverse applications and why seamless is the perfect cleanroom solution.

Seamless Semiconductor Cleanrooms

Semiconductor cleanrooms require a high level of control during the manufacturing and handling of semiconductors, due to the sensitive nature of the material. They must be able to limit contamination by air and surface particles to an extreme degree, which is why they must comply with ISO 14644-1 Class 5 or lower classification standards. 

Seamless cleanrooms are the best fit for semiconductor applications because their construction prohibits the settling of particles in any crevice where they could build up and contaminate the work in the room. The durable wall panels of a seamless cleanroom are sealed with a resistant shell that won’t corrode or shed particles during cleaning or in case of impact. 

Semiconductor production facilities rely on seamless cleanroom solutions to protect delicate work with fine electronics, silicon wafers, sensors and more.

Seamless Pharmaceutical Cleanrooms

In a pharmaceutical cleanroom, control is key. Even the slightest contamination or stray particle could skew test results, corrupt pharmaceutical products, or put employees at risk. Cleanrooms used in pharmaceutical applications require strict maintenance of air quality protocols. The materials of the cleanroom must be able to withstand thorough and robust cleaning chemicals and procedures without shedding particles or sacrificing environmental control.

Pharmaceutical cleanrooms often use seamless modular construction for the processing and development of beneficial medicines and products. For the critical applications of pharmaceutical research with sensitive substances, a seamless cleanroom solution is able to reach an extreme level of environmental control — protecting both the work and the workers.

Seamless Medical Device Cleanrooms

Medical device cleanrooms require environmental uniformity in order to manufacture, test, and package sensitive devices and medical technology. If particles contaminate medical devices or their packaging during any part of the process, the device could fail and put lives at risk. To avoid this, a seamless cleanroom can be used.

Seamless cleanrooms provide medical device applications with the ultimate control over air and surface particles. With no seams for particles to settle and collect, the cleanroom HVAC and filtration system can be fully effective at removing particles according to stringent ISO classifications. 

This cleanroom application is also susceptible to static electricity, so a seamless antistatic floor material is often used with a seamless cleanroom solution to prevent charges or sparks from corrupting devices or harming employees.

Seamless Cleanroom Design and Construction

Seamless cleanroom solutions are fully customizable and can be built to any cleanroom classification, which makes them an ideal choice for a wide range of applications. 

Your seamless cleanroom includes integration with your cleanroom systems and trades, such as cleanroom HVAC, filtration, lighting, and more. It can be installed in your existing structure and outfitted with all the special features you need to make your project a success.

If you think a seamless cleanroom would be perfect for your application, give the experts at Angstrom Technology a call. We specialize in seamless cleanroom solutions with modular construction, and we consistently deliver industry-leading cleanrooms across the country. Yours could be next.