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What Is a HEPA Filter — and Does Filter Grade Actually Matter?

Published 11 April 2026 · 19 min read · Karban Envirotech

What is a HEPA filter — grades, efficiency and why it matters for Indian homes

In This Guide

1. What HEPA Actually Means — and the Standard Behind It

2. HEPA Filter Grades Explained: From H10 to H14

3. What a HEPA Filter Captures — and What It Cannot

4. Why Indian Homes Specifically Need HEPA-Grade Filtration

5. Filter Grade vs CADR — Which Number Matters More?

6. What to Check When Buying a HEPA Air Purifier in India

7. HEPA Filter Maintenance and Replacement in Indian Conditions

8. Key Takeaways

9. Frequently Asked Questions

10. Sources

When shopping for an air purifier in India, the word "HEPA" appears on nearly every product listing. Budget purifiers under ₹5,000 claim "HEPA-type" filters. Mid-range models advertise "True HEPA." Premium devices specify H13 grade filtration. Without a framework for what these terms actually mean, buyers have no way to separate genuine filtration from marketing language — and in India, where indoor PM2.5 levels regularly exceed ten times the WHO guideline, the difference between a real HEPA filter and a basic mesh filter is not cosmetic.

HEPA is a performance standard, not a brand name. The standard has multiple grades, each capturing different percentages of particles at different sizes. A filter labelled "HEPA-type" in a budget purifier may capture 70–80% of PM2.5. A genuine H11 HEPA-class filter captures 99.95% of particles at the most penetrating particle size. The difference determines whether the device is actually cleaning the air you breathe or simply moving it around.

This article explains the HEPA standard from the ground up: what each filter grade means, what HEPA can and cannot capture, why filter grade is only one part of the buying decision, and what Indian households specifically need to look for. If you are also trying to understand why indoor air quality in Indian cities is often significantly worse than most residents expect, the case for genuine HEPA filtration becomes even clearer.

1. What HEPA Actually Means — and the Standard Behind It

HEPA stands for High Efficiency Particulate Air. The term originated in the US during the 1940s when the Atomic Energy Commission developed high-efficiency filters for nuclear facilities. The concept has since become a global performance benchmark adopted by regulatory bodies and standards organisations worldwide.

The defining requirement: a filter qualifies as HEPA-class or above if it captures a high percentage of airborne particles at 0.3 microns in diameter — the "most penetrating particle size" (MPPS). The reason 0.3 microns is the hardest size to capture is counterintuitive. Very large particles are stopped by impaction (they hit filter fibres directly). Very small particles are stopped by diffusion (they move erratically due to Brownian motion and collide with fibres). Particles at exactly 0.3 microns are too large to diffuse effectively and too small for reliable impaction — making them the most likely to slip through.

The international standard used in India and Europe is EN 1822, published by the European Committee for Standardisation. Under EN 1822, air filters are classified by their ability to capture particles at MPPS. Any air purifier sold in India with BIS (Bureau of Indian Standards) certification must meet the filter performance specification it claims on the label.

2. HEPA Filter Grades Explained: From H10 to H14

EN 1822 classifies filters from E10 to U17, covering Efficient Particulate Air (EPA), High Efficiency Particulate Air (HEPA), and Ultra Low Penetration Air (ULPA) grades. For residential air purifiers, the relevant range is H10 to H14:

Grade	Classification	Efficiency at MPPS	What This Means in Practice
H10	HEPA-class	≥85%	Captures most PM2.5, pollen, mould spores
H11	HEPA-class	≥95%	Captures nearly all PM2.5, bacteria-sized particles
H12	HEPA-class	≥99.5%	Very high PM2.5 capture, most bacteria
H13	True HEPA	≥99.95%	Medical-grade; standard in hospital air handling
H14	True HEPA	≥99.995%	Cleanroom and pharmaceutical standard

H10–H12 (HEPA-class) are appropriate for residential use. They capture PM2.5, PM10, most bacteria, mould spores, pollen, and dust mite allergens at efficiencies that meaningfully reduce indoor pollution concentrations over repeated air cycles. Their filter media is less dense than H13/H14, which means they impose less resistance on airflow — allowing the purifier's motor to deliver higher CADR.

H13–H14 (True HEPA) are the standard in hospitals, pharmaceutical manufacturing, and cleanrooms. In a residential context, the incremental filtration benefit over H12 is real but smaller than the grade numbers suggest — an H13 filter in a weak motor may deliver less clean air per hour than an H11 filter in a powerful motor, because the denser filter media restricts airflow.

"HEPA-type" or "HEPA-style" is not a grade under EN 1822. These terms appear on products without a verified grade specification. There is no regulatory minimum for what a "HEPA-type" filter must capture. The US EPA explicitly notes that "HEPA-type" filters are not certified to the same standard as rated HEPA filters.

3. What a HEPA Filter Captures — and What It Cannot

A HEPA filter is a physical barrier made of a mat of randomly oriented fibres — typically fibre glass. Particles are captured through three mechanisms working simultaneously:

Impaction: Large particles (above approximately 1 micron) travel in a straight line through the airstream, cannot follow the air around filter fibres, and impact directly into them.

Interception: Medium particles follow the airstream but contact a fibre as they flow near it, adhering by electrostatic attraction or moisture.

Diffusion: Very small particles (below approximately 0.1 micron) move erratically due to Brownian motion, increasing their contact probability with filter fibres.

What HEPA captures effectively:

PM2.5 and PM10 — dust, combustion particles, construction dust · Pollen (10–100 microns) · Mould spores (1–30 microns) · Bacteria (typically 0.3–5 microns) · Dust mite allergens · Pet dander · Tobacco smoke particles

What HEPA does NOT capture:

Volatile Organic Compounds (VOCs) — formaldehyde, benzene, xylene from furniture and paint · Odours · Carbon monoxide and nitrogen dioxide · Radon gas · Viruses below 0.1 micron (though viruses often attach to larger particles and are captured secondarily)

This distinction matters enormously for Indian homes. Understanding what PM2.5 is and why it poses health risks in Indian homes addresses the particle side. But VOCs — particularly formaldehyde off-gassing from MDF furniture, plywood, and fresh paint — require an activated-carbon filter stage to adsorb. No HEPA filter grade, however high, captures gases. A multi-stage purifier with both HEPA and activated-carbon stages is the complete solution for a home with both particle and chemical pollutant sources.

PM2.5, VOCs, humidity, and outdoor infiltration together make up the full indoor air quality picture — covered in our guide to indoor air quality in Indian homes.

4. Why Indian Homes Specifically Need HEPA-Grade Filtration

India's outdoor PM2.5 average of 50.6 µg/m³ in 2024 (IQAir World Air Quality Report) is approximately ten times the WHO's annual guideline of 5 µg/m³. But outdoor levels are only part of the picture. The US EPA and multiple Indian research studies confirm that indoor PM2.5 concentrations can be two to five times higher than outdoor levels depending on indoor pollution sources.

The CPCB's National Ambient Air Quality Monitoring Programme tracks PM2.5 across 100+ Indian cities. Delhi-NCR, Lucknow, Patna, and Kanpur regularly post annual PM2.5 above 90 µg/m³ — the threshold for "Poor" on the CPCB India AQI scale (AQI 201–300). Mumbai, Pune, Bengaluru, and Hyderabad see regular Moderate readings (AQI 101–200) during monsoon and winter seasons.

India's specific indoor pollution profile compounds the problem:

Cooking emissions. High-heat Indian cooking on gas burners generates significant PM2.5 and carbon monoxide even when windows are open. The Ministry of Health and Family Welfare's data confirms that a single gas burner cooking episode in a closed kitchen can push indoor PM2.5 above 200 µg/m³ for 20–30 minutes — the "Very Poor" category on the CPCB India scale (AQI 301–400).

Incense and agarbatti. Burned daily in millions of Indian homes, agarbatti produces ultrafine particles below 1 micron — in the range where HEPA diffusion capture is critical. A 2025 Frontiers in Public Health study on indoor air quality in Delhi Metropolitan City confirmed elevated bioaerosol and fine particle counts in homes where incense was regularly used.

New construction and renovation. India's housing boom means many households are in freshly built or renovated apartments. New MDF furniture, particleboard, and construction adhesives off-gas formaldehyde at elevated levels for 6–12 months after installation. The WHO classifies formaldehyde as a Group 1 carcinogen. An H11 HEPA-class filter with an activated-carbon stage addresses both the particulate and the chemical load.

Seasonal pollution spikes. Diwali firecrackers create acute PM2.5 spikes reaching 500–900 µg/m³ in northern Indian cities — in the Severe category on the CPCB India scale (AQI 401–500). In these conditions, the air change rate (how many times the purifier processes the room's air per hour) determines how quickly indoor concentrations are brought down.

A basic mesh filter or "HEPA-type" filter cannot perform adequately under these conditions. A rated HEPA-class filter at H11 or above, in a device with sufficient CADR, is the functional minimum.

5. Filter Grade vs CADR — Which Number Matters More?

This is the question most buyers get wrong. A higher filter grade does not automatically mean better air quality outcomes in a real room.

CADR (Clean Air Delivery Rate) measures the volume of genuinely cleaned air delivered per hour in m³/h. It is the combined result of filter efficiency and the volume of air the motor pushes through the filter per hour. An H13 True HEPA filter in a weak motor that delivers 80 m³/h of cleaned air will perform dramatically worse in a 200 sq ft Indian bedroom than an H11 HEPA-class filter in a powerful motor delivering 250 m³/h — because air that never reaches the filter is never cleaned.

For a 200 sq ft room with a 9-foot ceiling (approximately 167 m³ of air), a CADR of 250 m³/h means the room's air passes through the filter approximately 1.5 times per hour. Most air quality guidelines recommend 2–5 air changes per hour for effective particulate reduction. The CADR number is what determines whether those air changes happen.

The denser construction of H13 and H14 filters also increases air resistance. In a purifier not engineered specifically for a high-grade filter, running an H13 filter can reduce motor airflow by 20–30% compared to an H11 filter, partially offsetting the grade advantage.

The practical conclusion: verify the filter grade is specified (not "HEPA-type"), but weight CADR equally in your purchase decision. For a comprehensive breakdown of why CADR is the number that determines whether purification is real, see our dedicated guide.

6. What to Check When Buying a HEPA Air Purifier in India

Filter grade must be specified. H10, H11, H12, H13 — not "HEPA-type," "HEPA-style," or "99% efficiency" without a grade citation. If the product listing does not specify an EN 1822 grade, treat the claim with caution.

CADR must be published. A minimum of 200 m³/h for a 150–200 sq ft room. For a 250–300 sq ft living room, look for 250 m³/h or above. Products that do not publish CADR are either untested or aware that the number is uncompetitive.

BIS certification for Indian compliance. Any purifier sold in India should carry BIS certification. This ensures the product meets Indian electrical safety standards and that filtration claims have been independently verified.

Multi-stage filtration for VOC removal. If your home has new furniture, fresh paint, or recent renovation, confirm the purifier includes an activated-carbon stage in addition to the HEPA filter. HEPA alone does not address formaldehyde and other off-gassing chemicals.

Running cost calculation. Purifier wattage × daily hours × ₹10/unit (standard India electricity rate). A 45W purifier running 12 hours per day costs ₹5.40/day or approximately ₹1,971/year. A 22W BLDC+ motor at the same runtime costs ₹2.64/day — ₹964/year. For a device intended to run continuously through Indian summers, motor efficiency matters significantly over the appliance's lifetime.

AQI monitoring to verify results. Smart air purifiers with built-in AQI sensors — like the Karban Airzone, which shows live AQI readings and historical data in the mobile app and displays an AQI colour indicator on the product itself — let you confirm in real time that the filter is making a measurable difference, rather than assuming it is.

The KARBAN Airzone uses an H11 HEPA-class filter with an antimicrobial/antibacterial coating, delivering a verified CADR of 250 m³/h from a ceiling-mounted position. The antimicrobial coating reduces bacterial growth on the filter surface between replacement cycles — a relevant consideration in humid Indian climates where filter media can accumulate microbial load. It is also worth noting that standard split ACs do not purify air — their basic mesh filters are designed to protect internal coils, not to capture PM2.5 or bacteria.

7. HEPA Filter Maintenance and Replacement in Indian Conditions

A HEPA filter in Indian urban conditions accumulates particulate load significantly faster than in cleaner environments. Most manufacturers calculate replacement intervals against average global pollution levels — which are dramatically lower than Delhi, Mumbai, or Bengaluru's daily reality. Understanding when and how to replace the filter is part of getting full value from a purifier.

How quickly does a HEPA filter load in Indian conditions?

In a city with average PM2.5 above 35 µg/m³ — which includes most Indian metros — a HEPA filter running 8–12 hours per day will typically show visible grey discoloration within 4–6 months. The filter's capture efficiency remains high even when visibly loaded — the accumulated particles actually increase capture efficiency temporarily — but as the filter loads further, airflow resistance increases and CADR drops. The purifier motor works harder to push air through a loaded filter, increasing noise and electricity consumption without improving filtration.

Replacement frequency for Indian homes:

Replace every 6–9 months in high-PM2.5 cities (Delhi, Gurugram, Noida, Lucknow, Kanpur). Replace every 9–12 months in moderate-PM2.5 cities (Mumbai, Pune, Bengaluru, Hyderabad) if the purifier runs 8–10 hours per day. Homes with regular incense burning, active cooking without exhaust fans, or recent renovation should lean toward the shorter end of these intervals.

Signs a filter needs immediate replacement:

The purifier's app or filter indicator shows a replacement alert · Noticeably reduced airflow at the same fan speed · Odour from the purifier (indicates mould or bacterial growth on a damp, loaded filter — more common during monsoon) · PM2.5 readings that do not improve as expected when the purifier is running

Filter replacement cost — what to check before buying:

Replacement filter costs in India range from ₹500–1,500 for basic H10 filters in budget purifiers to ₹1,500–4,000 for certified H11/H12 replacement filters in mid-range devices, and ₹3,000–7,000+ for H13 replacement filters in premium brands. Before purchasing any air purifier, confirm the replacement filter is available in India at a published price. Purifiers with filters only available through single-seller import channels create a long-term cost and availability risk that the upfront unit price does not reflect.

Can you wash a HEPA filter?

No. True HEPA filters (H11 and above) cannot be washed without destroying the filter media. Water disrupts the randomly oriented fibre structure that creates the particle capture matrix — once wet and dried, the fibres clump and the filter is no longer effective. Some purifiers include a washable pre-filter mesh positioned above the HEPA element. This pre-filter can be rinsed every 2–4 weeks to extend HEPA filter life by catching larger particles before they reach the HEPA layer. Never wash the HEPA element itself.

The Karban Airzone H11 HEPA-class filter includes an antimicrobial and antibacterial coating that reduces microbial accumulation on the filter surface between replacement cycles — particularly relevant during Indian monsoon months when humid air passing through a loaded filter can promote mould growth.

Key Takeaways

HEPA is a performance standard, not a brand name — it requires filters to capture particles at 0.3 microns (the most penetrating particle size) at a defined minimum efficiency
EN 1822 grades H10–H12 are HEPA-class; H13–H14 are True HEPA. "HEPA-type" is not a grade and has no minimum regulatory standard
HEPA captures PM2.5, PM10, bacteria, mould spores, and pollen — but does NOT capture VOCs, formaldehyde, or odours. An activated-carbon stage is required for gas-phase pollutants
For Indian homes with new furniture or recent renovation, a multi-stage HEPA + carbon purifier is the complete solution
Filter grade and CADR must both be evaluated — an H11 filter in a powerful motor will outperform an H13 filter in a weak motor in a real room
A minimum CADR of 200 m³/h is required for meaningful air quality improvement in a standard Indian bedroom of 150–200 sq ft
In Indian high-PM2.5 conditions, replace HEPA filters every 6–9 months — not the 12-month cycle calculated for lower global pollution averages
Never wash a HEPA filter — water destroys the fibre capture matrix. Replace, do not clean
BIS certification is the minimum compliance standard to verify for any air purifier sold in India
The Karban Airzone H11 HEPA-class filter includes antimicrobial/antibacterial coating, delivers CADR 250 m³/h from ceiling height, and shows live AQI readings in the app

Experience It

KARBAN Airzone Pure HEPA Air Purifier with Ceiling Tower Fan — H11 HEPA-class filter, CADR 250 m³/h, live AQI monitoring

The KARBAN Airzone Pure HEPA Air Purifier with Ceiling/Standing Tower fan and dimmable colour-changing LED lights is India's first 3-in-1 overhead appliance. It uses an H11 HEPA-class filter with antimicrobial/antibacterial coating, delivering a verified CADR of 250 m³/h from a ceiling-mounted position — distributing filtered air across the full room in the direction the flaps are pointing, rather than cleaning the air only in the immediate vicinity of a floor unit. The built-in AQI sensor displays live air quality readings on the product itself and tracks historical data in the Karban app — so you can see exactly how indoor PM2.5 changes before and after the purifier runs. BIS Certified, manufactured in India, available across 45+ cities. Starts at ₹14,999 (fan + light) or ₹18,999 with the air purifier module.

Shop Airzone → Book a Call →

Frequently Asked Questions

What does HEPA stand for?

HEPA stands for High Efficiency Particulate Air. The term originated in the 1940s in the US when the Atomic Energy Commission needed high-efficiency filtration for nuclear research facilities. Today it refers to a performance standard under EN 1822 (used in India and Europe) that requires a filter to capture a defined minimum percentage of particles at 0.3 microns — the most penetrating particle size and the hardest to filter.

What is the difference between HEPA-class and True HEPA?

HEPA-class filters (H10–H12 under EN 1822) capture 85–99.5% of particles at 0.3 microns. True HEPA (H13–H14) captures 99.95% or above. For residential use, the practical difference depends heavily on CADR — a HEPA-class filter with high air throughput will outperform a True HEPA filter in a weak motor in a real room. H11 HEPA-class is the standard for Indian residential air purifiers with sufficient CADR.

Is a "HEPA-type" filter the same as a rated HEPA filter?

No. "HEPA-type" or "HEPA-style" are marketing terms with no regulatory minimum under EN 1822 or US HEPA standards. A rated HEPA filter carries a specific grade (H10, H11, H12, H13) and has been tested against the EN 1822 standard. If the product does not specify a grade, assume the filter is unrated and its capture efficiency is unknown.

Can you wash or clean a HEPA filter?

No — HEPA filters (H11 and above) cannot be washed without destroying the filter media. Water disrupts the randomly oriented fibre structure that creates the particle capture matrix. Some purifiers include a washable pre-filter mesh above the HEPA element — this can be rinsed every 2–4 weeks to extend HEPA filter life. The HEPA element itself must be replaced, not cleaned. Never attempt to vacuum or tap out a loaded HEPA filter — this dislodges captured particles back into the air.

Does a HEPA filter remove formaldehyde from new furniture?

No. HEPA filters capture particles by physical interception. Formaldehyde is a gas and passes through HEPA filter fibres unaffected. Removing formaldehyde and other VOCs requires an activated-carbon filter stage, which works through chemical adsorption. A complete air purifier for a newly furnished Indian home should include both HEPA and activated carbon stages.

How often does a HEPA filter need to be replaced in Indian conditions?

In Indian urban conditions — PM2.5 above 35 µg/m³ — replace the HEPA filter every 6–9 months rather than the 12-month cycle most manufacturers state. Manufacturers' replacement schedules are calculated against global pollution averages well below Indian metro levels. Homes near construction sites or with regular cooking and incense use should replace closer to every 6 months. The Karban app tracks filter usage and notifies when replacement is due.

Is HEPA filtration safe for babies and young children?

Yes — HEPA filtration is entirely safe and strongly recommended for infants and young children. Children have higher breathing rates relative to body weight and developing lungs that are more vulnerable to PM2.5 exposure. A HEPA air purifier running continuously in a child's bedroom reduces PM2.5, dust mite allergens, mould spores, and bacteria — the core airborne triggers for childhood asthma and allergies in India. H11 HEPA-class filtration is the standard for children's rooms.

Does a higher HEPA grade mean less airflow?

Yes, denser filter media increases air resistance. This is why CADR — not grade alone — is the more meaningful metric. A purifier engineered for H13 filtration must have a motor powerful enough to maintain adequate airflow through the denser filter. Not all products labelled H13 achieve the same real-world CADR. Verify CADR alongside filter grade for every purchase.

Can a HEPA filter remove cooking smoke?

Yes, HEPA filters capture PM2.5 and fine particles from cooking smoke effectively. However, cooking also generates CO, NO2, and acrolein — gases that a HEPA filter cannot capture. Running a purifier with both HEPA and carbon filtration immediately after a cooking episode is the most complete approach. Keeping the kitchen door closed during cooking prevents fumes from reaching the bedroom purifier.

What is the minimum CADR I need for an Indian bedroom?

For a standard Indian bedroom of 150–200 sq ft with a 9–10 ft ceiling (approximately 130–165 m³ of air), a CADR of 200–250 m³/h provides approximately 1.2–1.9 air changes per hour. For 2–3 air changes per hour during high-pollution periods, 250 m³/h or above is recommended. Use the formula: room coverage (sq ft) = 1.5 × CADR to verify any purifier's coverage against your room size.

Does a HEPA filter help with pollen allergies in India?

Yes. Pollen particles (10–100 microns) are well within the capture range of any HEPA-class filter. For allergy sufferers during monsoon season or in cities near green belts, a HEPA purifier running in the bedroom significantly reduces airborne pollen concentration. H11 HEPA-class or above captures pollen with near-complete efficiency.

Should I run a HEPA air purifier continuously or only when needed?

Continuous low-speed operation is more effective than running at high speed only when pollution is noticeable. PM2.5 infiltration into a sealed room is a steady process — the purifier maintains a lower equilibrium concentration by running continuously rather than reacting after concentrations rise. At low speed, a well-engineered purifier draws minimal power (22W for the Karban Airzone at Speed 6) and produces 27 dB — quiet enough for uninterrupted sleep.