★ SOSA reed diffusers · windows and sills
A window stacks sun, heat and moving air in one place, which is why the prettiest position in the room is also the most expensive
★ ★ ★ ★ ★
★★★★★
"The sill looked perfect and cost me three weeks. It now lives on the console opposite and behaves completely differently."
Garden Bloom 50ml
★★★★★
"I thought near the window meant the scent would travel through the house. It travelled out of the house instead."
Fresh Brew 50ml
★★★★★
"Balcony door in Mumbai, monsoon breeze all day. The reeds looked dry at the top and the level fell fast. Moved it inward, sorted."
Mountain Breeze 130ml
★★★★★
"Two feet inward onto a wooden shelf was the entire fix. I had assumed I needed a stronger fragrance."
Morning Freshness 50ml
★★★★★
"Kitchen window over the sink seemed sensible until I read why cooking and fragrance should never overlap."
Kitchen placement
★★★★★
"Dust from the road was collecting on the reeds. Never occurred to me that an open window brings that in too."
Evening Calm · reeds
★★★★★
"The sill looked perfect and cost me three weeks. It now lives on the console opposite and behaves completely differently."
Garden Bloom 50ml
★★★★★
"I thought near the window meant the scent would travel through the house. It travelled out of the house instead."
Fresh Brew 50ml
★★★★★
"Balcony door in Mumbai, monsoon breeze all day. The reeds looked dry at the top and the level fell fast. Moved it inward, sorted."
Mountain Breeze 130ml
★★★★★
"Two feet inward onto a wooden shelf was the entire fix. I had assumed I needed a stronger fragrance."
Morning Freshness 50ml
★★★★★
"Kitchen window over the sink seemed sensible until I read why cooking and fragrance should never overlap."
Kitchen placement
★★★★★
"Dust from the road was collecting on the reeds. Never occurred to me that an open window brings that in too."
Evening Calm · reeds
✓ Keep out of direct sunlight · stand the bottle on a tray · flip weekly with gloves ✓ Six fibre reeds per bottle · tested through 45°C heat and 85% monsoon humidity ✓ 50ml lasts 6–8 weeks · 130ml lasts 14–18 weeks · free shipping above ₹499
Founder Diaries · Reed Diffusers · Placement
The three: direct sunlight heating the glass and the oil inside; a sill or ledge that stores and re-radiates heat; and air exchange with outside, which strips the reeds and carries fragrance out of the room.
How much? Our working guidance is that a sunlit, ventilated sill can take a 50ml well below its stated 6–8 weeks — a third to a half in a hot month. Treat that as a range from testing and customer reports, not a measurement.
The fix: move it two feet inward, out of the beam, onto a console or shelf at waist to chest height near a doorway. Free, and the room usually smells better afterwards, not worse.
Fresh Brew₹849 · 9.5/10Indian window ledges are usually stone, tile or granite, sometimes with a metal frame, and all of those store heat well. They take in sun through the middle of the day and give it back through the evening, so a bottle can be in complete shade at seven o'clock and still standing on something distinctly warm. This is the accelerant that survives your fix if the fix is only a curtain. Drawing a sheer curtain removes the beam but leaves the ledge warm, which is why the honest advice is distance rather than shading — off the sill entirely, onto a wooden or ceramic surface further into the room. It also solves a second problem: reed oil marks stone and wood, and a sill is a difficult place to keep a tray.
Garden Bloom · entrywaysfrom ₹799Shop → 
Fresh Brew · living roomsfrom ₹849Shop → 
Fresh & Grounded duo · 2 × 50ml₹1,548Shop →
SOSA reed diffuser range & prices (verified August 2026): alcohol-free, phthalate-free, paraben-free and IFRA-compliant compositions on a heat-stable coconut-derived (CCT) carrier, low-VOC, supplied in a refillable glass bottle with six fibre reeds; 50ml lasts 6–8 weeks and 130ml lasts 14–18 weeks. Morning Freshness (Malabar lemon · peppermint · Nilgiri eucalyptus) 50ml ₹749 · 130ml ₹1,249 · 9.0/10; Garden Bloom (British rose · night-blooming jasmine) 50ml ₹799 · 130ml ₹1,299 · 8.9/10; Evening Calm (Kashmir lavender · chamomile) 50ml ₹799 · 130ml ₹1,299 · 8.9/10; Fresh Brew (Coorg coffee · Kerala vanilla) 50ml ₹849 · 130ml ₹1,349 · 9.5/10; Mountain Breeze (Himalayan pine · sage · Indian cedar) 50ml ₹849 · 130ml ₹1,349 · 9.4/10. Reed diffuser refills are oil only — you reuse your own vessel and reeds: 300ml ₹2,399 (roughly 8–11 months) · 500ml ₹3,499 (roughly 14–18 months), about ₹7–8 per ml against ₹15–17 per ml for a 50ml bottle. Duo sets ₹1,498–₹1,598 for 2 × 50ml and ₹2,498–₹2,598 for 2 × 130ml. Strength figures are positions on SOSA’s own internal strength scale, not an industry standard. Replacement reeds are not sold as a separate SKU; SOSA guidance is to refresh reeds every few months. The reed line is separate from the water-based Hotel Collection for ultrasonic machines (15ml ₹299 · 100ml ₹999 · 300ml ₹1,799) and the two are not interchangeable. Diffusers: Boond 300ml ₹899 · Sukoon 500ml ₹1,899 · Megh 6L ₹3,499 · waterless Vaayu ₹11,999. Composed and handmade in small batches in Pune, India; tested through 45°C summer heat and 85% monsoon humidity. Free shipping above ₹499. A portion of every order supports girl-child education through Nanhi Kali. Prices subject to change — see the live product pages.
Yes — and more than that, a window is usually the single worst place in a home to stand a reed diffuser. Not because of one thing, but because of three arriving together in a spot that looks made for it. Sun on the glass, a sill that stores heat, and outdoor air moving across the reeds: every accelerant we write about, stacked in one location. The photograph of a diffuser on a windowsill in morning light is the most misleading image in this category, and correcting it costs nothing at all — the better position is usually two feet away.
Quick answers — read this first
Does a window shorten a reed diffuser? Yes, and typically by more than any other placement error, because it combines three separate accelerants rather than one.The three: direct sunlight heating the glass and the oil inside; a sill or ledge that stores and re-radiates heat; and air exchange with outside, which strips the reeds and carries fragrance out of the room.
How much? Our working guidance is that a sunlit, ventilated sill can take a 50ml well below its stated 6–8 weeks — a third to a half in a hot month. Treat that as a range from testing and customer reports, not a measurement.
The fix: move it two feet inward, out of the beam, onto a console or shelf at waist to chest height near a doorway. Free, and the room usually smells better afterwards, not worse.
The short answer
Short answer: a window is where sun, heat and moving air meet. Sunlight warms the bottle far above room temperature, which thins the oil and raises evaporation; the sill itself — stone, tile or a metal-framed ledge — stores that heat and gives it back for hours; and any opening to outside, even a gap, moves air across the exposed reed ends and carries the fragrance out rather than into the room. Each of those alone shortens a bottle. Together they compound.
Why it feels like a good idea: two instincts collide there. The first is visual — a glass bottle in daylight looks lovely, and that is where people put beautiful objects. The second is a borrowed idea about ventilation: that fragrance needs air to travel. It does, but it needs gentle incidental air inside the room, not exchange with outdoors. Outdoor exchange is not distribution; it is removal.
Shop: the position that actually works is an entrance console or a sideboard near a doorway, and the compositions built for it are Garden Bloom at ₹799 for 50ml and Fresh Brew at ₹849. 130ml from ₹1,249 for 14–18 weeks. Free shipping above ₹499.
In this guide
Built for an entrance console
Garden Bloom · from ₹799
Fullest presence in the range
Fresh Brew 9.5 · from ₹849
If you have already lost a bottle
300ml oil refill · ₹2,399
Straight answer
Does a windowsill make a reed diffuser finish faster, and where should it go instead?
1. Yes, and it is the compound case. Everywhere else in a home you are usually fighting one accelerant. At a window you are fighting three — radiant sun, stored heat in the sill, and air exchange with outside — which is why the same bottle that lasts eight weeks in a hallway can struggle to reach five on a sill in May.
2. The air part is the one that also costs you presence. Sun and heat empty the bottle while the room still smells of something. Outdoor air movement empties it and takes the fragrance out of the window with it, which is why a windowsill bottle so often produces the complaint "it goes down fast and I cannot smell it".
3. Even a closed window is not neutral. Glass transmits heat all afternoon whether or not it opens, and a sealed sunlit sill is still one of the hottest surfaces in the flat.
4. There is a dust cost as well. Air from outside carries road dust, and dust settling on the exposed reed ends is one of the things that shortens the working life of the fibre. Reeds are the consumable in this format, and a window ages them faster.
5. Move it two feet, not two rooms. An inner-wall shelf, a sideboard near a doorway, an entrance console — waist to chest height, clear space around it, out of the beam. Stand it on a tray; the oil marks wood and stone.
6. Do not answer a window by buying a stronger scent. The room is not weak; the position is expensive. Composed and handmade in small batches in Pune, and a portion of every order supports girl-child education through Nanhi Kali.
2. The air part is the one that also costs you presence. Sun and heat empty the bottle while the room still smells of something. Outdoor air movement empties it and takes the fragrance out of the window with it, which is why a windowsill bottle so often produces the complaint "it goes down fast and I cannot smell it".
3. Even a closed window is not neutral. Glass transmits heat all afternoon whether or not it opens, and a sealed sunlit sill is still one of the hottest surfaces in the flat.
4. There is a dust cost as well. Air from outside carries road dust, and dust settling on the exposed reed ends is one of the things that shortens the working life of the fibre. Reeds are the consumable in this format, and a window ages them faster.
5. Move it two feet, not two rooms. An inner-wall shelf, a sideboard near a doorway, an entrance console — waist to chest height, clear space around it, out of the beam. Stand it on a tray; the oil marks wood and stone.
6. Do not answer a window by buying a stronger scent. The room is not weak; the position is expensive. Composed and handmade in small batches in Pune, and a portion of every order supports girl-child education through Nanhi Kali.
TL;DR: a window stacks sunlight, stored heat and outdoor air movement into one spot, so it empties a bottle faster than anywhere else and often leaves the room smelling of less. Two feet inward, out of the beam, near a doorway at waist to chest height. Costs nothing; usually improves the room.
Where the bottle should actually stand
SOSA Garden Bloom · British rose & night-blooming jasmine ₹799 / 50ml
Rounded, hotel-like and at 8.9 on our internal strength scale — a position at six reeds, not a concentration. It is in this guide because the entrance console is the position a windowsill is usually trying and failing to be: gentle incidental air from people arriving and leaving, no direct sun, no outdoor exchange, and the first thing anyone notices when the door opens. Alcohol-free, phthalate-free, on a heat-stable coconut-derived CCT base with six fibre reeds. 130ml ₹1,299 for 14–18 weeks.
Part one — three accelerants, one square foot
Most placement mistakes are single-variable. A bottle behind a sofa has a dead-air problem; a bottle on the fridge has a heat problem; a bottle under a split unit has a draught problem. The window is the only common position in an Indian home that supplies all three of the classic accelerants at once, and because they are independent they do not merely add — the hot oil is being carried off by moving air, so each makes the other more effective. That is the whole reason this article exists as something separate from a general guide to heat or to airflow.
1
ACCELERANT ONE · RADIANT SUN
Glass in a beam runs far hotter than the room
A bottle standing in direct sunlight is not at room temperature; it is being heated directly, and the liquid inside absorbs that energy efficiently. Warm oil is thinner, climbs the fibre faster and evaporates more readily off the tips — three accelerations from one variable, all of them working while you are out at the office and the beam is crossing the sill. There is a second, slower cost too: sunlight does not treat all aromatic materials equally, so a composition standing in a beam loses its lightest elements first and drifts base-heavy over time. Our whole range is designed to survive Indian heat on a stable CCT carrier, but no carrier can put back what a sunbeam has already driven out. Keeping a diffuser out of direct sunlight is on the label for exactly this reason.
The check: stand in the room at four in the afternoon and look for the beam, not at three in the morning when the sill looks harmless.
2
ACCELERANT TWO · THE SILL ITSELF
The hottest surface in the flat, hours after sunset
Fresh Brew₹849 · 9.5/10Indian window ledges are usually stone, tile or granite, sometimes with a metal frame, and all of those store heat well. They take in sun through the middle of the day and give it back through the evening, so a bottle can be in complete shade at seven o'clock and still standing on something distinctly warm. This is the accelerant that survives your fix if the fix is only a curtain. Drawing a sheer curtain removes the beam but leaves the ledge warm, which is why the honest advice is distance rather than shading — off the sill entirely, onto a wooden or ceramic surface further into the room. It also solves a second problem: reed oil marks stone and wood, and a sill is a difficult place to keep a tray.
The test: the back of your hand flat on the ledge at dusk. Warm to you is warm to the bottle.
3
ACCELERANT THREE · EXCHANGE, NOT AIRFLOW
Outdoor air removes fragrance rather than distributing it
A reed diffuser genuinely needs air movement — but the useful kind is the gentle incidental stirring of people walking past, which lifts fragrance off the reeds and folds it into the room. An open window does something different in kind. It exchanges the room's air with outside, so the fragrance you paid for is diluted into the street. Worse, moving outdoor air strips the saturated layer from the reed ends continuously, driving evaporation at its maximum rate. You get the fastest possible spend and the smallest possible return, at the same time. That is the signature complaint from a sill: the level drops visibly and nobody in the room can smell anything. Add the dust that comes in with it — settling on exposed fibre and shortening reed life — and the position has nothing left to recommend it.
Part two — not all windows are equally expensive
A north-facing window in a sheltered room is a very different proposition from a west-facing balcony door in Ahmedabad. The table below sorts them, and every figure in it is SOSA's own working guidance from in-house testing and customer correspondence rather than laboratory measurement.
The window ledger
Seven openings, ranked by what each costs a 50ml bottle
| Window and aspect | Sun on the glass | Air across the reeds | Rough cost to a 50ml | The better spot nearby |
|---|---|---|---|---|
| West-facing, opened daily ★ | Direct, hours of afternoon beam | Constant exchange with outside | Can cost a third to a half | Inner wall of the same room, out of the beam |
| Balcony door, left ajar | Varies, often direct | Heaviest exchange of all — a doorway to outdoors | Several weeks in an open month | The wall beside the door, indoors, waist height |
| South-facing, closed, sheer curtain | Diffused but persistent | None | A week or so, mostly from the warm ledge | Two feet inward on wood, off the stone |
| Kitchen window over the sink | Usually some | Extractor plus outdoor air | A week or more, plus a muddled smell | Out of the cooking zone entirely |
| Bathroom ventilator or louvre | Little | Continuous extraction to outside | Quiet room, fast bottle | A shelf on the opposite wall |
| North-facing, shaded, rarely opened | None to speak of | Minimal | Close to the rated window | Acceptable, though a doorway is still better |
| No window at all — inner console by a doorway | None | Gentle incidental traffic | Behaves as rated, and reads strongest | This is the reference position |
| The honest caveat: the fourth column ranks positions; it does not predict your bottle. A shaded balcony, a projecting chajja, double glazing, a high ceiling or a room that is opened for twenty minutes rather than all day will each move the number substantially. And one instruction overrides the whole table: never diffuse over live cooking. Extractor on, window open ten minutes, close up, then wait half an hour — fragrance layered onto cooking makes a third smell nobody designed. | ||||
Shop this guide
Three bottles for the positions that work
Garden Bloom · entrywaysfrom ₹799Shop → Fresh Brew · living roomsfrom ₹849Shop → Fresh & Grounded duo · 2 × 50ml₹1,548Shop →
The SOSA principle
Fragrance needs air to move it — but a window is not airflow, it is an exit.
Gentle incidental air inside the room distributes what the reeds release. Exchange with outdoors dilutes it into the street and empties the bottle at maximum rate while doing so.
Part three — why the sill feels right, and what to trust instead
I have stopped being surprised by how consistent this is. When a customer writes to say a bottle has run down early, and I ask where it stands, roughly half describe a window. There are two good reasons for that and neither is carelessness. The first is aesthetic: a glass bottle with six pale reeds in it is a beautiful object, and daylight is where beautiful objects go. The second is a piece of borrowed intuition — that fragrance needs air, that a stuffy room is the enemy, that putting scent near a window will let it travel through the house. The intuition is half right, which is what makes it so durable. Fragrance does need air movement. It needs the room's own air moving gently past the reeds and carrying molecules onward into the space, which is what happens when people walk through a doorway a few times an hour. What it must not have is air leaving the room, because the fragrance leaves with it.
The corrected instinct is worth stating as a rule, because it applies far beyond windows: put the bottle where people pass, not where air escapes. An entrance console is the best position in most Indian flats — a door that opens several times a day, people arriving and leaving, no sun, no exchange with outside except in brief bursts. A sideboard beside a doorway between two rooms is next. A dressing table or a bookshelf at waist to chest height in a bedroom works well. All of them are indoor positions with incidental traffic, and all of them will make a bottle both last longer and smell more present than the sill will. That combination — longer and stronger — is rare in this format, where almost every conservation move costs you something. It exists here because a window is not saving anything; it is simply wasting the bottle out of doors.
One more consequence, less obvious and worth knowing if you are wondering why your reeds look tired early. Air from outside carries dust, and Indian urban air carries a good deal of it. Dust settles on the exposed ends of the fibre, mixes with the residue that naturally accumulates there, and forms a crust that slows wicking. Reeds are the consumable in this format and oil is the stable part — people replace the oil and keep the reeds, when it is almost always the other way round. A bottle by an open window ages its fibre faster than one on an inner shelf, so if you have run a diffuser on a sill, refresh the reeds when you refill rather than pouring good oil through a set that has stopped working. We do not sell replacement reeds separately, which is an honest gap in our range and one I would rather name than pretend around; our guidance is to refresh them every few months.
Put the bottle where people pass, not where the air escapes.
— Sonal Sahani, SOSA
Part four — the two-foot move, and what it is worth
Every row below is a swap rather than a purchase, and all but the last two are free. This is the shortest useful table in the cluster because the answer really is that simple.
The relocation table
Instead of the window, and what the change returns
| Instead of… | Move it to… | What you keep | What you get back | Cost |
|---|---|---|---|---|
| A sunlit sill ★ | Entrance console or sideboard by a doorway | The whole configuration — six reeds, same scent | Weeks and presence together | Free |
| A ledge by a balcony door | The indoor wall beside the door, waist to chest height | The high-traffic advantage you wanted | The fragrance stops leaving the flat | Free |
| A stone sill you cannot avoid | A wooden or ceramic surface, on a tray | The same corner of the room | The stored-heat accelerant, removed | Free — a tray protects the surface |
| A kitchen window over the sink | Any shelf out of the cooking zone | A scented kitchen, minus the confusion | A clean smell instead of a layered one | Free |
| Replacing a bottle you lost to a sill | 300ml oil refill into your own vessel | Your glass, and the habit | About 8–11 months at roughly ₹7–8 per ml | ₹2,399 · oil only, no reeds |
| Two windowsill bottles in one big room | Two indoor positions at opposite ends | Both bottles, both behaving properly | Coverage a single point source cannot give | Duo set from ₹1,548 |
| Not the fix: a stronger fragrance | Nothing to buy — correct the position first | Your money | A 9.5 on a sunlit sill still behaves like a sunlit sill | Free advice |
Honest notes for buyers: the week-cost figures on this page are SOSA working guidance from in-house testing through 45°C heat and 85% monsoon humidity and from customer correspondence, not laboratory measurement; aspect, glazing, shading, ceiling height and how long a window stays open will all move them. Strength ratings quoted here are positions on SOSA's own internal scale at six reeds, not an industry standard and not a concentration. A larger bottle buys duration rather than volume — 130ml lasts 14–18 weeks against 6–8 and at six reeds projects about the same. Refills are oil only: remove the reeds, pour to the neck, return them and flip once so both ends are coated. Replacement reeds are not sold as a separate product; refresh them every few months. Reed oil never goes into a Sukoon, Boond or Megh, and the water-based Hotel Collection never goes into a reed bottle. Keep bottles out of direct sunlight, stand them on a tray, and keep them away from children and pets. Composed and handmade in small batches in Pune; a portion of every order supports girl-child education through Nanhi Kali.
Two indoor positions beat one bright one
SOSA Fresh & Grounded duo · Morning Freshness + Mountain Breeze ₹1,548 / 2 × 50ml
If the reason your bottle ended up on the sill is that the room is large and you were trying to get the fragrance to travel, the answer is more sources rather than a brighter spot. Output per bottle is fixed; the only way to raise the total in a room is another bottle. These two share green eucalyptus, so they meet rather than clash when used in adjoining spaces — Morning Freshness at 9.0 on our scale, Mountain Breeze at 9.4. Six fibre reeds each, 6–8 weeks apiece, and 2 × 130ml at ₹2,548 for 14–18 weeks.
SS
ISIPCA
Versailles
Versailles
A note from Sonal
Every brand in this category, including ours at the beginning, has photographed a reed diffuser on a windowsill in morning light. It is the obvious shot. The bottle is glass, the reeds are pale, the light is free, and it looks like exactly the kind of calm domestic moment the product is meant to belong to. I have come to think it is the most quietly misleading image we produce, because it teaches a placement that costs the buyer weeks of the thing they bought.
What convinced me was reading complaint messages side by side with photographs. People send pictures when something is wrong, and after a couple of hundred of them the pattern was impossible to miss: a bottle on a sill, half empty, with reeds that looked pale and dry at the top. Every one of those was three problems in a trench coat — sun, a hot ledge and air going out of the window — and every one of them was solved by a shelf two feet away.
So we say it on the label and we say it here. Keep it out of direct sunlight. Stand it on a tray. Put it where people pass, not where the air escapes. It is a strange thing for a shop to publish, since the fastest way to sell more bottles would be to let everyone keep them on the sill. But the range is composed and handmade in small batches in Pune to sit at a level it can hold for the whole life of a bottle, and I would rather you got all eight weeks of it. A part of every order funds a girl's classroom through Nanhi Kali.
Frequently asked questions
Does keeping a reed diffuser near a window make it finish faster?
Yes, usually faster than any other placement, because a window supplies three accelerants at once: direct sun heating the glass and oil, a ledge that stores and re-radiates heat, and air exchange with outdoors that strips the reeds. Our working guidance is that a sunlit, ventilated sill can cost a 50ml a third to a half of its stated 6–8 weeks in a hot month.
What if the window is closed and shaded?
Better, but still not neutral. Glass transmits heat even when shut, and stone or tile ledges store it and give it back after sunset. A north-facing, rarely opened window in a shaded room is close to acceptable. Anywhere else, two feet inward onto a wooden or ceramic surface will do more for the bottle than a curtain does.
Doesn't a reed diffuser need airflow to work?
It needs gentle incidental air inside the room — people walking past a console or through a doorway a few times an hour. Exchange with outdoors is the opposite: it removes fragrance rather than distributing it, so the level falls fast and the room reads flat. Dead air behind a sofa is the other failure mode, equally common and equally fixable.
Where is the best place to put a reed diffuser in an Indian flat?
An entrance console is the best single position in most homes: regular passing traffic, no sun, no outdoor exchange, and it greets everyone who arrives. A sideboard beside an interior doorway is next, then a dressing table or open shelf at waist to chest height. Keep clear space around the bottle, and stand it on a tray because reed oil marks wood and stone.
Does an open window damage the reeds themselves?
It ages them faster. Outdoor air carries dust, which settles on the exposed fibre, combines with the residue that accumulates naturally and slows wicking. Reeds are the consumable in this format and oil is the stable part, so if you have run a bottle on a sill, refresh the reeds rather than pouring a new ₹2,399 refill through spent ones. We do not sell reeds separately — an honest gap — and suggest refreshing every few months.
Reed diffuser longevity · placement · 2027
Off the sill and two feet inward. The best position in the house is usually the console by the door
SOSA reed diffusers from ₹749 for 50ml (6–8 weeks) and ₹1,249 for 130ml (14–18 weeks), six fibre reeds per bottle, alcohol-free and phthalate-free on a heat-stable coconut-derived CCT base tested through 45°C heat and 85% monsoon humidity. Duo sets from ₹1,498, and the oil-only refill ₹2,399 for 300ml. Free shipping above ₹499, and a portion of every order supports girl-child education through Nanhi Kali.
Shop the reed range → Oil refill from ₹2,399
Continue the read
More on why a bottle finishes early
- Does heat make it finish faster? — the largest single accelerant, isolated.
- Does air conditioning shorten it? — the draught and the dryness, separately.
- Why is my reed diffuser finishing so quickly? — all six accelerants, ranked.
- The complete longevity troubleshooting guide — this page and the eight around it, in one place.
- Brand: the SOSA founder story.
Editorial standards & sources
About this guide: Written by Sonal Sahani, ISIPCA Versailles-trained founder and perfumer at SOSA Home & Body, on why window and sill placement shortens the working life of a reed diffuser. The underlying relationships — temperature and viscosity, airflow and evaporation rate, air exchange and dilution — are standard physical principles; the specific week costs assigned to sills, balcony doors, kitchen windows and ventilators are SOSA working guidance from in-house testing and customer correspondence, not laboratory measurement, and vary with aspect, shading, glazing, ceiling height and how long an opening stays open. Strength ratings are positions on SOSA's internal scale at six reeds, not an industry standard. Refills are oil only; replacement reeds are not sold as a separate SOSA product.SOSA reed diffuser range & prices (verified August 2026): alcohol-free, phthalate-free, paraben-free and IFRA-compliant compositions on a heat-stable coconut-derived (CCT) carrier, low-VOC, supplied in a refillable glass bottle with six fibre reeds; 50ml lasts 6–8 weeks and 130ml lasts 14–18 weeks. Morning Freshness (Malabar lemon · peppermint · Nilgiri eucalyptus) 50ml ₹749 · 130ml ₹1,249 · 9.0/10; Garden Bloom (British rose · night-blooming jasmine) 50ml ₹799 · 130ml ₹1,299 · 8.9/10; Evening Calm (Kashmir lavender · chamomile) 50ml ₹799 · 130ml ₹1,299 · 8.9/10; Fresh Brew (Coorg coffee · Kerala vanilla) 50ml ₹849 · 130ml ₹1,349 · 9.5/10; Mountain Breeze (Himalayan pine · sage · Indian cedar) 50ml ₹849 · 130ml ₹1,349 · 9.4/10. Reed diffuser refills are oil only — you reuse your own vessel and reeds: 300ml ₹2,399 (roughly 8–11 months) · 500ml ₹3,499 (roughly 14–18 months), about ₹7–8 per ml against ₹15–17 per ml for a 50ml bottle. Duo sets ₹1,498–₹1,598 for 2 × 50ml and ₹2,498–₹2,598 for 2 × 130ml. Strength figures are positions on SOSA’s own internal strength scale, not an industry standard. Replacement reeds are not sold as a separate SKU; SOSA guidance is to refresh reeds every few months. The reed line is separate from the water-based Hotel Collection for ultrasonic machines (15ml ₹299 · 100ml ₹999 · 300ml ₹1,799) and the two are not interchangeable. Diffusers: Boond 300ml ₹899 · Sukoon 500ml ₹1,899 · Megh 6L ₹3,499 · waterless Vaayu ₹11,999. Composed and handmade in small batches in Pune, India; tested through 45°C summer heat and 85% monsoon humidity. Free shipping above ₹499. A portion of every order supports girl-child education through Nanhi Kali. Prices subject to change — see the live product pages.