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Tag: hepa filter

  • PM2.5 vs PM10: What Is the Difference and Which Matters More Indoors?

    PM10 is particulate matter 10 microns across or smaller; PM2.5 is the finer fraction, 2.5 microns or smaller. PM10 is mostly dust and mostly lodges in the nose and throat, while PM2.5 is mostly smoke and combustion particles and can travel deep into the lungs. Indoors, PM2.5 is the number that matters more, and a HEPA purifier captures both.

    What the Numbers Mean

    “PM” stands for particulate matter: tiny solid or liquid particles floating in air. The number is a size cut-off in microns (a micron is a thousandth of a millimetre).

    • PM10 includes every particle 10 microns or smaller.
    • PM2.5 includes every particle 2.5 microns or smaller.
    • PM1.0 includes every particle 1 micron or smaller.

    These are nested, not separate. All of PM2.5 is also counted inside PM10, and all of PM1.0 is inside PM2.5. So when a monitor shows PM10 higher than PM2.5, that is expected: the PM10 figure includes the fine particles plus the coarser ones between 2.5 and 10 microns. Both are far too small to see individually; a human hair is many times wider than either.

    Where Each Comes From in Indian Cities

    Coarser particles (PM10 side)Fine particles (PM2.5 side)
    Main outdoor sourcesRoad dust, construction and demolition, unpaved ground, wind-blown soilVehicle exhaust, stubble and crop-residue burning, wood and waste burning, industry, firecrackers
    Main indoor sourcesSweeping, dusting, shaking bedding, fans lifting settled dustFrying and tadka, agarbatti and dhoop, mosquito coils, smoking, candles
    How they behaveSettle out of the air relatively quickly; come back up when disturbedStay suspended for a long time; travel far and slip through gaps
    When they peakDry, windy days; near construction; summer dustStill, cold evenings and nights; October to January in north India

    This is why a dusty house in summer and a smoky winter evening feel different. Dust you can often see on surfaces; our guide on why your house gets so dusty covers that side. Winter smog is mostly the fine fraction, which you cannot see settling anywhere.

    Why PM2.5 Does More Harm

    The body’s airways act like a series of filters. Larger particles are mostly caught in the nose and throat and cleared by mucus, sneezing and coughing. The smaller the particle, the further it gets:

    • Coarse particles in PM10 mostly irritate the nose, throat and upper airways. That is the sneezing, itchy throat and dust-allergy side of air pollution.
    • PM2.5 can reach the small airways and air sacs deep in the lungs, where the body’s clearing mechanisms are slower.
    • Fine particles from combustion also tend to carry the products of burning with them, which is part of why smoke is treated as more harmful than plain dust.

    That is why the health limits for PM2.5 are much stricter than for PM10, and why public health agencies focus on PM2.5. If smog season brings on throat burning or watery eyes, see our page on throat irritation and burning eyes in smog; for anything that persists or affects breathing, see a doctor.

    In one line: PM10 is mostly the dust you can sweep; PM2.5 is mostly the smoke you cannot see. Indoors in winter, watch PM2.5 first.

    PM1.0: The Smallest Number on Your Monitor

    Some monitors and purifiers also report PM1.0. It is the finest slice of PM2.5 and is dominated by fresh combustion particles: vehicle exhaust, burning, incense and cooking smoke. There is no Indian standard for PM1.0, so it is best used as a trend signal. If PM1.0 jumps while you are cooking or lighting dhoop, the source is in the room; if it climbs slowly in the evening with the windows shut, it is likely seeping in from outside.

    What Each Kind of Sensor Can See

    Most home air-quality monitors and purifier sensors use a laser particle sensor. A small fan draws air past a laser beam, the sensor counts the flashes of scattered light, and software estimates the mass in each size range.

    • Laser particle sensors report PM1.0, PM2.5 and PM10. They measure particle size, not what the particle is. They cannot tell pollen from smoke from dust.
    • Gas sensors (TVOC, eCO₂, NO₂) measure different things altogether: volatile chemicals, an estimate of carbon dioxide build-up, and a traffic-related gas. They do not see particles.
    • Older or very cheap “dust” sensors often report a single vague number and struggle with the finest particles. A monitor that shows only one unlabelled number is not telling you much.

    For a full comparison of monitors, apps and what each can measure, read how to check air quality at home.

    Boon Airvana’s AtmoScan sensor reads PM1.0, PM2.5 and PM10 with a laser, plus TVOC, eCO₂ and NO₂, every second, so you can see which kind of pollution is in your room.

    See Boon Airvana →

    How a HEPA Purifier Handles Both

    A HEPA filter is a dense mat of fine fibres. It does not work like a sieve with holes of a fixed size; particles are caught by several mechanisms at once. Large particles slam into fibres, mid-sized ones are intercepted as they pass close to a fibre, and the very smallest ones zig-zag randomly and stick when they touch a fibre. There is a size in between, around 0.3 microns, that is hardest to catch, and HEPA filters are rated at that hardest size.

    • PM10: the pre-filter catches the largest dust and hair; the HEPA layer catches the rest of the coarse fraction easily.
    • PM2.5 and PM1.0: captured by the HEPA layer. An H13 grade filter captures 99.95% of particles in a single pass at its rated test size.
    • Gases and smells: not captured by HEPA at all. That is the job of an activated carbon layer, and even carbon only helps with some gases. Our guide on HEPA vs ionizer vs UV purifiers explains why HEPA is the technology to rely on for particles.

    The filter grade is only half the story. How much air passes through the filter each hour (the CADR) decides how quickly the room’s particle level actually falls.

    Indian Limits and Which Number to Watch

    StandardPM2.5PM10
    India NAAQS, 24-hour60 µg/m³100 µg/m³
    India NAAQS, annual40 µg/m³60 µg/m³
    WHO 2021 guideline, 24-hour15 µg/m³Not covered here
    WHO 2021 guideline, annual5 µg/m³Not covered here

    For daily decisions in an Indian home: in winter, watch PM2.5 and keep it under 60 µg/m³ at the very least, as close to 15 as you can manage in the bedroom. In dusty months, PM10 tells you when to close up and when the sweeping has stirred things up. PM1.0 tells you when something in the room is burning.

    Frequently Asked Questions

    What is the difference between PM2.5 and PM10?

    PM10 is all particulate matter 10 microns or smaller; PM2.5 is the finer part, 2.5 microns or smaller. PM2.5 is counted inside PM10. PM10 in Indian cities is dominated by road dust and construction, while PM2.5 comes mostly from combustion: vehicles, stubble and waste burning, firecrackers, and indoor smoke from cooking and incense.

    Which is more harmful, PM2.5 or PM10?

    PM2.5 is generally considered more harmful because the particles are small enough to reach deep into the lungs, where they are cleared more slowly. Coarser PM10 particles are mostly trapped in the nose and throat. That is why PM2.5 limits are much stricter. Both are worth reducing, but indoors in winter PM2.5 is the number to watch first.

    Why is my PM10 reading always higher than PM2.5?

    Because PM10 includes PM2.5. The PM10 figure counts all the fine particles plus the coarser ones between 2.5 and 10 microns, so it is always equal to or higher than PM2.5. A big gap between the two means a lot of coarse dust; readings close together mean the air is mostly fine particles, typical of smoke and winter smog.

    Does a HEPA air purifier remove both PM2.5 and PM10?

    Yes. A HEPA filter captures both coarse and fine particles, and an H13 grade filter captures 99.95% of particles in a single pass at its rated size. How quickly the room clears depends on the purifier’s CADR relative to the room size and on keeping the door closed. HEPA does not capture gases or odours.

    What is PM1.0 and should I worry about it?

    PM1.0 is particles 1 micron or smaller, the finest part of PM2.5. It mostly comes from fresh combustion such as vehicle exhaust, incense and cooking smoke. India has no separate standard for it, so treat it as a signal: a sudden PM1.0 spike usually means something is burning in or near the room.

    Can an air quality sensor tell if particles are pollen or smoke?

    No. Laser particle sensors measure particle size and estimate mass in each size range; they cannot identify what a particle is made of. You can make reasonable guesses from patterns, for example a PM1.0 spike while cooking, but a home sensor cannot confirm pollen, mould spores or smoke specifically.

    See PM1.0, PM2.5 and PM10 in your room separately, every second. Boon Airvana pairs a laser particle sensor with an H13 HEPA filter.

    See Boon Airvana →

  • H13 vs H14 HEPA Filter: Which Grade Do Indian Homes Need?

    For a home air purifier, H13 HEPA is enough. H13 captures at least 99.95% of particles at their most penetrating size, and H14 captures at least 99.995%. That gap is real in a hospital cleanroom, but in a living room the purifier’s CADR, the filter’s seal and how closed your room is make a far bigger difference to the air you breathe.

    HEPA Grades Under EN 1822

    Most HEPA grades on purifier boxes come from the European standard EN 1822. It tests filters at the Most Penetrating Particle Size (MPPS), the particle size that slips through a given filter most easily, typically somewhere around 0.1 to 0.3 microns. Larger and smaller particles are both caught more easily than the MPPS, so the rating is a worst case.

    ClassGroupMinimum efficiency at MPPSParticles let through, per 10,000
    E10EPA85%Up to 1,500
    E11EPA95%Up to 500
    E12EPA99.5%Up to 50
    H13HEPA99.95%Up to 5
    H14HEPA99.995%Up to 0.5

    Classes E10 to E12 are EPA (Efficient Particulate Air) filters, not HEPA. Only H13 and H14 are HEPA under the current standard. Grades above H14 (the U classes) are for cleanrooms and are not relevant to homes.

    True HEPA vs HEPA-Type

    True HEPA is a marketing phrase, not a grade, but it usually signals a filter tested to a HEPA standard. The phrase is common on products built to a US definition of HEPA, which specifies 99.97% capture at 0.3 microns. In practice, a filter labelled H13 under EN 1822 tells you more, because it names the standard and the class.

    HEPA-type, HEPA-like or HEPA-style means the media looks similar but is not graded to a HEPA standard. It may capture far fewer fine particles. Treat it as a red flag.

    The H11 and H12 caveat. An older version of EN 1822 used H10, H11 and H12 for what are now E10, E11 and E12. Some listings still use the old names, so “H12 HEPA” today is, in the current standard’s terms, an E12 EPA filter. That is not necessarily bad, but it is not the same as H13, and the name can make it sound closer than it is. For how HEPA compares with ionisers and UV, see HEPA vs ioniser vs UV comparison.

    H13 vs H14: The Real Difference

    On paper, H14 lets through one-tenth as many MPPS particles as H13. In a single pass, H13 lets through up to 5 in every 10,000; H14 up to 0.5. Both are excellent.

    Inside a home, air passes through the purifier again and again. At four or five air changes an hour, room air is filtered many times over, so the tiny per-pass difference between H13 and H14 shrinks further in the air you actually breathe. Meanwhile H14 media is denser, which can mean more resistance to airflow. Unless the fan is designed for it, a denser filter can deliver less clean air per hour, or need more fan power and noise to deliver the same.

    The practical ranking for a home purifier: enough CADR for the room, then a well-sealed filter, then the HEPA grade. H13 in a correctly sized, sealed purifier beats H14 in an undersized or leaky one.

    Why CADR and Seal Matter More

    CADR measures the clean air a purifier actually delivers, combining airflow and filter efficiency. A purifier with too little airflow for the room will clean it slowly, whatever its grade. Work out what your room needs with the air purifier size calculator, and read the air purifier size guide for the method.

    Seal and bypass. If even a small share of air leaks around the edge of the filter, it is not filtered at all, and that leak can matter far more than the difference between 99.95% and 99.995%. Look for a filter that seats firmly against a gasket. Replace it with the correct filter for the model, because a loose third-party filter can undo a good machine.

    Find the CADR your room needs before you compare filter grades.

    Size Your Room →

    Is H13 Enough for North Indian Winters?

    Yes, for homes. In Delhi-NCR and much of the Indo-Gangetic plain, winter PM2.5 often sits far above India’s NAAQS 24-hour limit of 60 µg/m³ and the WHO 24-hour guideline of 15 µg/m³, with AQI regularly in the Poor to Severe bands. The challenge in those months is volume: outdoor air keeps leaking in, and the purifier must clean faster than it arrives. That is a job for CADR and a closed room, not a higher filter grade.

    What helps most on bad days: size for four to five air changes an hour, keep doors and windows shut while the purifier runs, clean the pre-filter more often, and replace the HEPA filter when the purifier says it is due. If anyone at home has persistent breathlessness, chest tightness or a worsening cough during smog season, see a doctor; a purifier reduces exposure but does not treat illness.

    Where Activated Carbon Fits

    HEPA catches particles, not gases. Cooking fumes, smells and some volatile organic compounds pass straight through it. That is the job of activated carbon, which adsorbs odours and some gases. It is not a fix for every gas: no home purifier removes carbon monoxide, and a purifier does not add oxygen. Our guide on what air purifiers cannot remove covers those limits. Carbon also fills up over time, so the filter change reminder matters for it as much as for the HEPA layer; see air purifier maintenance and filter care.

    Boon Airvana uses an H13 HEPA filter (99.95% of particles in a single pass) with a washable pre-filter, activated carbon and an anti-bacterial coating, in a dual-suction design that draws air through two filters. Its CADR is 380 m³/h, and it reminds you when the filter is due based on the air it has cleaned. It is ₹14,900 at the time of writing.

    Frequently Asked Questions

    Is H14 better than H13 for a home air purifier?

    H14 captures more particles per pass, at least 99.995% against 99.95% at the most penetrating particle size. In a home, though, air passes through the purifier many times an hour, so the difference in the air you breathe is small. CADR, a good filter seal and a closed room matter more. H13 is enough for homes.

    What does H13 HEPA mean?

    H13 is a filter class under the European standard EN 1822. An H13 filter captures at least 99.95% of particles at the most penetrating particle size, the size that gets through most easily, typically around 0.1 to 0.3 microns. It is a common HEPA grade in well-built home air purifiers.

    Is H12 HEPA as good as H13?

    Not quite. Under the current version of EN 1822, the class once called H12 is named E12 and grouped as EPA, not HEPA, with at least 99.5% capture against 99.95% for H13. That is still effective filtration, but if a listing calls an H12 filter HEPA, it is using an older name. Compare CADR as well as grade.

    What is the difference between true HEPA and HEPA-type?

    True HEPA usually means a filter tested to a HEPA standard. HEPA-type or HEPA-like means the media resembles HEPA but is not graded to any HEPA standard, and it may capture far fewer fine particles such as PM2.5. Look for a named grade like H13 rather than descriptive phrases.

    Is H13 HEPA enough for Delhi pollution?

    Yes, for homes. During Delhi winters the challenge is the amount of polluted air leaking in, not the filter grade. Choose a purifier with enough CADR for four to five air changes an hour, keep the room closed while it runs, clean the pre-filter regularly and change the filter when it is due.

    Does a HEPA filter remove gases and smells?

    No. HEPA captures particles, not gases. Odours, cooking fumes and some volatile organic compounds need an activated carbon layer, which adsorbs them until it fills up. Even carbon does not remove every gas. No home purifier removes carbon monoxide, and purifiers do not add oxygen to a room.

    Boon Airvana pairs an H13 HEPA filter and activated carbon with a 380 m³/h CADR. ₹14,900 at the time of writing.

    See Boon Airvana →