HEPA vs MERV Filters: Complete UK Guide 2025

Choosing between HEPA and MERV filters is critical for effective air purification. This guide explains the key differences, UK standards, and which filter type suits your needs.

What is a HEPA Filter?

High-Efficiency Particulate Air (HEPA) filters are the gold standard for air purification.

US Standard (True HEPA): Captures 99.97% of particles at 0.3 microns
UK/EU Standard (EN 1822): Captures 99.95% of particles at MPPS (Most Penetrating Particle Size)
Ratings: H13 (99.95%), H14 (99.995%)

What is a MERV Filter?

Minimum Efficiency Reporting Value (MERV) is a rating system from 1-16 developed by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers).

MERV Rating Scale:

MERV 1-4: Basic residential filters (dust, pollen) - Not recommended
MERV 5-8: Better residential (mould spores, pet dander) - Minimal protection
MERV 9-12: Superior residential (captures 80-90% of particles 1-3 microns)
MERV 13-16: Hospital-grade (90%+ capture of 0.3-1 micron particles)

Key Differences Explained

Feature	HEPA H13	MERV 13
Particle Capture (0.3-1μm)	99.95-99.97%	90%
Cost	£30-80	£15-30
Airflow Resistance	High (needs powerful fan)	Moderate
Best For	Allergies, asthma, viruses	General air quality, smoke
Lifespan	12-18 months	3-6 months

UK Filter Standards (EN 1822:2019)

In the UK and Europe, filters follow ISO and EN standards:

EPA (Efficient Particulate Air): E10 (85%), E11 (95%), E12 (99.5%)
HEPA (High-Efficiency): H13 (99.95%), H14 (99.995%)
ULPA (Ultra-Low): U15 (99.9995%), U16 (99.99995%), U17 (99.999995%)

Which Filter Should You Choose?

Choose HEPA H13 If You Have:

Severe allergies or asthma
Need virus/bacteria filtration
Live in high-pollution area (London, Manchester)
Immunocompromised household members
Budget for higher initial and replacement costs

Choose MERV 13 If You Have:

General air quality concerns
Pet dander or odour issues
Seasonal wildfire smoke exposure
Budget constraints (£15-30 vs £30-80 per filter)
DIY air purifier projects (Corsi-Rosenthal boxes)

Performance Comparison

Particle Size Capture Rates:

10+ microns (pollen, dust): Both ~100%
3-10 microns (mould spores): HEPA 100%, MERV 13 90-95%
1-3 microns (fine dust): HEPA 99.97%, MERV 13 85-90%
0.3-1 micron (bacteria): HEPA 99.97%, MERV 13 75-85%
<0.3 micron (viruses): HEPA 99.97%, MERV 13 50-75%

Common Misconceptions

Myth: "HEPA-Type" or "HEPA-Like" is the Same

FALSE. Only "True HEPA" or "H13" meets the 99.97%/99.95% standard. "HEPA-type" is marketing language for lower-efficiency filters (often 85-90%).

Myth: MERV 16 = HEPA

FALSE. MERV 16 captures ~95% at 0.3 microns. HEPA H13 captures 99.95%. That 5% difference matters for allergens and viruses.

UK Availability

HEPA H13 Filters: 3M Filtrete, Honeywell, Dyson (proprietary), Blueair
MERV 13 Filters: 3M Filtrete MPR1900, Nordic Pure, FilterBuy UK
Where to Buy: Amazon UK, Screwfix (HVAC section), specialist HVAC suppliers

Bottom Line

For most UK homes, MERV 13 offers excellent value with 85-90% particle capture at 1/3 the cost of HEPA. For severe allergies, asthma, or immune concerns, invest in true HEPA H13. Either way, proper sizing (CADR) and regular replacement matter more than filter type.