Importance of Cleanroom Airflow Uniformity

Importance of Cleanroom Airflow Uniformity

Cleanrooms are designed to maintain strict control over environmental factors, but they’re only effective if they have an expertly designed airflow pattern to help them reach the desired cleanliness level and ISO classification standard. ISO document 14644-4 describes airflow patterns to be used in cleanrooms at the different classification levels in order to maintain strict airborne particle counts and cleanliness. 

Cleanroom airflow must allow the air within the cleanroom to be completely changed to remove particles and potential contaminants before they can settle. In order to do this properly, the airflow pattern must be uniform — ensuring every part of the space can be reached with clean, filtered air.

To break down the importance of cleanroom airflow uniformity, we need to start by looking at the three main types of airflow in cleanrooms.

 

3 Types of Cleanroom Airflow Patterns

 

Cleanroom airflow can be unidirectional, non-unidirectional, or mixed — a combination of both. The best cleanroom airflow type will depend on the cleanroom classification. Generally, cleanrooms of an ISO Class 6 or greater can use a mixed or non-unidirectional airflow pattern, while ISO Class 5 (or cleaner) cleanrooms rely on unidirectional airflow.

 

#1 Unidirectional Cleanroom Airflow

 

This type of cleanroom air moves in one direction across the room, either horizontally or vertically from fan filter units to the exhaust system that removes “dirty” air. Unidirectional flow requires as little disturbance as possible to maintain a uniform pattern.

 

#2 Non-Unidirectional Cleanroom Airflow

 

In a non-unidirectional airflow pattern, air enters the cleanroom from filter units located in multiple locations,  either spaced throughout the room or grouped together. There are still planned entrance and exit points for air to flow along more than one path.

Although air quality is less critical compared to unidirectional airflow cleanrooms, special attention should be paid to make sure air is changed thoroughly, minimizing the potential for “dead zones” within the cleanroom. 

Dead zones are areas where air is turbulent or not being changed and may result in deposited particles or a buildup of contaminants.

 

#3 Mixed Cleanroom Airflow

 

Mixed airflow combines both unidirectional and non-unidirectional airflow. Unidirectional airflow may be used in specific areas to boost protection around working areas or more sensitive materials, while non-unidirectional airflow still circulates clean, filtered air throughout the rest of the room.

mixed cleanroom airflow

 

Why Cleanroom Airflow Uniformity Matters

 

Whether a cleanroom airflow is unidirectional, non-unidirectional, or mixed, having a uniform cleanroom airflow pattern matters. Cleanrooms are meant to be controlled environments where all systems should work to prevent areas where buildup of contaminants can occur — via dead zones or turbulence. 

 

What is Turbulent Air?

 

Turbulent air, or chaotic air, in a cleanroom is a serious threat to cleanliness. Turbulent air occurs when the airflow pattern is not uniform.

Think of a current moving through water. If the flow was uniform, all of the water would move steadily at the same speed. Obstructions or varying speeds, like rocks or rapids, impede the uniformity of the flowing water. Similarly, when you sweep your hand through water and see eddies and whirlpools form to the side of the current, that’s turbulence. 

Eddies in water may be harmless, but turbulence in cleanroom airflow can cause the uncontrolled movement of contaminating particles — or dead zones where no air is moving at all, where contaminants can build up and threaten sensitive processes in the cleanroom.

 

What Causes Turbulent Air in Cleanrooms? 

 

Turbulence in cleanroom airflow can be caused by non-uniform speeds of air entering the room or obstructions in the path of incoming or outgoing air. Airflow uniformity is about preventing unnecessary turbulent air so the cleanroom can perform at peak efficiency.

 

Minimizing Turbulence in Cleanrooms

 

You can minimize turbulence by designing the cleanroom airflow pattern to work with your layout, equipment, furniture, and personnel. The cleanroom should be removing air at the same or similar speed as it enters. This gives air a clear path to flow to prevent turbulence and dead zones.

Obstructions can also cause turbulent air, so make sure that no large furniture or equipment is blocking fan filter units or exhaust. Adjust equipment with aerodynamic attachments or design features to facilitate airflow, use perforated cleanroom tables to allow air to pass through uninhibited, or modify behavior of personnel to not block or impede airflow within critical zones.

Minimizing Turbulence in Cleanrooms

 

Cleanroom Airflow and Pressurization

 

Another way to minimize contamination using a uniform airflow pattern to establish positive or negative air pressure. Cleanroom pressurization creates a natural barrier to protect or isolate cleaner or less clean zones, respectively. Using negative and positive pressure can be especially useful for sensitive applications such as the manufacturing of healthcare products, medical research, microelectronics, and more.

 

Custom Cleanroom Airflow Design

 

Cleanroom airflow patterns should be designed to work with each unique cleanroom layout and all the furniture, systems, and personnel in the cleanroom for optimal cleanliness during operation. 

A cleanroom engineer uses computational fluid dynamics to map out the cleanroom and place fan filter units and outlets appropriately to meet your classification requirements. This system allows the designer to visualize the pattern of air and make adjustments for cleanroom systems, equipment, and personnel in order to achieve uniformity. It also allows you to anticipate your energy requirements and make your facility as efficient as possible. 

As your ISO cleanroom classification gets lower, having an expertly designed airflow pattern becomes more and more crucial. Work with an expert to make sure your cleanroom airflow is as uniform as possible for your application.

 

Trust the Angstrom Technology Cleanroom Airflow Design Experts

Designing your cleanroom and need a little help establishing an efficient, uniform airflow pattern? Call the experts at Angstrom Technology. From cleanroom airflow design to HVAC and filtration maintenance, we can help you make the best choices for your budget and your classification. 

cleanroom-classification-quiz-cta
Understanding Air Pressure in Cleanrooms

Understanding Air Pressure in Cleanrooms

Pressurized cleanrooms are used in a range of industries and applications. Varying levels of pressure determines the way air naturally moves in a space. High and low pressure, or positive and negative pressure, can be used as a tool in cleanroom environments to help cleanrooms reach their cleanroom classifications and protect their products and people. Let’s explore air pressure in cleanrooms to discover how it works.

 

 

How Does Air Pressure in Cleanrooms Work?

 

 

It’s a well-known natural process for air to flow from high to low pressure. Examples of this are found around us every day. Wind and weather are formed from the uneven heating of the earth’s surface, which generates pockets of high and low pressure air. If you’ve ever witnessed the sudden closing of a door as air is sucked out of a room where no breeze was felt, what you experienced was the high pressure air moving to a low pressure area to achieve stasis. Air escaping from a balloon is traveling 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 the opposite direction. When air is moving out of the balloon, there isn’t also air moving into the balloon, as long as the air inside the balloon is more pressurized. This concept can be applied to cleanrooms, to stop the flow of air into a cleanroom, or out of it, limiting particle transfer via the air and maintaining a cleaner environment.

To state this more plainly, higher pressure air within a cleanroom (compared to the air outside the room) blocks against contaminants 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 pressure in cleanrooms, either higher pressure (positive pressure), or lower pressure (negative pressure) can be extremely useful in many cleanroom applications — but how do you implement it in the cleanroom design?

 

 

Using Pressure in Cleanroom Design

 

 

Positive and negative pressure in cleanrooms is achieved by controlling how much air is put into the cleanroom, and how much is withdrawn. 

In a positive pressure cleanroom, clean, filtered air is consistently pumped into the room through the HEPA filtration and cleanroom HVAC system. In the event that a door or window was opened in the cleanroom, air would rush out into the outside environment. 

This positive pressure ensures that in the event of a breach or leak in the cleanroom, the products and processes within the cleanroom are protected. 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 air will want to flow into the cleanroom to fill the low pressure area, effectively stopping contaminants from going against that natural movement in order to escape the cleanroom.

To maintain either positive or negative pressure in cleanrooms, adjacent spaces must be maintained at a lower or higher pressure than that of the cleanroom, respectively.

If you implement a pressurization system into your cleanroom design, having a pressure monitoring system is important to ensuring balance and consistency within your cleanroom. The monitoring system will check and maintain consistent pressure, which can be adjusted manually or automatically.

 

 

Positive Pressure Cleanroom Applications

 

 

High pressure, or positive pressure cleanrooms are extremely useful in applications where the slightest particle interference could disrupt processes within the cleanroom. Semiconductor cleanrooms, microprocessor cleanrooms, and aerospace and defense cleanrooms are just a few examples of industries that benefit from positive pressure cleanrooms, as they are extremely averse to contaminating particles. Many medical cleanrooms use positive pressure, to protect sensitive patients and maintain a controlled space.

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

 

 

Negative Pressure Cleanroom Applications

 

 

Low pressure cleanrooms, or negative pressure cleanrooms, are ideal for applications that need to isolate substances, particles, or fumes inside the cleanroom environment to protect the space outside of the cleanroom. They are widely used in medical cleanrooms, for medical 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 ante room immediately outside it is maintained at a slightly higher pressure. This allows employees to transition into the negative pressure room with minimized disruption.

High and low pressure, or positive and negative pressure, can both be used as tools in cleanroom environments to protect against entering contaminants (in positive pressure cleanrooms) or contaminant leakage (in negative pressure cleanrooms). Using the natural movement of air due to pressure, we can build safer, more effective cleanrooms.

Think a negative or positive pressure cleanroom is right for you? Reach out to Angstrom Technology. Our cleanroom experts can design the best air flow patterns and containment systems for your application.

Understanding Cleanroom HVAC Requirements

Understanding Cleanroom HVAC Requirements

Just as different cleanrooms have different requirements for class specifications, HVAC systems are not one-size-fits-all. Your cleanroom HVAC system might even have to be reconfigured to best suit the needs of your facility. 

If your cleanroom is the body that enables you to manufacture, test or create your products, the HVAC system is its lungs. When functioning efficiently, a cleanroom can control down to a minute detail the temperature, pressure, humidity, particles, and levels of contamination of its contents. To do this, the cleanroom must be able to change its air and filter particulates. If the cleanroom is unable to do this, it is essentially left breathless.

The process of changing air can happen from 10 to more than 600 times per hour. The less “clean” the room has to be, the less often the air will change. Conversely, the more stringent the cleanroom’s standards, the more often the air will have to be changed per hour. This is referred to as air-change rate or ACR.

 

Understanding Cleanroom HVAC Power Levels and Capabilities

HVAC systems differ in their power levels and capabilities. If your cleanroom has lower standards, it may not need a system with a high BTU (British thermal unit of heat required to raise temperature in a pound of water by one degree), and strictness in temperature regulation or relative humidity (rh) may not be necessary. Cleanrooms that require exactness in these levels and extremely fine particulate filtration, however, may need the investment of a powerful HVAC system, one that is capable of maintaining a consistent and controlled environment for employees and their work.

Different industries have different requirements, and therefore different cleanroom HVAC needs. To help break this down, we’ve divided cleanroom users into three broad categories: Manufacturing, Pharmaceutical, and Laboratory. Of course, many exceptions exist. For a more specific consultation, reach out to our cleanroom design team.

 

Manufacturing Cleanroom HVAC Requirements

 

hvac requirements

 

Cleanrooms used in manufacturing facilities are designed to meet a variety of standards, depending on the specific products they involve and the size of the particulates that need to be filtered. Most manufacturing cleanrooms meet ISO Classes 7 or 8, which translates to a maximum number of particles of .05μ or greater in the air ranging from 352,000 to 3,520,000. Since this type of facility does not typically depend on extreme control of temperature or a high ACR, they can be adequately maintained with the use of an HVAC system with an average to low BTU level. 

 

Pharmaceutical Cleanroom HVAC Requirements

 

hvac requirements cleanroom

 

Pharmaceutical cleanrooms will need much higher control over environmental variables and so will need a powerful HVAC system to help them achieve this. They will need to maintain a strict temperature range as set forth in all USP regulations in order to stabilize materials, meaning precise heating and cooling — especially if the cleanroom is located in a climate that experiences many temperature variations such as the Midwest. Pharmaceutical cleanrooms, on average, must comply with a minimum ISO 7 standard — Federal Standard 209 Class 10,000.

 

Laboratory and Medical Device Cleanroom HVAC Requirements

Laboratory work, especially the development and production of medical devices, requires an extremely controlled cleanroom environment that must comply with intensive standards. The majority of these types of cleanrooms comply with ISO 14644 standards. A powerful HVAC system with the necessary filters will restrict particulates in the environment to the acceptable level, maintaining the quality of the cleanroom’s air. In this environment, the air will need to be changed with high consistency, removing any contaminants before they interfere with the integrity of the work.

Depending on the size of the particles that need to be filtered, the importance of temperature or humidity to your products and the ACR rate needed to keep your environment clean, your system capabilities will need to reflect the type of work conducted in your facility. With the proper cleanroom HVAC system working in tandem with your perfectly equipped cleanroom, you will have complete control over your space and the products developed within it. It’s important to make sure your HVAC is able to filter and properly change the air of your cleanroom so it can breathe and function efficiently.

 

It’s possible that your current HVAC system may not be up to the task of supporting your new cleanroom. That’s where Angstrom Technology comes in. As expert cleanroom designers, we can help you determine what type of HVAC system you need, and help you make it happen, too. For help designing, installing, or servicing your cleanroom’s HVAC system, give our team of experts a call at 888-768-6900 or contact us online today.

Understanding Cleanroom HVAC Requirements

Cleanroom HVAC Systems Explained

In cleanrooms, air is crucial – how it’s filtered, how it’s heated and cooled, and how it’s circulated. Because of this, knowing how HVAC and filters work together is crucial to maintaining cleanroom air decontamination and meeting cleanroom standards. Before you install a new cleanroom, here’s what you need to know about your cleanroom’s HVAC system:

Dedicated vs. Integrated HVAC

When it comes to cleanroom HVAC systems, the first decision is whether to have a dedicated HVAC system or to incorporate your building’s existing HVAC. This depends on the necessary level of environmental control, the size of your cleanroom, and the other energy requirements of your facilities. Using an existing HVAC system can help you save money at the outset, but for very large cleanrooms or factories, a dedicated system might be more efficient and keep a reasonable load on each system so that they can run efficiently. Additionally, while you can combine a filtration system with an existing HVAC system very efficiently, for extremely stringent cleanroom standards, dedicated HVAC may be your best bet.

Filtration systems

Filtration is also an important consideration here. There are three basic types of filters used in cleanrooms: prefilters, HEPA filters, and ULPA filters. Prefilters are used with both HEPA and ULPA filters as a first step in the filtration process, removing large particles.

HEPA filters are High-Efficiency Particulate Air filters, and they filter out 99.99 percent of particles 0.3µm or larger.

ULPA filters are Ultra Low Particulate Air filters, and filter out 99.999 percent of particles larger than 0.12µm.

Purity Testing

Once your HVAC and filtration systems are in place, you must regularly test the air purity of your system. Testing should occur initially in three phases: as-built testing (when all services are connected and working), at rest (when all equipment is installed and in place), and performance qualification (occurring regularly while the cleanroom is in operation).  

Are you designing a new cleanroom or updating an existing one? Angstrom Technology has the products and expertise you need.

What’s the Difference Between Positive and Negative Air Pressure Cleanrooms?

What’s the Difference Between Positive and Negative Air Pressure Cleanrooms?

If you’re considering a cleanroom, you’re probably trying to gather as much information as possible. What type of cleanroom is right for you? What industry standards do you have to meet? Where will your cleanroom go? You get the picture. Well, one piece of information that might be useful to you is understanding the difference between positive and negative air pressure cleanrooms. As you probably already know, airflow plays a leading role in keeping your cleanroom to standard, but what you may not have known is that air pressure can have a big effect on that as well. So here’s a broken down explanation of each positive and negative air pressure.

 

Positive Air Pressure Cleanrooms

 

This means that the air pressure inside your cleanroom is greater than the pressure outside of it. This is achieved by pumping clean, filtered air into the cleanroom, generally through the ceiling.

Positive pressure is used in cleanrooms where the priority is keeping any possible germs or contaminants out of the cleanroom. In the event that there was a leak, or a door opened, clean air would be forced out of the cleanroom, rather than unfiltered air being allowed into the cleanroom. This works somewhat similarly to deflating a balloon; when you untie a balloon, or pop it, air rushes out because the air pressure in the balloon is higher than the pressure of the ambient air.

Positive pressure cleanrooms are used primarily for industries where the cleanroom functions to keep the product clean and safe from particulates, like in the microelectronic industry where even the tiniest particle can damage the integrity of the microchips being manufactured.

 

Negative Air Pressure Cleanrooms

 

In a negative air pressure cleanroom, the air pressure in the room is lower than the pressure outside of the room. Generally this is achieved by filtering air out of the room. In most situations, air enters through filters near the floor, and then is sucked out through filters in the room ceiling.

Negative air pressure is used in cleanrooms where the goal is to keep any possible contamination from escaping the cleanroom. Windows and doors have to be completely sealed, and by having a lower pressure, air outside the cleanroom is likely to flow into it, rather than out of it. Think of it like an empty cup that you set in a bucket of water. If you push the cup into the water rightside up, water flows into the cup, because it has lower pressure than the water. The negative pressure cleanroom is like the empty cup here.

Negative air pressure cleanrooms are used in industries that manufacture pharmaceutical products, do biochemical testing, and also in hospitals to quarantine seriously contagious patients. Any air that flows out of the room has to first flow out of a filter, ensuring that no contaminants can escape.

 

dwyer digital differential pressure gauge

 

If you have any more questions regarding negative and positive air pressure cleanrooms, take a look at our Dwyer Digital Differential Pressure Gauge or if you’re looking to purchase a cleanroom for your business, give the experts at Angstrom a call today! We custom design all of our cleanrooms, so that they meet your exact specifications and standards. Call us at 888-768-6900, or contact us online.

 

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