Four when all three bedrooms have somebody sleeping in them. ₹7,596.
The test: for one week, note at midnight whether the third bedroom door is shut with a person behind it. Four nights or more out of seven and it earns a Sukoon. Fewer, and it does not.
2. Four is right when the flat is full. A household of five, or four with resident parents, uses all three bedrooms every night. Then there is no argument — four Sukoons at ₹7,596, one per occupied air space. Nothing about the square footage changes this; the occupancy does.
3. The test takes a week and costs nothing. For seven nights, note at midnight whether the third bedroom door is shut with somebody behind it. Four or more nights out of seven, buy the fourth machine. Three or fewer, do not — you have a room, not a bedroom.
4. The fourth machine costs more than ₹1,899. It is also a fourth tank to fill, a fourth plate to rinse and roughly a quarter more fragrance consumed across the year. A 100ml refill from ₹999 stretches noticeably less across four machines than three.
5. A Boond is the honest halfway house. If the third bedroom is small or occasional, a Boond at ₹899 covers up to 150 sq ft on a six-hour tank — enough for a guest room used a few nights a month. Three Sukoons plus a Boond is ₹6,596 against ₹7,596 for four Sukoons.
Made in India, composed by an ISIPCA Versailles-trained perfumer — and a portion of every order supports girl-child education through Nanhi Kali.
Why the fourth machine is a different kind of decision
The first three machines in a 3BHK are all buying the same thing: access to an air space you could not reach otherwise. Each one opens a room that no other machine can serve, because fragrance does not cross a shut door, so the value of machines one, two and three is straightforward and roughly equal. The fourth is not like them. It also opens an air space — the third bedroom is as sealed as the other two — but the question is whether anybody is inside it to receive what it produces. Fragrance has no value in an unoccupied room. It is not stored, it does not accumulate into something you enjoy later, and a scented room that nobody enters has converted ₹1,899 and a stream of refills into nothing whatsoever. This is the first point in the whole sequence where the marginal machine can be genuinely worthless rather than merely less useful.
The other thing that changes at four is the running cost, which people consistently underestimate because they price the decision as a one-off. Four tanks consume roughly a third more fragrance than three at the same doses and schedules, so the ₹1,899 recurs quietly as a larger refill bill every few months — a 100ml at ₹999 covers noticeably less ground across four machines. There is also a small administrative cost that nobody mentions: four machines is the point at which filling and rinsing stops being a thing you do and becomes a chore you skip, and a skipped machine is a machine with stale water in it. Three is a setup you maintain. Four is a setup you maintain only if all four rooms are giving you something back every night.
The three decisions between three and four
SOSA Sukoon₹1,899This is deliberately crude, because crude tests get done. For one week, on your way to bed, note whether the third bedroom door is shut with a person behind it. Count the nights. Four or more out of seven means that room is a bedroom and earns a Sukoon; three or fewer means it is a room with a bed in it, which is a different thing. The reason for using nights rather than hours is that bedrooms earn their machines at night — a room used as a study from ten to six is served by the public zone whenever its door is open, and a study with the door shut is a place you concentrate rather than a place you notice a fragrance.Three or four, household by household
The decision tracks occupancy, not area — a 1,200 sq ft 3BHK with five people in it needs more machines than a 1,600 sq ft one with two. Coverage ratings assume a closed room without a strong draught, and every figure below assumes one machine per occupied air space.
| Household | Bedrooms slept in | What to buy | Total |
|---|---|---|---|
| Couple, no children ★ | One | Two Sukoons — public zone and master. The other two rooms are an office and a store | ₹3,798 |
| Couple with one child ★ | Two | Three Sukoons — zone, master, child's room | ₹5,697 |
| Two working flatmates | Two | Three Sukoons — zone and both occupied bedrooms | ₹5,697 |
| Family with two children | Three | Four Sukoons — zone and all three bedrooms | ₹7,596 |
| Family with resident parents | Three | Four Sukoons, or three Sukoons plus a Boond if the third room is small | ₹7,596 or ₹6,596 |
| Couple with a real guest room | One, plus visitors | Two Sukoons plus a Boond switched on when guests come | ₹4,697 |
| The test, again: for one week, note at midnight whether the third bedroom door is shut with somebody behind it. Four nights or more out of seven and it earns a Sukoon. Three or fewer and it earns, at most, a ₹899 Boond. | |||
Sukoon · three or four₹1,899Shop → 
Boond · the occasional room₹899Shop → 
Hotel Collection · the scentFrom ₹299Shop →
Placement, drops and running three or four machines
With three machines the arrangement is straightforward. The public-zone unit stands about a metre up on a console, angled towards the seating and away from the passage mouth, at five to six drops. The two bedroom units sit two or three feet clear of their bedheads at three to four drops, on the 2H timer. Keep all of them out of the direct line of a ceiling fan or a split AC, which pushes mist against one wall rather than spreading it, and leave a foot of clear air around each so the output disperses instead of condensing on a curtain.
Adding the fourth changes one thing you might not anticipate: two bedrooms will now sit either side of the same stretch of passage, and their fragrances will meet whenever both doors are open. Use the same scent in both, or two that share a note — cedar, white tea or a soft amber running through each — rather than two unrelated fragrances. This is the practical argument for keeping a 3BHK to two scents total: it stops the private half of the flat from becoming a corridor of samples. If the fourth machine goes into a smaller room, drop it to two or three drops rather than matching the master.
The running schedule matters more with four than with three, because consumption scales with tanks rather than with rooms you notice. Run the public zone on 4H from early evening and each bedroom on 2H before sleep; nothing overnight, nothing while the flat is empty. Rinse tanks when you change scents, use filtered water in hard-water cities, and never substitute raw essential or carrier oils, which are too viscous to atomise and will foul the misting plate. Three to six drops of Hotel Collection per tank is the general guidance across every machine in the flat.
Three against four, costed
The two setups side by side with the intermediate options, every total checked. Each Sukoon includes three 15ml fragrances of your choice, so the machine price is the day-one price in every row.
| Setup | What you get | Covers | Total |
|---|---|---|---|
| Two machines | Two Sukoons ₹1,899 × 2 — 6 × 15ml scents | Public zone + master | ₹3,798 |
| Three ★ | Three Sukoons ₹1,899 × 3 — 9 × 15ml scents | Zone + two occupied bedrooms | ₹5,697 |
| Three and a half | Three Sukoons ₹5,697 + one Boond ₹899 | Zone + two bedrooms + occasional room | ₹6,596 |
| Four | Four Sukoons ₹1,899 × 4 — 12 × 15ml scents | Zone + all three bedrooms | ₹7,596 |
| Running cost | A 100ml refill from ₹999, or 300ml ₹1,799 (~₹6/ml) | Roughly a third less per machine at four | from ₹999 |
Versailles
I would rather sell three machines that all get used than four where one sits dark. That is not modesty, it is self-interest over a longer horizon: the person with a dark diffuser on a shelf does not buy refills, and does not recommend us.
What I have learnt from 3BHK households specifically is that the third bedroom changes identity roughly every two years. It is a guest room, then a nursery, then a home office, then a teenager's room. Buying hardware for the version of the room that exists today is fine; buying it for the version you imagine is how people end up with a machine that has never been filled twice. The test exists because I could not find a gentler way of asking whether the room is currently real.
So run the week. Three Sukoons at ₹5,697 for most households, four at ₹7,596 for a full one, and a ₹899 Boond for the room in between. Buy the fourth in month three rather than week one if you are unsure — it costs the same and you will know. A portion of every order supports girl-child education through Nanhi Kali.
Frequently asked questions
- How many diffusers do you need for a 3BHK? — the count, zone by zone.
- How to scent a 3BHK without buying five machines — the frugal two-machine route.
- 3BHK scenting budget — purchase and running costs in full.
- Two or three Sukoons for a 2BHK? — the same question one flat size down.
- Brand: the SOSA founder story.
SOSA products & prices (verified August 2026): Hotel Collection water-based ultrasonic diffuser fragrance 15ml ₹299 · 100ml ₹999 · 300ml ₹1,799 · Pack of 7 (15ml, all fragrances) ₹1,799; refills 100ml 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). Diffusers: Boond 300ml ₹899 · Sukoon 500ml ₹1,899 · Megh 6L ₹3,499. Water-based, phthalate-free, composed to IFRA standards for home diffusion; 3–6 drops per tank. Made in India, Pune. The Hotel Collection scents are SOSA's own interpretations inspired by the world's finest hotels; all hotel names are trademarks of their respective owners and are used only to describe the scent style — SOSA is an independent Indian fragrance house, not affiliated with or endorsed by any hotel brand. Prices and availability subject to change — see the live product pages.