Air Filtration Science
Understand the technology behind air purification. From MERV to HEPA, carbon to UV-C - learn how each filter type works and which is right for your needs.
Standards Body: British Standards (BS EN 1822)
UK uses EN standards aligned with EU. MERV is increasingly adopted.
MERV Filters
Minimum Efficiency Reporting Value - the standard rating system for air filters. MERV 13-16 are best for homes.
HEPA Filters
High Efficiency Particulate Air filters capture 99.97% of particles at 0.3 microns. Medical and hospital grade.
Activated Carbon
Adsorbs gases, VOCs, and odours that particle filters miss. Essential for smoke and chemical removal.
UV-C Light
Ultraviolet germicidal irradiation kills bacteria and viruses. Requires sufficient exposure time.
Ionizers
Charge particles to make them stick to surfaces. Can produce ozone - avoid for asthma/COPD.
Electrostatic
Use electric charge to capture particles. Washable but efficiency drops without cleaning.
Understanding Particle Sizes
Different pollutants come in different sizes. Understanding particle sizes helps you choose the right filter:
| Particle | Size (μm) | Min Filter |
|---|---|---|
| Dust mites | 10-40 | MERV 8 |
| Pollen | 10-100 | MERV 8 |
| Mould spores | 3-30 | MERV 11 |
| Bacteria | 0.3-10 | MERV 13 |
| Smoke particles | 0.1-1 | MERV 13+ |
| Fine PM2.5 | <2.5 | MERV 13+ |
| Viruses (on droplets) | 0.1-0.3 | HEPA |
Cost Comparison (🇬🇧 UK)
MERV vs HEPA: Quick Guide
Choose MERV 13-16 When:
- • Budget is a concern
- • General allergy/dust protection
- • HVAC upgrade (check compatibility)
- • DIY box fan builds
- • Smoke and PM2.5 protection
Choose HEPA (H13+) When:
- • Asthma, COPD, or immunocompromised
- • Maximum virus protection needed
- • Nursery or baby's room
- • Healthcare/clinical settings
- • Budget allows for quality unit
Calculate Your Filter Needs
Use our ACH calculator to find the right CADR and filter size for your room. Then compare DIY vs commercial options.