Liberty Industries is a leading provider of cleanroom and contamination control supplies for laboratories, healthcare providers, manufacturing facilities, and more. Our innovative solutions are designed to deliver the best results across a wide spectrum of industries and have been a primary contributor to cleanroom history and innovation.
The legacy of the cleanroom can be initially traced back to French chemist, Louis Pasteur, one of the originators of medical microbiology. His research throughout the mid- to late-1800s revealed the effects of microbes on organic tissue. Through his tireless study, Pasteur discovered that boiling water and air exclusion would prevent meat from decomposing, establishing his namesake process of pasteurization. From this discovery, he also posited that the exclusion of microbes could reduce or prevent the spread of disease, which led to the development of the first cleanrooms.
Based on Pasteur’s germ theory, British surgeon Joseph Lister first used antiseptics in surgery to create sterile operating rooms. In 1867, he began to use carbolic acid to clean his hands and instruments and found that this significantly reduced bacterial infection in his patients. This successful attempt to control microbial spread in a targeted environment gave rise to the concept of cleanrooms, and in the 1960s the idea truly took root.
The Forefather(s) of the Modern Cleanroom
In the 1960s, scientist Willis Whitfield worked at Sandia National Laboratories, a federally funded scientific research facility in Albuquerque, New Mexico. Whitfield developed the first forced-air filtration system to control the number of airborne particles within an enclosed space. He filed this as the first cleanroom design, called Ultra Clean Room, under U.S. Patent No. 3158457 in 1964, an accomplishment that saw him inducted into the U.S. National Inventors Hall of Fame.
Whitfield used gravity and forced air circulation to create a controlled space with extremely low levels of particulate matter. The circulation initiated at the top of the room, where incoming air was forced into the enclosure through HEPA filters in the ceiling. Particulate matter was forced to the ground and drawn out at the bottom of the room. Though the first cleanroom was only able to hold a single adult male, cleanroom technology has since evolved rapidly and now sees broad usage across a variety of large-scale operations, from medical research facilities to electronics manufacturing.
John Nappi, Sr. & the Evolution of Liberty Industries
In 1953, Liberty was founded by John Nappi, Sr. under the name Liberty Machine Company. A visionary entrepreneur and inventor, John Nappi designed and manufactured tooling and machinery for companies throughout Connecticut. With the advent of cleanrooms in the 1960s, the company was uniquely suited to provide innovative contamination control solutions for a wide range of cleanroom applications.
As cleanroom technology advanced, John Nappi continued to develop useful and practical products, including Tacky Mats®, Shoe Brush Cleaners, air showers, and laminar flow devices. In the 1960s, he updated the company’s name to Liberty Industries, Inc. to reflect its new mission and diversified specialization.
John Nappi’s son, John J. Nappi, Jr., followed in his father’s footsteps by acquiring the business in 1973. The company has continued to develop advanced cleanroom and contamination control technology for a wide range of industries, including pharmaceutical, medical, nuclear power, electronics manufacturing, aerospace, and precision manufacturing.
Over the course of many decades, Liberty has evolved from a small machine shop manned by an intrepid entrepreneur to a world-class manufacturer of state-of-the-art cleanroom technology. Our company continues to push the boundaries of the industry, acquiring the latest manufacturing technology and continuously developing new products and processes. No matter how advanced our technology has become, we hold to the values our company was founded under in 1953: honesty, integrity, commitment, and reliability.
As Liberty Industries has grown, so has the Nappi family. As a family-owned and operated company, Liberty has seen the introduction of a third generation in John J. Nappi, Jr.’s son, Giovanni J. Nappi III. Giovanni has been around the business his entire life and understands every aspect from the ground up. He initially founded Liberty Coatings in 2006, a subsidiary of Liberty Industries Inc. which provides Cerakote® finishes to industry-leading manufacturers in the sectors of firearms, automotive, and industrial coatings. Liberty Coatings operates with the philosophy that when high-quality services are offered, delivered on time, and at a competitive price, the company will exceed clients’ expectations. The coatings division has contributed to the range of diversity in the Liberty Industries customer base. Due to John J. Nappi Jr. and his son Giovanni’s direction, the company continues to grow and prosper through quality product manufacturing and innovation.
Liberty Industries for All Your Cleanroom Needs
With a firm foundation in the fundamental science of cleanroom technology, Liberty Industries has scaled the heights of cleanroom and contamination control technology. As a world-class leader in the development and manufacture of cleanroom products, we employ some of the finest minds in the industry to help our customers find the ideal cleanroom setup and supplies for any project. Contact our experts today to learn more about our cleanroom and contamination control products and services.
At Liberty Industries, we serve as a one-stop source for all cleanroom needs. For over six decades, we have supplied superior cleanroom and contamination control supplies to customers across the globe. Equipped with extensive industry experience, our team has the knowledge and skills to design and develop a standard or custom cleanroom solution suitable for any critical environment.
In the following article, we provide an overview of one of the key operating principles of cleanrooms—differential pressure. We outline what it is, how we measure it, and how it affects other conditions in a cleanroom.
Differential Pressure in Cleanrooms
Differential pressure refers to the difference in air pressure from one location to another within a system. In cleanrooms, maintaining the right amount of differential pressure—either positive or negative—is essential to preventing contamination.
In positive differential pressure cleanrooms, the internal pressure is greater than the external pressure to prevent the ingress of any contaminants through any opening—whether intended or accidental—in the cleanroom.
In negative differential pressure cleanrooms, the external pressure is greater than the internal pressure to prevent the egress of any potentially harmful compounds contained within the cleanroom.
Combined with appropriate temperature, humidity, and airflow level, proper differential pressure levels ensure both cleanroom designs work as intended. As such, it is essential to carefully measure and monitor pressure inside and outside of the cleanroom to confirm the differential remains within the acceptable range.
Industry professionals often employ visual gauges or meters to facilitate the identification of current pressure levels inside and outside of cleanrooms. The devices are designed to automatically calculate and output the difference between two pressure points in the cleanroom (typically two inlet points), eliminating the need for operators to manually monitor separate gauges and calculate the difference between the results. More advanced measuring instruments may offer additional capabilities for monitoring temperature, humidity, and other cleanroom parameters.
At Liberty Industries, we offer Magnehelic gauges for these applications. They provide accurate measurement of pressure, pressure differential, and vacuum to 2% of full scale. In addition to cleanrooms, typical use cases include automatic valves, control equipment, and gas-air ratio controls.
Cleanroom Standards
The level of cleanliness required from a cleanroom depends on the industry and industrial application. For this reason, cleanrooms are available in numerous classifications, each of which denotes a specific level attainable based on the number and size of contaminants with the given space.
The International Organization for Standardization (ISO) categorizes cleanrooms from ISO 1 to ISO 9, with ISO 1 having the fewest contaminants per square meter. In addition to the number of particulates, the size of particulates also plays a crucial role in ISO classification. Contaminants are measured in microns, from 1μm to 5μm, with different cleanrooms offering different filtration capacities for each size. For example, cleanrooms with HEPA filters remove particulates as small as 0.3μm with 99.99% efficiency rates, while cleanrooms with ultra-low particulate filters remove particulates as small as 0.12μm with an efficiency rate of 99.999%.
The effectiveness of the mechanisms that facilitate cleanroom operations—including the filters—depend on many factors remaining within tolerable levels. These factors include pressure, temperature, humidity, and airflow, all of which can help or hinder the attainment and maintenance of proper cleanliness levels.
Quality Cleanroom Solutions From Liberty Industries
Cleanrooms play a critical role in many sensitive industries and industrial applications. For these instruments to work correctly, maintaining proper differential pressures (among other factors) is essential. To learn more about cleanrooms and the role differential pressure plays in their operation, contact us today. For assistance selecting and sourcing a cleanroom solution for your facility, request a quote.
Since 1953, Liberty Industries has been creating high quality cleanrooms, cleanroom filtration systems, and contamination control supplies. We have more than 65 years of experience designing and building customized cleanrooms for use in a diverse range of industries by customers around the world.
The filtration system is a critical component of any cleanroom. Well-designed cleanrooms require air filters that control air flow, remove particles from the room, and keep external pollutants out to prevent contamination of manufacturing processes, critical research or other projects.
The Facts About Cleanroom Filtration
Understanding the basics about cleanroom filtration can help to avoid contamination and ensure that the cleanroom is functioning at an optimal level. Here are five important facts:
1. There are three types of air filters.
Pre-filters. These filters pre-remove larger particles from the air before the it reaches more comprehensive HEPA or ULPA filters, extending the lifespan of the more expensive filters.
HEPA filters. High-Efficiency Particulate Air (HEPA) filters are the most commonly used filter, with capabilities to filter particles of 0.3µm or larger. Depending on the application, HEPA filters can last more than seven years before replacement is required in many applications. Based on specific cleanroom protocol, filters may have to be changed more often.
ULPA filters. Ultra Low Particulate Air (ULPA) filters are similar to HEPA filters, though they are capable of removing 99.999% of contaminants larger than 0.12µm. This capability to remove smaller particles makes ULPA filters the most expensive filter type.
2. Particles may be filtered in numerous ways due to a filter’s design
Depending on the design of the filter, there are four different ways particles may be filtered.
Straining/sieving. This filtering method catches any particles that are larger than the clearance between the fibers of the filter.
Inertial/impaction. The inertia of the particles forces them out of the airstream, where they get stuck to adhesive fibers.
Interception. Smaller particles get caught in the airstream and are carried towards the filter fiber, which then intercepts them before they can be released back into the air.
Diffusion. Perfect for very small particles, diffusion bombards contaminant particles with air molecules until they go into vibration mode. This vibration makes it much easier for filter fibers to catch even the smallest particles, although it has little impact on larger ones.
3. HEPA filters are the most commonly employed filter in cleanrooms.
HEPA filters were first invented in 1941 to protect scientists from Alpha particles created as they developed the atomic bomb. They are made from pleated layers of media paper, in which particles then get trapped. Filters must remove a minimum of 99.97% of particles before they can be designated as HEPA.
4. Filter maintenance should be performed regularly depending on the filter.
Since filters for cleanrooms can be used 24/7, they may deteriorate faster than other types of equipment. On average, pre-filters should be replaced six times a year and HEPA filters should be replaced every three years. However, factors such as cleanroom location, nearby construction, and air pollution can impact these maintenance schedules.
5. People are the biggest risk to proper cleanroom filtration.
While filters keep air filtered, humans pose the biggest risk to cleanroom filtration. It is the responsibility of the employee to reduce the risk of contamination and ensure that the air is being properly filtered. Proper clothing such as gowns, coveralls, gloves, face masks, and goggles can help prevent contamination from employees. Cleanrooms may also incorporate sinks, showers, and other disinfection equipment in entry and/or exit areas for applications with very high cleanliness standards.
Filtration Products Available at Liberty Industries
We offer a wide range of quality filtration products to suit every need. Some of our most popular products include:
HEPA/ULPA filters. Our filters are engineered to meet ISO 14644-1.
Pre-filters. These non-woven, fine-fibered media pre-filters allow you to upgrade preexisting systems easily.
Charcoal filters. Charcoal filters used primarily for odor reduction.
Work With Liberty Industries
Implementing a high-quality filtration system is vital to the functionality of any cleanroom. To learn more about how our experts can help you design or optimize your cleanroom, contact us or request a quote today.
As a manufacturer and distributor of top-of-the-line cleanrooms and contamination control products, Liberty Industries, Inc. serves as a one-stop shop for all cleanroom needs. Our expert team assists in every aspect of cleanroom creation—from design to construction and assembly—to provide custom-tailored solutions to a wide range of industries. Whether a customer requires a standard or highly specialized area; a positive air pressure cleanroom or negative air pressure cleanroom, we can meet their needs.
Positive Pressure vs. Negative Pressure Cleanrooms: Similarities and Differences
When planning or preparing for a cleanroom installation, one of the most significant design considerations is whether it features a positive air pressure or a negative air pressure configuration. This factor relies heavily on the specifications of the intended application.
Positive Air Pressure Cleanrooms
A positive air pressure cleanroom has an air pressure level that is greater than that of the surrounding environment. This is achieved through the use of an HVAC system, which pumps clean, filtered air into the structure. When the door of the cleanroom is opened or if the cleanroom experiences a structural breach, the pressure disparity forces the clean air out rather than allowing unfiltered, potentially contaminated air in.
Positive air pressure cleanrooms are most commonly used in applications where keeping contaminants—such as dirt or debris—away from the contents of the cleanroom is critical. For example, it can be used to protect immunocompromised patients in hospitals or sensitive products such as microchips during the manufacturing process.
Negative Air Pressure Cleanrooms
In contrast to a positive air pressure cleanroom, a negative air pressure cleanroom maintains an air pressure level that is lower than that of the surrounding room. This condition is achieved through the use of an HVAC system that continuously filters air out of the room, pumping clean air into the room near the floor and sucking it back out near the ceiling.
Negative air pressure cleanrooms are used to keep contaminants contained within the enclosed work environment. If opened or breached, the pressure disparity forces air into the cleanroom, preventing contaminants from escaping. For the room to function properly, all windows and doors must be fully sealed and outtake filters must be installed.
This type of cleanroom commonly finds application in the biochemical, pharmaceutical, or medical industries. Industry professionals use it as an isolation chamber when testing or working with potentially harmful compounds and separating contagious patients to help prevent the spread of illness.
Similarities Between Positive Pressure and Negative Pressure Cleanrooms
Although the functions of positive pressure and negative pressure cleanrooms are quite different, they are some similarities between the two. For example, both types require the use of:
Powerful HEPA filters, which, along with the other HVAC system parts, need careful maintenance
Self-closing doors and properly sealed windows, walls, ceilings, and floors to facilitate the maintenance of appropriate air pressure levels
Multiple air changes per hour to ensure proper air quality and pressure conditions
Ante-rooms for employees to change into the required protective clothing and deliver the necessary materials and equipment
In-line pressure monitoring systems
Leave it to the Experts at Liberty Industries to Design & Construct Your Cleanroom!
Whether you need a positive air pressure or negative air pressure cleanroom, an experienced cleanroom manufacturer and distributor, such as Liberty industries, can ensure the design, development, and delivery of a solution that meets your needs. At Liberty Industries, our experts have full working knowledge of the entire cleanroom design and construction process, from cleanroom materials and best practices to the HVAC equipment needed for different types of applications. We also offer a variety of cleanroom accessories and equipment, including shoe brush machines, Tacky Mats ® and air showers.
No matter what type of cleanroom you need, we’re your one-stop shop to getting the perfect solution. For additional information about our cleanroom capabilities or to discuss your cleanroom specifications with one of our experts, contact us or request a quote today.
