08 Jul ULPA Filters vs HEPA Filters: What’s the Difference?
In the world of cleanrooms, air quality can make or break an operation, whether it’s in manufacturing or scientific research. But when it comes to choosing between ULPA and HEPA filters, how can you be sure which one is right for your space? In this article, we’ll take a look at ULPA filters and HEPA filters to explore their similarities, differences, and more.
What is a HEPA Filter?
A high-efficiency particulate air (HEPA) filter is an advanced filtration device used to capture at least 99.97% of particles that are 0.3 micrometers in diameter. This size is considered the most penetrating particle size (MPPS), meaning particles smaller or larger than 0.3 micrometers are captured even more efficiently.
HEPA filters are made from a mat of randomly arranged fibers, which can be composed of various materials, such as borosilicate glass fibers or other synthetic materials like polypropylene. The density and diameter of the fibers, along with the thickness of the filter, all contribute to its efficiency.
They are used in many cleanroom applications, including medical cleanrooms, semiconductor cleanrooms, and more, and they are even sometimes used in residential air purifiers. In general, they help reduce allergens, dust, and other airborne particles.
What is an ULPA Filter?
Ultra-low penetration air (ULPA) filters, on the other hand, capture at least 99.9995% of particles that are 0.12 micrometers in diameter. While the exact most penetrating particle size (MPPS) can vary, ULPA filters are extremely efficient at capturing very small particles, even more so than HEPA filters.
ULPA filters are made from similar materials to HEPA filters, but they have a higher density of fibers and a finer mesh. Both of these features allow ULPA filters to trap smaller particles more effectively.
ULPA filters are typically used in cleanrooms, but only those which are very strict, such as ISO Class 5 and above.
What are the Differences Between ULPA Filters vs HEPA Filters?
The differences between ULPA and HEPA filters can be subtle, but it’s important for cleanroom engineers to select the right filters when deciding to build a cleanroom. Here are a few of the main ways in which ULPA and HEPA filters differ.
| HEPA Filters | ULPA Filters | |
|---|---|---|
| Filtration Efficiency | Captures 99.97% of particles of 0.3 micrometers. | Captures 99.9995% of particles of 0.12 micrometers. |
| Airflow Resistance | Lower resistance, less impact on airflow. | Higher resistance, significantly impacts airflow. |
| ACH Impact | Maintains higher ACH, supports cleanroom cleanliness. | Reduces ACH, potentially making spaces less clean. |
| HVAC Efficiency | Less impact on HVAC systems. | Reduces HVAC efficiency, requires more energy and resources. |
| Cost | Generally less expensive. | Often more than 30% more expensive. |
| Lifespan | Lasts up to 10 years. | Lasts 7-8 years, shorter lifespan. |
| Applications | Used in ISO Class 5-8 cleanrooms; common in food, pharmaceuticals, and semiconductors. | Used in ISO Class 5 and stricter cleanrooms; often used in aerospace and semiconductor manufacturing. |
Filtration Efficiency
Simply put, ULPA filters capture more particles than HEPA filters. As we mentioned before, HEPA filters can capture 99.97% of particles of 0.3 micrometers, and ULPA filters can capture 99.99% of particles that are 0.12 micrometers in diameter.
This doesn’t seem like a huge difference at first glance, and for a lot of practical purposes, it isn’t.
However, in cleanroom applications that require ISO Class 1-5 spaces, ULPA filters will be necessary to meet standards. Ultimately, ULPA filters can trap smaller particles more efficiently than HEPA ones.
Airflow Resistance
Though we’ve just established that ULPA filters capture particles more efficiently, this comes at a cost: reduced airflow.
In truth, both HEPA and ULPA filters impact airflow, but ULPA filters create far more resistance.
Such resistance can negatively affect air changes per hour (ACH), which is a measure of how many times the air within a defined space is replaced each hour. A high number of ACH is what makes cleanrooms maintain their cleanliness, so ironically, ULPA filters can actually make a space less clean.
And even when ULPA filters are used, this resistance can reduce the efficiency of HVAC systems, which will require more energy and resources to keep the cleanroom clean.
Cost and Maintenance
Then of course, there’s the financial costs. ULPA filters are often significantly more expensive than HEPA ones, often more than 30% more expensive.
Lifespan
Similarly, ULPA filters have a much shorter lifespan compared to HEPA filters, which of course, adds to their overall cost. An ULPA filter may last seven or eight years, while a HEPA filter may last up to ten years under similar conditions.
Applications
HEPA filters are typically used in many ISO cleanroom classes, but especially in ISO Class 5 through ISO Class 8 spaces. They are used in the food and beverage industry, pharmaceuticals, semiconductors, and more.
ULPA filters, on the other hand, are usually used in ISO Class 5 and stricter cleanrooms. They are perfect for spaces where a few tiny particles can cause major disruptions, such as aerospace and semiconductor manufacturing.
The Bottom Line
While both HEPA and ULPA filters are efficient at trapping tiny particles, ultimately, ULPA filters do it better. That being said, they are often not the right choice because of their airflow resistance, cost, and shorter lifespan. Choosing between HEPA filters and ULPA filters depends in large part on your specific requirements and budget.
Considering building a cleanroom and need expert advice on filtration? Contact Allied Cleanrooms today to get a free quote and ensure your cleanroom is equipped with the best air filtration technology available.