When it comes to air filtration in professional environments, three abbreviations quickly come up: EPA, HEPA and ULPA. Three terms that may look similar at first glance, but differ significantly in practice. And that choice is anything but arbitrary. Because the wrong filter in the wrong environment can be costly or even dangerous.
In this article, we explain step by step what these filter types are, how they are classified, and — perhaps more importantly — which filter should be used in which environment.
Absolute filters: a class of their own
Before we look at the differences in more detail, it is important to understand that EPA, HEPA and ULPA filters are referred to as absolute filters. They form a separate category, distinct from ordinary air filters used in ventilation and air conditioning.
Conventional air filters are tested and classified according to the ISO 16890 standard. Absolute filters are subject to a stricter European standard: EN 1822, supplemented by the international standard ISO 29463. These higher requirements exist for good reason. After all, absolute filters are used in environments where even the smallest particles pose a serious risk to people, processes or products.
What makes an absolute filter “absolute”?
With conventional air filters, the filtration efficiency is determined as an average across a broad spectrum of particle sizes. With absolute filters, the most critical particle size is measured: the MPPS (Most Penetrating Particle Size). This is the size at which a filter is least efficient. By measuring at exactly that point, you can be certain that the stated efficiency always represents the minimum value, not an average.
EPA: efficient, but not infallible
EPA stands for Efficient Particulate Air. It is the less powerful sibling of HEPA, but by no means unimportant. EPA filters are divided into three classes: E10, E11 and E12, with a minimum filtration efficiency of 85%, 95% and 99.5% respectively, measured at the MPPS.
A key difference from HEPA and ULPA filters is that EPA filters are not tested individually. They are classified on the basis of samples from a production batch, with statistical sampling carried out for filters of the same class. This makes them reliable and cost-effective filters for applications where ultra-fine particles do not need to be retained.
When do you choose EPA?
- Pre-filtration stages in complex air handling systems
- Workshops and industrial environments with dust exposure
- Food industry and precision manufacturing lines
- Pharmacy and precision industry (class E12)
HEPA: the gold standard in critical environments
HEPA stands for High Efficiency Particulate Air and is the world’s best-known filter class for high-quality air purification. HEPA filters are divided into two classes: H13 and H14, with a minimum overall separation efficiency of 99.95% and 99.995% respectively.
What distinguishes HEPA from EPA is not only the higher filtration efficiency, but also the way it is tested. Every HEPA filter is tested individually and provided with its own test certificate. This certificate states both the overall efficiency (total performance) and the local efficiency (performance at the weakest point). This provides absolute certainty about the quality of each individual filter element.
HEPA filters effectively capture bacteria, mould spores, fine dust and aerosols, as well as viruses. This makes them indispensable in environments where air quality has a direct impact on health and safety — think operating theatres, intensive care units, pharmaceutical production facilities and cleanrooms.
When do you choose HEPA?
- Operating theatres and care environments (H13 is the standard requirement)
- Microbiological laboratories and research facilities
- Pharmaceutical production in accordance with GMP guidelines
- Cleanrooms in the electronics industry
- Quarantine stations and isolation rooms (H14)
ULPA: for the most demanding environments
ULPA stands for Ultra Low Penetration Air. Where HEPA already delivers exceptional performance, ULPA goes one step further. ULPA filters are divided into classes U15, U16 and U17, with minimum efficiencies of 99.9995%, 99.99995% and 99.999995% respectively. To put that into perspective: an H14 HEPA filter lets through a maximum of 5 particles per million at full load. A U17 ULPA filter lets through only 1 in 100 million.
Just like HEPA filters, ULPA filters are individually tested using a scan test, in which every square centimetre of the filter surface is examined for leaks and local deviations.
When do you choose ULPA?
- Chip manufacturing and microelectronics (particles of 0.1 µm and smaller are already harmful)
- Pharmaceutical isolators and aseptic production processes
- Aerospace
- Nuclear facilities
- Nanotechnology and high-grade research environments
How do you choose the right filter type?
The choice between EPA, HEPA or ULPA depends on several factors. The filtration efficiency is one of them, but certainly not the only one. A higher filter class also means greater air resistance (pressure drop), which affects energy consumption and the sizing of your ventilation system.
Relevant factors when selecting:
- The type of environment: which particles or micro-organisms need to be retained?
- The applicable standards or guidelines for your industry (GMP, ISO 14644, healthcare guidelines)
- The pressure drop and permissible energy consumption of your system
- The desired service life and maintenance interval
- Dimensional and connection specifications of your existing filter housings or systems
At TripleAir Technology, we develop and produce EPA, HEPA and ULPA filters entirely in-house, using exclusively European components. Every HEPA and ULPA filter is individually tested and provided with its own test report. This means you can be certain not only of the class, but also of the individual filter element you are installing.
Would you like to find out more about a custom filter?
Do you have a specific question about air filtration in your environment, or would you like to know which filter type best suits your system? Feel free to contact us. We are happy to think along with you, from a straightforward replacement to a complex custom solution.