The filter types
HEPA grades such as H13 and H14 are defined by the European standard EN 1822. Higher grades capture more, but also add resistance to airflow, so the system must be designed for them.
| Filter | What it catches | Typical use |
|---|---|---|
| Panel / pre-filter | Large dust and fibres | First stage in almost every system |
| Pleated | Finer dust, pollen | Offices, shops, residential central AC |
| Bag / pocket | Fine dust with high dust-holding capacity | AHUs in offices, malls, factories |
| HEPA (H13, H14) | At least 99.95% to 99.995% of the most penetrating particles | Hospitals, operating theatres, labs, pharma |
| ULPA | Even finer particles | Cleanrooms and critical processes |
Why filters are staged
Systems use a cheap pre-filter in front of finer filters. The pre-filter catches the bulk of the dust so the expensive bag or HEPA filter lasts much longer. Skipping or neglecting the pre-filter is one of the most costly maintenance mistakes.
How often to change filters
- Pre-filters: often every one to three months in dusty conditions.
- Bag and pleated filters: less often, based on pressure drop across the filter.
- HEPA filters: based on pressure readings and validation requirements for critical spaces.
- The reliable signal is the pressure drop across the filter, not the calendar alone.
Scheduled replacement contracts
We supply genuine AAF panel, pleated, bag, HEPA and ULPA filters matched to your units, and can replace them on a schedule so no system runs on clogged filters.
Frequently asked questions
Can I put a HEPA filter in my central AC?
Only if the system is designed for it. HEPA filters restrict airflow far more than standard filters, so the fan and housing must suit them. Ask us before upgrading.
What filter does a hospital operating theatre need?
Typically HEPA filtration at the terminal supply, to the grade the facility's specification requires. We supply AAF HEPA to specification.
Do you supply filters to our existing sizes?
Yes. Send the sizes and grades from your current filters, or a photo of the label, and we will match them.