They Do Different Jobs

The comparison gets framed as a choice, and it is not really one. A chimney and an air
purifier operate at different points in the same process, and understanding which point is the
whole answer.

• A chimney captures at the source — it removes emissions at the hob, before
  they mix into the room.
• An air purifier filters after dispersal — it cleans what has already
  spread through the space.

In air quality generally, source control beats dilution and filtration, consistently. It is
the reason extraction wins this comparison for cooking, and the reason a purifier is still worth
having for what escapes.

What a Chimney Does

A chimney sits directly above the hob and draws rising hot air, grease aerosol and
particulate into a hood before they disperse. A ducted model then expels it from the
building.

What it handles well:

• Grease aerosol from frying — which no air purifier should be asked to deal with, and which
  otherwise settles as the sticky film that makes everything else in the kitchen adhere
• The particulate spike from tempering and deep-frying, at the moment it is produced
• Heat and humidity, which a purifier does nothing about
• Combustion products from the gas flame itself

Where it falls short: it only captures what rises into the hood. Cooking on a
back burner, or on a hob wider than the hood, leaks. And a ductless model returns filtered air to
the same room, keeping heat and humidity and a share of the particulate indoors.

What an Air Purifier Does

A purifier draws room air through a filter and returns it. For cooking specifically, it is
working at a disadvantage in three ways.

• It is downstream. Particulate has already dispersed before it reaches the
  filter.
• It cannot keep up. High-heat Indian cooking generates particulate faster
  than a domestic unit clears a room.
• Grease is bad for it. Oil aerosol clogs a HEPA filter quickly. Running one
  in an active kitchen shortens filter life sharply.

Where it earns its place is the adjoining space — the living area of an open-plan
flat, or the bedrooms beyond — handling the fraction that escaped the hood.

Side-by-Side

The Open-Plan Complication

Open-plan kitchens are increasingly common in Indian apartments, and they change this
calculation more than anything else on this page.

A closed kitchen contains its own emissions — shut the door and the rest of the home is
largely protected. An open plan removes that boundary. Whatever escapes the hood is now in the
living room, and on its way to the bedrooms.

Two consequences follow:

• The chimney matters more, not less. It is the only containment left.
• A purifier in the living area becomes genuinely useful, because there is
  now a shared volume for it to work on.

If You Can Only Do One

Get the chimney. If your cooking is the sort described anywhere on this page
— tadka, deep-frying, roti on an open flame — source extraction is the higher-value purchase,
and it is not close.

Buy an air purifier first only if your primary concern is not cooking: outdoor
pollution infiltrating during a bad season, allergies, dust, or pets. Those are the problems a
purifier is actually built for.

And if you already have a chimney, the highest-return action costs nothing:
use it every time, switch it on before the oil goes in, and leave it running ten to
fifteen minutes after you finish. Most kitchens with an adequate chimney have a usage
problem rather than an equipment problem.

Where Chimneys Fail

• Undersized hood. A hood narrower than the hob cannot capture the outer
  burners. It should be at least as wide as the cooking surface.
• Long or convoluted ducting. Every bend and metre of duct reduces
  extraction. Short and straight beats powerful and throttled.
• Clogged baffle filters. Grease-saturated filters drastically cut airflow.
  This is the chimney equivalent of never changing a water filter, and it is the most common
  fault by far.
• Mounted too high. Too far above the hob and the plume disperses before it
  is captured. Follow the manufacturer’s height.
• Switched on late, off early. The fix is free and it is the most common
  problem of all.

Frequently Asked Questions

Is a kitchen chimney better than an air purifier?

For cooking emissions, yes, and it is not close. A chimney captures particulate and grease at the hob before they disperse into the room. An air purifier can only filter what has already spread through the space. Extraction at source always beats filtration after dispersal.

Can an air purifier replace a kitchen chimney?

No. It has no way to capture emissions at the point of release, it does nothing about grease deposition on your kitchen surfaces, and it will be overwhelmed by the rate at which high-heat Indian cooking generates particulate. It is a useful complement in an adjoining room, not a substitute.

Do I need an air purifier if I have a good chimney?

In a closed kitchen with a well-sized, well-ducted chimney used consistently, often not for cooking specifically. In an open-plan home the case is stronger, because even a good chimney lets some fraction escape into shared living space — and a purifier there handles what got past.

How long does cooking smoke stay in the air?

Visible smoke clears in minutes, but fine particulate can remain elevated for an hour or more in a poorly ventilated kitchen. This is why the extractor should keep running after cooking finishes rather than being switched off with the hob — the longest-lived fraction is the part still in the room when most people turn it off.

Is a ductless chimney as good as a ducted one?

Generally not. A ducted chimney removes the air from the building. A ductless model filters it through charcoal and returns it to the kitchen, which handles some odour but leaves heat, humidity and a share of the particulate in the room. Where ducting is possible, it is the better option.

Why Purifiers Add Things Back in the First Place

Reverse osmosis works by forcing water through a membrane fine enough to block dissolved
substances. That is what makes it the only household technology capable of removing heavy
metals, nitrate, fluoride and high TDS — and it is also why RO cannot be selective. The
membrane does not distinguish between arsenic and calcium. Both are dissolved; both are
rejected.

So RO water arrives almost entirely demineralised. Two consequences follow, one real and one
frequently overstated:

• Taste changes, noticeably. Dissolved minerals are much of what makes
  water taste like water. Fully demineralised water tastes flat.
• A small dietary contribution is lost. Drinking water contributes some
  calcium and magnesium — but for anyone eating a reasonable diet it is a minor source, not a
  primary one. This is worth restoring; it is not worth panicking about.

Every Indian brand now answers this with a post-RO stage, and they have converged on three
approaches — mineral, alkaline, and copper. They are marketed almost interchangeably. They are
not the same thing, and they are not equally well supported.

Mineral Cartridges — The One With the Clearest Rationale

What it does

A mineral cartridge reintroduces calcium and magnesium — usually from mineral-bearing media
that dissolve slowly into the passing water. The purpose is straightforward: put back
approximately what the membrane took out.

Why the logic holds

This is the only one of the three whose stated purpose matches what it demonstrably does.
RO removes calcium and magnesium; a mineral cartridge adds calcium and magnesium. Taste
improves audibly — most people can tell the difference in a blind comparison, which is not
something you can say for the other two.

Expect output TDS to rise by a modest amount, often a few tens of ppm. That is the cartridge
working, not a fault.

What to check

• It is a consumable. The media dissolves; it is used up. A mineral stage
  that has never been replaced stopped contributing a long time ago.
• Ask what is being added. Calcium and magnesium have a rationale. Vague
  “essential minerals” language often means nobody wants to be specific.

Alkaline — Where the Claims Outrun the Evidence

What it does

An alkaline stage raises the pH of the water, typically into the 8–9.5 range, either by
adding alkaline minerals or through an ionisation process. That much is real and measurable.

What is claimed, and what stands up

The marketing claims are large: that alkaline water neutralises acidity in the body,
improves metabolism, slows ageing, boosts immunity. These do not hold up well.

The reason is basic physiology. Stomach acid sits around pH 1.5–3.5 — strongly acidic by
design. Water at pH 9 entering that environment is neutralised almost immediately. Beyond the
stomach, blood pH is held within a very narrow range by the kidneys and respiratory system
regardless of diet. The idea that a glass of water shifts systemic pH is not how the body
works.

There is some limited research worth acknowledging honestly — a few studies on alkaline
water and reflux symptoms, and some on hydration markers after intense exercise. That research
is narrow, and it does not support the general wellness claims printed on boxes.

Copper — Tradition, Some Science, and a Dose Question

What it does

A copper stage introduces a controlled quantity of copper into the purified water, echoing
the traditional practice of storing drinking water in copper vessels — tamra jal in
Ayurvedic practice.

The part that is genuinely supported

Copper has real antimicrobial properties. This is well documented: copper surfaces
inactivate a range of bacteria on contact, which is why copper alloys are used for high-touch
surfaces in some hospital settings. Studies on water stored in copper vessels have found
reductions in bacterial contamination.

The part that is usually left out

Those studies mostly examine water that was contaminated to begin with — the
traditional context, where copper storage was doing meaningful public-health work. In a modern
purifier, the copper stage sits after the RO membrane and UV lamp. The
bacteria are already gone. Copper’s best-evidenced benefit is largely spent on a problem that
has already been solved upstream.

Copper is also an essential trace nutrient, and small dietary amounts are beneficial. But it
has defined limits in Indian drinking water standards for good reason, so the engineering
question is whether the cartridge delivers a controlled dose or an unpredictable one.
A reputable system will specify this. And anyone with Wilson’s disease or another
copper-metabolism disorder should avoid copper-enriched water entirely and follow medical
advice.

Side-by-Side Comparison

The Detail Almost Nobody Checks: Order

This matters more than which cartridge you pick, and it is almost never discussed.

If minerals are introduced before the RO membrane, the membrane removes
them again — and in the process the added mineral load contributes to membrane fouling and
shortens its life. The stage has to sit after full RO to do anything at
all.

Some systems also blend a portion of unpurified water back into the output to raise TDS and
restore taste — sometimes called a TDS controller or a blend valve. It is cheaper than a
mineral cartridge, and it works for taste. But it is important to understand what it is doing:
the bypassed water carries everything the membrane was installed to remove. On
a genuinely contaminated supply, that is a meaningful compromise, and it is rarely explained at
the point of sale.

Which One Do You Need?

Four Mistakes Buyers Make

• Treating these stages as purification. They are not. The membrane does
  the purifying; these change what the clean water tastes like.
• Paying a large premium for alkaline health claims. The evidence does not
  support them.
• Not asking whether TDS is restored by minerals or by blending. Same
  meter reading, entirely different water.
• Never replacing the cartridge. All three are consumables. An unreplaced
  mineral stage is an empty tube the water passes through.

Frequently Asked Questions

Which is better — alkaline, copper, or mineral water purifier?

A mineral cartridge has the clearest rationale of the three: RO removes calcium and magnesium, and a mineral stage puts them back, which improves taste and restores a small dietary contribution. Alkaline stages raise pH, but the health claims made for high-pH water are not well supported. Copper is rooted in traditional practice and copper does have genuine antimicrobial properties, though in already-purified water there is little left to act on. If you are choosing one, choose mineral.

Does RO water need minerals added back?

RO removes most dissolved minerals along with the contaminants — that is inherent to how the membrane works. Drinking water is not most people’s main source of calcium and magnesium, so the nutritional impact is modest for anyone eating a reasonable diet. The more noticeable effect is taste: fully demineralised water tastes flat. A mineral stage addresses both, which is why most Indian RO purifiers now include one.

Is alkaline water actually good for you?

The strong claims — that it neutralises body acidity, slows ageing, or prevents disease — are not supported by good evidence. Your stomach is strongly acidic and your body regulates blood pH within a narrow range regardless of what you drink. There is some limited research on alkaline water for reflux symptoms and on hydration after exercise, but it does not support the general health claims made in marketing. Alkaline water is not harmful; it is just oversold.

Is a copper water purifier safe?

In a properly designed purifier, yes. Copper is an essential trace nutrient and small amounts are fine. The thing to check is that the system controls the dose — copper has defined limits in Indian drinking water standards, and a well-engineered cartridge releases a controlled quantity rather than an unpredictable one. Anyone with Wilson’s disease or another copper-metabolism disorder should avoid copper-enriched water and follow medical advice.

Do mineral cartridges increase TDS?

Yes, slightly and deliberately. A mineral stage adds dissolved calcium and magnesium back, so post-filter TDS rises — commonly by a few tens of ppm. This is not contamination and it is not a fault. If you measure your purifier’s output with a TDS meter and it reads higher than you expected, a mineral or alkaline stage is usually the explanation.

Why the Technology Choice Matters More Than the Brand

Air purifier boxes in India list technologies the way restaurant menus list ingredients —
HEPA, activated carbon, UV, ioniser, plasma, “negative ions” — as though more
entries mean a better product. They do not. Each of these does something quite specific, two of
them do most of the work, and two are frequently there to lengthen the list.

The useful way to think about it: air pollution indoors comes in two forms,
and they need different answers.

• Particles — PM2.5, PM10, dust, pollen, smoke, pet dander. Physical
  matter suspended in air. This is what HEPA is for.
• Gases — VOCs, cooking odours, vehicle exhaust, formaldehyde from new
  furniture. Molecules, far smaller than any filter’s pores. This is what carbon is for.

HEPA — The One That Does the Work

How it works

A HEPA filter is a dense mat of randomly arranged fibres. Air passes through; particles do
not, because they are intercepted, they collide with fibres, or — for the very smallest — they
drift into fibres through Brownian motion. It is worth knowing that HEPA is not a sieve with
0.3-micron holes. That size is simply the hardest to catch, which is why the standard
is measured there. Particles both larger and smaller are captured more efficiently.

What HEPA removes

• PM2.5 and PM10: the fine particulate that drives most of India’s air
  quality concern.
• Pollen and dust mite debris: the common indoor allergens.
• Smoke particles: from cooking, traffic, and crop burning.
• Pet dander: and the airborne fraction of pet hair.
• Particle-borne microorganisms: bacteria and virus-carrying droplets are
  within the captured size range.

What HEPA cannot do

• Nothing for gases or odours. Molecules pass straight through. A room can
  be at zero PM2.5 and still smell of last night’s cooking.
• It saturates. Efficiency holds up as it loads, but airflow falls — and
  falling airflow means falling clean-air delivery. A neglected filter is a slow strangulation
  of the machine.
• It needs a fan behind it. A superb filter with a weak fan produces a
  poor purifier, because what protects a room is volume of clean air per hour, not
  filter grade.

Activated Carbon — For Everything HEPA Misses

How it works

Activated carbon is processed to be extraordinarily porous — a small mass carries an
enormous internal surface area. Gas molecules adhere to that surface as air passes through, a
process called adsorption. It is genuinely the only practical domestic answer to odours and
VOCs.

The catch, and it is a big one

Carbon works by filling up, and once its surface is occupied it stops. Worse, a saturated
carbon filter can release some of what it held when conditions change. So the question is never
whether a unit has carbon — nearly all claim to — but how much.

A carbon-impregnated fabric sheet wrapped around a HEPA filter contains a few grams. It will
handle odours for a few weeks and then be inert. A genuine carbon stage is a granular bed
weighing several hundred grams or more, and manufacturers that have invested in one will state
the weight. Silence on that number tells you what you need to know.

UV — Mostly Marketing in a Domestic Air Purifier

This deserves a careful answer, because UV is genuinely effective in other contexts — and
that is exactly why it sells here.

Ultraviolet light at germicidal wavelengths damages microbial DNA and prevents reproduction.
The dose required is a product of intensity and exposure time. That is the
problem. In a water purifier, water flows slowly through a chamber built around the lamp, and
contact time is sufficient — which is why
UV genuinely
earns its place in water purification. In an air purifier moving a few hundred cubic metres
an hour, each parcel of air is past the lamp in a fraction of a second.

There are engineered UV air systems that work — in hospitals, using high-output lamps,
long ducted exposure paths, and upper-room configurations. A small lamp tucked beside the fan
of a domestic unit is not that. Meanwhile the HEPA filter in the same machine is already
capturing those organisms physically.

Ionisers and Ozone — Why We’d Skip Them

An ioniser emits charged ions that attach to airborne particles. The particles acquire a
charge, clump together, become heavier, and fall out of the air onto floors, walls and
furniture.

Read that again, because it is the whole issue: the particles have not been removed
from the room. They have been moved from the air to your surfaces. An air quality
sensor will report improvement, because the sensor measures air. Disturb the room — walk
across it, sit down on the sofa — and a fraction of it returns to the air.

The more serious concern is ozone. Some ionisers generate it as a
by-product, and a category of devices sold as “ozone generators” or
“activated oxygen” purifiers produce it deliberately. Ozone is a respiratory
irritant. Generating it in an occupied room trades a particle problem for a gas problem, and
the trade is a bad one — particularly for the asthma and allergy sufferers most likely to be
buying a purifier in the first place.

Side-by-Side Comparison

What a Good Stack Actually Looks Like

Three stages, in this order, and the order is not arbitrary:

1. Washable pre-filter. Catches hair and coarse dust so they never reach
   the HEPA. This is what makes the expensive filter last, and washing it monthly is the single
   cheapest thing you can do for running costs.
2. True HEPA, H13 or better. The particulate removal. Everything else is
   supporting cast.
3. Substantial activated carbon. Sized in hundreds of grams, not printed on
   a sheet — assuming odours or VOCs are part of your problem.

Behind all three, a fan capable of delivering a CADR that suits your room. A specification
sheet that lists five technologies but no CADR figure is describing a product that would rather
you did not compare it.

Five Mistakes Buyers Make

• Counting stages instead of reading them. A seven-stage purifier with a
  weak fan is worse than a three-stage unit with a strong one.
• Buying filter grade and ignoring CADR. H14 behind an underpowered fan
  protects less room than H13 behind a good one.
• Assuming carbon is carbon. A few grams on a sheet and a proper granular
  bed differ by an order of magnitude and are described with the same word.
• Paying for UV in an airstream. Almost no contact time; the HEPA is
  already handling it.
• Treating an ioniser as purification. It relocates particles rather than
  removing them, and may add ozone in the process.

Frequently Asked Questions

Is HEPA or ionizer better for an air purifier?

HEPA, without much argument. A HEPA filter physically traps particles and removes them from the room when you change the filter. An ioniser charges particles so they clump and settle onto your floor and furniture — the air sensor reads cleaner because the particles left the air, not because they left the room. HEPA is removal; ionisation is relocation.

Does a UV air purifier actually kill germs?

UV kills microorganisms given enough intensity and enough exposure time. Inside a domestic air purifier, air moves past the lamp in a fraction of a second, which is usually far too little contact time for meaningful inactivation. UV works well in water purifiers, where flow is slow and the path is engineered around the lamp. In a fast-moving airstream it is mostly a label.

Do I need activated carbon in an air purifier?

If odours, cooking fumes, traffic exhaust or VOCs are part of your problem, yes — HEPA does nothing for gases. But check the quantity. A thin carbon-impregnated sheet saturates within months and then does nothing. A genuine carbon bed is measured in hundreds of grams or more, and the specification will usually say so.

Are ozone air purifiers safe to use at home?

No. Ozone is a respiratory irritant, and devices that deliberately generate it should not be run in occupied rooms. Some ionisers also produce ozone as a by-product. If a product markets ozone or ‘activated oxygen’ as a feature, treat that as a reason to avoid it rather than a selling point.

What does H13 mean on an air purifier filter?

H13 is a grade under the EN 1822 standard, requiring the filter to capture at least 99.95% of particles at the most-penetrating particle size, around 0.3 microns. H14 is stricter at 99.995%. The important contrast is with ‘HEPA-type’ or ‘HEPA-style’, which are not graded at all and are not held to the standard.