According to the International Organization for Standardization (ISO) 14644, the standard that regulates cleanrooms, a cleanroom is “a room in which the concentration of airborne particles is controlled and which is constructed and used in a manner to minimize the introduction, generation, and retention of particles inside the room.”
In less formal, non-ISO terms, cleanrooms are spaces that must be protected from the damage that the infiltration of minute sub-micron-sized particles and microbes can cause.
Cleanrooms must be cleaned by trained hospital environmental Services (EVS) and/or cleanroom cleaning technicians to control particulate matter. Maintaining a cleanroom also requires the correct filtration, especially in complex facilities. With this in mind, let’s take a closer look at cleanrooms and the type of filtration required.
Where Cleanrooms Are Found
Cleanrooms are found in facilities where microbes from seriously ill patients cannot be allowed to escape, for example. Cleanrooms are also found in a vast array of food, drug, computer chip, and other manufacturing and life sciences facilities where the most minute particulate can harm the quality of the final product, cause production shutdowns, and even lead to lawsuits. Yet not all cleanrooms are equal.
ISO Ratings
The level of cleanliness required—known as the cleanliness standard—is based on the amount of particulate allowed to exist in a cleanroom per cubic meter. The level varies based on the room’s usage, and each level is given a different ISO classification from 1 through 9. The “dirtiest” cleanroom must meet the ISO 9 standard, allowing it to harbor one million micron-sized particles per cubic meter. The “cleanest” cleanroom is ISO 1, which mandates 1,000 or fewer micron-sized particles per cubic meter. ISO 1 cleanrooms are often found in life sciences and electronics that require nanotechnology. Medical cleanrooms, including research, medical device, and pharmaceutical facilities that require sterilization, are in the ISO 5 to 7 level. Here it is good to remember that even ISO 9 level is far cleaner than an average room, suggesting the need for above-average room filtration.
Merv 13 Is Great—But Not Enough
One major step towards good air filtration is the use of an air filter with a minimum efficiency reporting value (MERV) of 13 or higher for your entire facility. This can help reduce the overall particulate matter in a building. However, a MERV 13 filter traps less than 75% of 0.3 to 1.0-micron particulates—not enough to meet cleanroom ISO regulations. Moreover, many existing HVAC system fans can’t handle the increased load on the fan that the finer MERV 13 filter causes, which can reduce airflow.
HEPA and ULPA Filters
ISO 14644 requires cleanrooms to have a high-efficiency particulate air (HEPA) or ultra-low particulate air (ULPA) filter. HEPA filters are rated for 99.97% efficiency on 0.3-micron particles. This means the filter can only allow three out of every 10,000 0.3 micron particles to pass through. To put this in perspective, the average human hair is 80 to 100 microns in diameter. This means a HEPA filter can even trap pollutants invisible to the eye, such as viruses and bacteria. The ULPA filter captures particles down to 0.128 microns in diameter.
The 0.3 and 0.128 microns are actually the lowest levels of the filters’ filtration capabilities. For example, HEPA must filter at an efficiency rate of 99.97% at 0.3 microns because 0.3 microns are the hardest size for the filters to capture. The efficiency rate can be even better for collecting particles larger or smaller than 0.3 microns! This seems counterintuitive but think of the HEPA filter like a fishing net. Particles larger than 0.3 microns can’t make it through the holes in the net/filter. Based on this, it would seem logical that small particles should be able to pass through easily. However, particles smaller than 0.3 microns are subject to what is scientifically called Brownian motion. In simple terms, what this means is the particles are so tiny they get bounced around by gas molecules, hitting the filter in zigzag patterns. So rather than hitting the holes straight on and sailing quickly through, they come from different directions and get caught in the filter’s fibers.
Making the Grade
All HEPA filters must meet the minimum 0.3 micron collecting requirement. From there, they are graded based on their increased efficiency. The higher the grade, the more efficient the filter. Most HEPA filters are graded between H10 and H12, meaning they can trap 95% to 99.5% of particles that are 0.1 microns in diameter. H13 and H14 are medical-grade filters capable of trapping 99.95% and 99.995% of particles 0.1 microns in diameter, respectively.
While all cleanrooms require a HEPA filter, ISO standard 14644 does not stipulate which grade of HEPA filter must be used. The selection depends on your specific cleanroom, and filtration needs to reach the amount of particulate allowed per cleanroom category. For example, ISO 8 may use a lower grade HEPA filter than ISO 1 unless the ISO 8 cleanroom is especially full of particulate matter that may require greater filtration (higher grade HEPA filter) to reach the minimum particulate matter allowed.
A Commercial Cleaning Services Provider With 50 Years of Cleanroom Maintenance Experience
Servicon is Southern California’s leading hospital EVS, facility management, and commercial GMP cleanroom cleaning provider for complex facilities. We have spent 50 years maintaining all levels of cleanrooms in the healthcare, aerospace, and life sciences industries. Contact us today to find out more about our services or to get answers to your cleanroom or other facility maintenance questions.
