The three new ones: nothing at the foot of the stairs, the landing is a junction rather than a room, and the upstairs unit sits away from the stairwell.
The landing: a Boond at ₹899, set back from the balustrade rather than beside it.
2. Never at the foot of the stairs. It is the most tempting position in a duplex — the console table and the socket are usually there — and it is the one place where the stairwell collects the machine's output and delivers it to the landing ceiling before it has done anything for the room it is standing in.
3. The landing is a junction, not a room. It has a void on one side and bedroom doors on the other, so a 500ml unit rated for 270–320 sq ft is the wrong scale there. A Boond at ₹899, set back from the balustrade rather than beside it, is the right one.
4. Upstairs, keep the machine away from the stairwell. A unit near the landing door sits in the draught and loses part of its output to the void every time the door opens. Put it on the far side of the bedroom, across from the pillow and at least 1.5m away, on low with the 2H timer.
5. Downstairs, go central and high rather than strong. Central to the open volume, at 90–120cm, on the line the air already takes from front door to balcony — and as far from the stairwell as the furniture allows.
A portion of every order supports girl-child education through Nanhi Kali.
The three rules a two-storey home adds
Placement in a flat is a question about a room: where in this volume does the machine do most good. Placement in a duplex is a question about a building, because one feature of the building overrides every room-level decision you might otherwise make. The staircase is the strongest, steadiest and most predictable airflow in the house, it runs whether or not anybody is home, and it only goes one way. Three of your positions are decided by it, and getting those three right matters more than anything else on this page.
Where each machine goes, floor by floor
The positions, the settings and the two places that still get nothing at all. Read the last column rather than copying the middle one, because the reasoning travels between houses and the furniture does not.
| Where | The position | Setting | Why there |
|---|---|---|---|
| The open lower floor ★ | Central to the volume at 90–120cm on a console — as far from the foot of the stairs as the furniture allows, and not beside the kitchen zone | Steady or the 4H timer while people are home | The largest air mass in the house and the one continuously losing its warm upper layer. Distance from the stairwell matters more here than anything else |
| The landing | A Boond at ₹899 on a console or shelf against the bedroom-door wall, set back from the balustrade | Low | A junction rather than a room. Against the wall its output enters the landing; at the edge it goes over the void |
| Master bedroom upstairs | On a chest of drawers on the far side of the room from the landing door, across from the pillow and at least 1.5m away | Low, 2H timer | Well inside a 270–320 sq ft rating, so restraint is the skill. Away from the door means away from the draught the stairwell creates |
| Second and third bedrooms upstairs | Same rule — solid wall rather than the void side, far side from the door | Low, 2H timer | Each is a separate air mass with its own door and its own occupant, and each is unreachable from anywhere else in the house |
| A ground-floor guest bedroom or study | Normal room rules — 90–120cm, hard surface, away from the doorway onto the open floor | Low, or the 4H timer across a working afternoon | It earns a machine on conscious hours rather than floor area. If it is used four times a year, reeds from ₹749 instead |
| The staircase itself and the bathrooms | Nothing on the stairs; a Boond at ₹899 on a bathroom shelf if anything | Low | A staircase is a route rather than a room, and anything placed on it is placed in a draught. Extraction and dry floors come first in a bathroom |
Sukoon · 90–120cm, away from the stairwell₹1,899Shop → 
Boond · the junction at the top₹899Shop → 
Vaayu · the volume below₹11,999Shop →
Why the stairwell decides half the plan
It is worth spending a moment on why one architectural feature is allowed to overrule so many room-level decisions, because once the mechanism is clear the three rules stop needing to be remembered. Warm air is less dense than cool air and rises; an open stairwell gives the warm upper layer of the lower floor a continuous vertical route; cooler air draws in below to replace it. That circulation runs all day, is far stronger and steadier than anything a diffuser produces, and is entirely indifferent to your furniture. Fragrance is carried by air rather than travelling through it under its own power, so wherever you place a machine, the question that actually matters is which current its output joins. Place it at the foot of the stairs and it joins the strongest current in the house, which is going somewhere you did not intend. Place it central and high on the same floor and it joins the room's own slower circulation, which is what a 270–320 sq ft rating assumes. Height still helps for the reason it always did — cool mist is denser than room air and descends as it spreads, so a unit at ankle height scents the lowest third of a room while one at 90–120cm distributes into it — and in a duplex height and distance from the stairwell are the two levers that do nearly all the work. Nothing on the machine itself does anything comparable: output is a rate of 30–50 ml/h into whatever air is available rather than a distance, so turning it up only makes the corner near it heavier and drops runtime from 16–18 hours to 9–12 on the same 500ml fill.
The second thing the stairwell decides is the refill route, which sounds like housekeeping and is genuinely a placement constraint at three or four machines. A 500ml tank wants emptying, rinsing and a wipe at the misting plate on a regular morning, with filtered or RO water in hard-water cities, and in a two-storey home that circuit has a staircase in the middle of it. The sensible version is one lap that collects the upstairs tanks on the way down rather than two separate trips, which means placing every unit where you can lift it one-handed from a clear surface at 90–120cm — not behind a lamp, not wedged between photo frames, not on the shelf that also holds the books, and not on the one surface in the house that would genuinely mind a spill. Carrying a full 500ml tank down a flight of stairs is the specific thing to design out, so fill upstairs tanks from a jug carried up rather than carrying tanks down full, and do all of them on the same morning rather than reacting to whichever has run dry. Done as one deliberate circuit, three machines is about ten minutes and a habit; done reactively it becomes a rota nobody owns, and the failure mode is two machines standing quietly dry by March. Keep each room's bottle in that room rather than in one cupboard, so nobody has to carry fragrance up and down either, and never layer a new scent onto a half-rinsed tank — empty, rinse, wipe, refill.
Which brings the placement decision that is really a purchasing decision, and I would rather set it out here than pretend the two are separate. The machine that generates most of the work in a duplex is the downstairs one, because it runs the longest hours, empties fastest and belongs to nobody in particular, while an upstairs bedroom unit on low with the 2H timer goes most of a week on one fill. It is also the machine fighting the stairwell. So if you have placed a Sukoon on the open lower floor, raised it to 90–120cm, moved it central and as far from the stairs as the room allows, and after a fortnight the ends of an 800–1,300 sq ft floor still read thin — or the living area is double-height, in which case the volume grew without the floor plan changing — you have arrived at the point where the honest answer changes technology rather than adding another tank. A second ultrasonic unit at the far end of the same open floor is not the fix: two machines in one air mass overlap in the middle rather than adding their ratings together, so the centre gets heavier and the ends stay much as they were, and that ₹1,899 would have finished a bedroom upstairs. A waterless Vaayu at ₹11,999 is: a cold-air nebuliser running undiluted oil with no tank at all, rated for up to 1000m³ of connected space, adding no humidity, under 38dB, with a Bluetooth app and genuine scheduling where the Sukoon's steady, 2H and 4H timers are duration timers that cannot start the machine at a clock time. Place it in that connected volume, keep the Sukoons upstairs, keep the Boond on the landing, and the house is ₹17,696 with three bedroom machines. It still will not open a bedroom door and it still will not climb the stairs to any useful effect, which is exactly why it is an addition to the placement plan rather than a replacement for it.
The SOSA duplex edit
Placement as a shopping list, because most of it is free and the rest is deciding which machine belongs in which kind of volume. The last two rows are the positions to avoid.
| Buy or do | What it does | When it earns its place | Price |
|---|---|---|---|
| 1. Height, hard surface, distance from the stairwell ★ | Every unit at 90–120cm on glass, stone, laminate or sealed wood, central to its own room and as far from the staircase as the furniture allows — the change that does most for coverage in a two-storey home | Before buying anything else. It is free and it is the biggest single improvement | Free |
| 2. Three Sukoons — one below, two above | 270–320 sq ft each, one per enclosed room per floor, bedroom units on low with the 2H timer and 1.5m from the pillow — nine 15ml Hotel Collection bottles between them | One per enclosed room somebody is awake in | ₹5,697 |
| 3. Boond 300ml on the landing | The junction of the two storeys, set back from the balustrade rather than beside it, on bottles you already own | Once each floor has its own machine. The best ₹899 in the house | ₹899 |
| 4. Vaayu for the open lower floor | Up to 1000m³ with no tank at all, no added humidity, under 38dB and app scheduling — placed central to the living, dining and entrance as one volume | Only after height, central placement and distance from the stairs have been tried | ₹11,999 |
| Not this: a machine at the foot of the stairs | Output fed straight into the strongest current in the house, arriving at the landing ceiling rather than in the room | Never. Use a worse height and a better position instead | ₹1,899 |
| Not this: a Sukoon on the landing | A 500ml unit rated for 270–320 sq ft at a junction with a void on one side — most of it goes over the balustrade | Never. The landing wants ₹899, not ₹1,899 | ₹1,899 |
Versailles
Placement is the part of this I would most like duplex owners to take seriously, because it is free and because in a two-storey home it is worth more than an extra machine. The commonest arrangement I am shown is the same one every time: a beautiful diffuser on the console table at the bottom of the stairs, where the socket is, doing almost nothing for the room it is in and quietly perfuming a ceiling nobody looks at. Moving that one machine three metres and raising it half a metre has fixed more duplexes than anything I have ever sold anybody.
Nothing at the foot of the stairs, something small and set back on the landing, and the upstairs units against the solid wall rather than the void. Then do the thing almost nobody does before ordering, which is to walk the refill route with a staircase in the middle of it and ask whether you would happily carry a full 500ml tank down it on a Sunday morning in a bad mood. If the answer is no, move the machine or fill it from a jug carried up — because a machine that is awkward to refill is a machine that will be standing dry by March. And if the walk itself is what puts you off, that is worth listening to: the downstairs machine is where the work is, and a machine with no tank in it is an honest answer to that half of the house.
Everything is made and supported from Pune, and a part of every order funds girl-child education through Nanhi Kali. You get a home that smells like somewhere you chose; a girl gets a classroom. That equation has always felt right to me.
Frequently asked questions
- Can one Sukoon fragrance more than one floor? — what actually happens when people try.
- Do you need a separate ultrasonic diffuser on each floor of a duplex? — the staircase, in full.
- Best upstairs and downstairs fragrance combination for a duplex — which scent belongs on which floor.
- The complete SOSA Sukoon and Vaayu buying guide for duplex homes — the pillar guide.
- Brand: the SOSA founder story.
Facts verified August 2026: SOSA Sukoon — 500ml tank, 2.4MHz ultrasonic cool mist, 270–320 sq ft coverage, 16–18 hours runtime on low and 9–12 on high, 30–50 ml/h mist output, 7-colour LED, remote and steady/2H/4H timers, BPA-free ABS with auto shut-off and overheat protection, ~17cm high — ₹1,899, including three 15ml Hotel Collection fragrances of your choice. Boond 300ml ₹899; Megh 6-litre ₹3,499. Hotel Collection water-based fragrance 15ml ₹299, 100ml ₹999, 300ml ₹1,799, Pack of 7 × 15ml ₹1,799; 100ml and 300ml refills from ₹999. Seven scents: The Ritz-Carlton-inspired (white tea, bergamot, cedar), Westin-inspired (white tea, aloe, cedar), 1 Hotels-inspired (cedarwood, vetiver, green leaves), The St. Regis-inspired (amber, violet, woods), Shangri-La-inspired (jasmine, green tea, white tea), Four Seasons-inspired (citrus, floral, sandalwood), W Hotels-inspired (citrus, pepper, amber). Waterless systems for larger and connected spaces: Vaayu ₹11,999 (up to 1000m³), Aangan ₹25,999 (8,000–10,000 sq ft), Meenar ₹38,500 (12,000–18,000 sq ft). The Hotel Collection scents are SOSA's own interpretations; SOSA is not affiliated with or endorsed by any hotel brand. Prices subject to change — see the live product pages.