What a HEPA grade states
Particle filters do not catch all sizes equally. Large particles are caught by impaction on the fibres, and very small ones by diffusion as they wander in the air stream and hit the fibres. In between lies a size where both mechanisms are weakest, the most penetrating particle size, abbreviated MPPS. Because the MPPS is where the filter is at its worst, testing at that size gives the most honest figure. The standards EN 1822 in Europe and ISO 29463 internationally classify filters by their efficiency at the MPPS, and the grade is the result.
Vacuum sheets most often cite grades H11 to H14. The published overall efficiency floors at the MPPS are:
| Grade | Minimum efficiency at MPPS (overall) | Typical use in vacuums |
|---|---|---|
| H11 | At least 95% | Entry HEPA-type exhaust filters on mainstream household models |
| H12 | At least 99.5% | Upper mainstream and pet-oriented models |
| H13 | At least 99.95% | Premium household, some commercial machines |
| H14 | At least 99.995% | Specialist commercial and industrial exhaust stages |
The wording of the grade should always be the EN 1822 designation and the percentage floor. A sheet that says only "HEPA filter" is making a loose statement; the grade is the part that can be verified.
How the test works
In the test the filter media are first scanned to find the MPPS, usually in the range of a tenth to a few tenths of a micrometre, using a fine aerosol and a particle counter upstream and downstream. The efficiency at that size is then measured on the whole filter element, along with a leak scan for the higher grades, so that a pinhole or a poorly sealed edge cannot hide behind an average. This is why grades H13 and above are tested per filter element for leaks, while lower grades rely on sampling. The result is a figure for the element on a test rig with controlled airflow, not for the vacuum cleaner in a room.
What the grade does not tell you
- Whole-machine exhaust. Air can leak around the filter frame, through housing seams or past a poorly seated cover. A sealed system is a design and assembly property, and the grade of the media alone cannot show it.
- Airflow cost. Higher grades have denser media and add resistance. A machine designed around an H13 filter has to move enough air through it, or suction falls.
- Life of the media. Efficiency is quoted for clean media. As the filter loads with dust, resistance rises and, in pleated designs, efficiency can change as the cake builds.
- Health claims. A filter grade is a physical measurement. It is not a statement of medical effect, and sheets should not translate it into one.
Grade, media type and washability
Filters in a vacuum come in several media families, and the grade lives on only one of them. Foam and felt pre-filters protect the motor and are washable, but they carry no EN 1822 grade. Paper and non-woven cartridge media can reach the middle grades if they are made and tested as filter media. Glass-fibre and synthetic HEPA media reach H13 and H14, and are usually pleated into a frame to give enough area. Some washable "HEPA-type" filters exist, but washing changes the fibre structure and the seal, so a washable element should be tested as a washable element and its grade should be stated after the specified number of washes, not only when new. If a sheet claims a grade for a washable filter, ask what the claim is based on.
A practical consequence for spare parts: if the filter is part of the performance claim, the replacement filter has to meet the same grade. A cheaper unrated replacement quietly voids the claim, so the spare part list should carry the grade and the part number, and the packaging should say how often to change or wash it.
Where the filter sits in the machine
A vacuum has a chain: a pre-filter or screen to stop large debris, a separation stage (bag or cyclone), a motor protection filter, and often a final exhaust filter. The HEPA element is typically at the end of the chain, where it protects the room air, or it is combined with the motor filter as a single cartridge. In sealed-system designs the whole airway is gasketed so that all air must pass through the final filter. In non-sealed designs the HEPA element sits in the path but air can bypass it. The design choice is as significant as the grade. The vacuum filter and HEPA page shows the six parts of a typical cartridge, including the pleated media, frame, end caps, seal and optional carbon layer.
Choosing a grade for a program
The right grade depends on the market and the product positioning, not on the highest number available.
- Decide whether the filter is a selling point. Pet-hair and household premium lines often carry H12 or H13 media; mainstream lines may use H11 or a standard filter.
- Fix the airflow budget. A denser grade needs a larger filter area or a stronger motor to preserve suction.
- Decide on washable or replaceable media, and plan the spare part line, since filters are a recurring item.
- Define the seal. Ask the plant whether the exhaust path is sealed, and how it is checked on the line.
- Ask for the supplier's grade test report for the media, and a sampling plan for incoming filters. Per-project verification is agreed and confirmed in writing.
Filter media is bought from specialist partner suppliers, not made by the desk; the desk's role is to match a plant with a filter source and to include filter checks in quality control. For the surrounding material questions, see the spec reading note for the whole sheet and the suction and airflow note for how filter resistance moves the working point. Quantities for filters are usually counted in thousands; see MOQ and lead time, or send a brief through the quote form.