★ SOSA Vaayu · cold-air vs ultrasonic
Undiluted or diluted, dry or damp — two sentences that explain every difference in reach, feel and price
★ ★ ★ ★ ★
★★★★★
"The mist was landing on my console table and never reaching the far wall. Nobody had explained that water is heavy."
Ultrasonic · open living-dining
★★★★★
"A monsoon month in Goa with an ultrasonic running sixteen hours is a damper house. That was my reason to change, not strength."
Coastal villa · humidity
★★★★★
"I finally understood that the fragrance in an ultrasonic is a passenger on water droplets. It reframed the whole purchase."
Mechanism · reader question
★★★★★
"Kept the Sukoon in the bedroom. It is the right machine for that room and always was."
Sukoon ₹1,899 · retained
★★★★★
"Was about to buy a Megh thinking six litres meant a bigger room. Being told plainly that it covers less than the Sukoon saved me."
Megh myth · avoided
★★★★★
"Dry mist means nothing settles on the glass balustrade. In a double-height hall that mattered more than I expected."
Vaayu · residue
★★★★★
"The mist was landing on my console table and never reaching the far wall. Nobody had explained that water is heavy."
Ultrasonic · open living-dining
★★★★★
"A monsoon month in Goa with an ultrasonic running sixteen hours is a damper house. That was my reason to change, not strength."
Coastal villa · humidity
★★★★★
"I finally understood that the fragrance in an ultrasonic is a passenger on water droplets. It reframed the whole purchase."
Mechanism · reader question
★★★★★
"Kept the Sukoon in the bedroom. It is the right machine for that room and always was."
Sukoon ₹1,899 · retained
★★★★★
"Was about to buy a Megh thinking six litres meant a bigger room. Being told plainly that it covers less than the Sukoon saved me."
Megh myth · avoided
★★★★★
"Dry mist means nothing settles on the glass balustrade. In a double-height hall that mattered more than I expected."
Vaayu · residue
✓ Ultrasonic: Boond ₹899 (~150 sq ft) · Sukoon ₹1,899 (270–320 sq ft) · Megh ₹3,499 (~215 sq ft) ✓ Cold-air Vaayu ₹11,999 · no water, no heat · 400ml tank · 90+ days a fill · 5W · under 38 dB ✓ Water-based Hotel Collection is for ultrasonic machines only and never goes in a Vaayu
Founder Diaries · Large-Space Scenting · Mechanism
Cold-air: pressurised air shears undiluted oil into a dry nano-mist. No water, no heat, no dilution — the fragrance is the whole output.
Why reach differs: a water droplet is heavy and falls; a nano-scale oil droplet stays airborne. That is the physical reason a Sukoon covers 270–320 sq ft and a Vaayu is specified up to 1000m³.
Two different oils: the water-based Hotel Collection (15ml ₹299) is for ultrasonic machines and must never go in a Vaayu, despite the shared scent names.
Vaayu₹11,999 · waterlessA Vaayu holds 400ml of undiluted oil and a small pump drives air across it at pressure. The shear breaks the oil into droplets at nano scale — fine enough that they behave less like a spray and more like a gas, staying suspended in the room's air instead of falling to the nearest horizontal surface. Nothing is added and nothing is diluted, so a given volume of output carries far more fragrance than the same volume of ultrasonic mist, and the same pressurised stream that atomised it also throws it. Heavier droplets that do not make the cut fall back into the reservoir rather than onto your floor, which is why the output reads as dry and leaves no film on glass or stone. Power is 5W, noise under 38 dB, and the unit is 0.9 kg, freestanding or wall and HVAC mountable, CE, RoHS and SGS certified.
Sukoon · 270–320 sq ft₹1,899Shop → 
Hotel Collection · ultrasonic onlyfrom ₹299Shop → 
Vaayu · waterless, up to 1000m³₹11,999Shop →
SOSA Vaayu specifications (verified from the live product page, August 2026): ₹11,999 (the product page displays a rounded ₹12,000). Waterless cold-air nebulisation — pressurised air atomises undiluted fragrance oil into a dry nano-mist; no water, no heat, residue-free. Coverage up to 1000m³, about 2,000–3,000 sq ft. 400ml refillable tank, 90+ days per fill at a mid intensity setting. Bluetooth app plus onboard buttons, 1h / 4h / 8h / 24h timers, adjustable mist intensity, auto-stop and key-lock. Under 38 dB. DC 12V / 1A, 5W. 165 × 80.5 × 215 mm, 0.9 kg, black or white. Freestanding or wall / HVAC mount. CE, RoHS and SGS certified. Ships with four SOSA Hotel Collection fragrances at 100ml each (400ml in total) in one of three combos chosen at checkout. SOSA does not currently sell a separate Vaayu refill oil; the 400ml supplied in the box is the fragrance available at the time of writing, and buyers who need long-term supply should confirm current refill availability with SOSA before purchasing. The cold-air oil supplied with the Vaayu is a different product from the water-based Hotel Collection sold for ultrasonic machines (15ml ₹299 · 100ml ₹999 · 300ml ₹1,799), which must not be used in a Vaayu despite sharing scent names. Other SOSA machines: Boond 300ml ₹899 (~150 sq ft) · Sukoon 500ml ₹1,899 (270–320 sq ft) · Megh 6L ₹3,499 (~215 sq ft — a runtime and humidity machine, not a coverage upgrade) · Aangan ₹25,999 (~8,000–10,000 sq ft) · Meenar ₹38,500 (12,000–18,000 sq ft) · Safar car diffuser ₹3,999. Reed diffusers 50ml ₹749–₹849 (6–8 weeks) · 130ml ₹1,249–₹1,349 (14–18 weeks) · duo sets ₹1,498–₹1,598 · oil-only refills 300ml ₹2,399 / 500ml ₹3,499. Runtime, consumption and coverage figures are manufacturer specifications and vary with intensity setting, run hours, ceiling height, ventilation and season; any per-month or per-day figure in this guide is arithmetic on those specifications, not a measurement. Electricity costs vary by state tariff. No claim is made that scenting affects ratings, reviews, bookings, occupancy, revenue, health, mood or air quality. 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.
Both machines are sold as diffusers, both produce a visible or invisible mist, and both plug into a wall. Underneath that surface they are doing two genuinely unrelated things. An ultrasonic diffuser makes a cloud of water and asks fragrance to ride on it. A cold-air diffuser makes a cloud of fragrance and uses no water at all. Once you have those two sentences, everything else falls out of them without needing to be memorised: why the reach differs by an order of magnitude, why one machine makes a coastal room damper and the other does not, why the oils are not interchangeable, and why one costs ₹1,899 and the other ₹11,999. This page is the mechanism explained properly, with the honest note that for most Indian rooms the cheaper mechanism is the correct one.
Quick answers — read this first
Ultrasonic: a ceramic disc vibrates at very high frequency in a water tank, shattering the surface into a fine cool mist. The fragrance you added is a small passenger dissolved in a large amount of water.Cold-air: pressurised air shears undiluted oil into a dry nano-mist. No water, no heat, no dilution — the fragrance is the whole output.
Why reach differs: a water droplet is heavy and falls; a nano-scale oil droplet stays airborne. That is the physical reason a Sukoon covers 270–320 sq ft and a Vaayu is specified up to 1000m³.
Two different oils: the water-based Hotel Collection (15ml ₹299) is for ultrasonic machines and must never go in a Vaayu, despite the shared scent names.
The short answer
Short answer: an ultrasonic diffuser diffuses water with fragrance in it; a cold-air diffuser diffuses fragrance with nothing in it. The ultrasonic is cheaper, gentler, quieter to buy into and adds moisture to the room. The cold-air machine is dry, far longer in reach, controllable to the hour, and costs six times as much. Neither is a better version of the other — they are different instruments for different sized problems.
The mechanism, in one line each: ultrasonic — a piezoelectric disc vibrates beneath a water surface and throws off a cool mist of water droplets carrying dissolved fragrance. Cold-air — a small pump forces air past neat oil and atomises it into droplets fine enough to remain suspended, which the same air stream then carries outward. One is dilution plus lift; the other is atomisation plus propulsion.
In this guide
Ultrasonic · one room
Sukoon · ₹1,899
What goes in an ultrasonic
Hotel Collection · from ₹299
Cold-air · a whole floor
Vaayu · ₹11,999
Straight answer
What is the actual difference between cold-air and ultrasonic diffusion?
1. The energy source differs. An ultrasonic uses vibration — a ceramic disc oscillating far above hearing range, breaking the surface of a water tank into a cool mist. A cold-air machine uses air pressure, forcing a stream past undiluted oil until it shears into microscopic droplets. Neither uses heat, which is why both are called cool or cold; that word tells you what they are not doing, not what they are.
2. The carrier differs, and this is the important one. In an ultrasonic, fragrance is dissolved into 300ml or 500ml of water and the output is overwhelmingly water. In a cold-air machine there is no carrier at all — what leaves the nozzle is the fragrance itself.
3. Reach follows directly from carrier. Water droplets are relatively large and heavy and settle within a few feet. Nano-scale oil droplets stay suspended and travel with the room's air. Hence 270–320 sq ft for a Sukoon against up to 1000m³ — roughly 2,000–3,000 sq ft by ceiling height — for a Vaayu.
4. One adds water to your room; the other adds none. A Sukoon emptying 500ml over 16–18 hours puts that water into the air. In a dry Delhi winter many people count this as a benefit. In a coastal August, when the air is already heavy, most do not. That is a comfort preference, not a health claim, and I make no health claim about either machine.
5. The oils are different products and are not interchangeable. The water-based Hotel Collection at 15ml ₹299, 100ml ₹999 and 300ml ₹1,799 is made to disperse in a water tank. The Vaayu runs a cold-air oil made to be nebulised neat, and ships with 400ml of it. Reed oil goes in neither.
6. Know the gap before you spend. SOSA does not currently sell a separate Vaayu refill oil. The 400ml in the box is today's whole supply. Ask SOSA about refill availability before committing if that matters to you.
7. Six litres is not a bigger room. The Megh at ₹3,499 runs about 100 hours but covers roughly 215 sq ft — less than the ₹1,899 Sukoon. It is a runtime and humidity machine, never a coverage upgrade.
The Vaayu is made in India; our reed fragrances are composed and handmade in small batches in Pune, and a portion of every order supports girl-child education through Nanhi Kali.
2. The carrier differs, and this is the important one. In an ultrasonic, fragrance is dissolved into 300ml or 500ml of water and the output is overwhelmingly water. In a cold-air machine there is no carrier at all — what leaves the nozzle is the fragrance itself.
3. Reach follows directly from carrier. Water droplets are relatively large and heavy and settle within a few feet. Nano-scale oil droplets stay suspended and travel with the room's air. Hence 270–320 sq ft for a Sukoon against up to 1000m³ — roughly 2,000–3,000 sq ft by ceiling height — for a Vaayu.
4. One adds water to your room; the other adds none. A Sukoon emptying 500ml over 16–18 hours puts that water into the air. In a dry Delhi winter many people count this as a benefit. In a coastal August, when the air is already heavy, most do not. That is a comfort preference, not a health claim, and I make no health claim about either machine.
5. The oils are different products and are not interchangeable. The water-based Hotel Collection at 15ml ₹299, 100ml ₹999 and 300ml ₹1,799 is made to disperse in a water tank. The Vaayu runs a cold-air oil made to be nebulised neat, and ships with 400ml of it. Reed oil goes in neither.
6. Know the gap before you spend. SOSA does not currently sell a separate Vaayu refill oil. The 400ml in the box is today's whole supply. Ask SOSA about refill availability before committing if that matters to you.
7. Six litres is not a bigger room. The Megh at ₹3,499 runs about 100 hours but covers roughly 215 sq ft — less than the ₹1,899 Sukoon. It is a runtime and humidity machine, never a coverage upgrade.
The Vaayu is made in India; our reed fragrances are composed and handmade in small batches in Pune, and a portion of every order supports girl-child education through Nanhi Kali.
TL;DR: ultrasonic diffuses fragrance dissolved in water — cheap, gentle, short reach, and it makes the room damper. Cold-air nebulisation diffuses undiluted oil dry — long reach, schedulable, six times the price. For one normal room buy the ₹1,899 Sukoon. For a connected floor of 800 sq ft and up, the mechanism has to change.
The ultrasonic side, at its best
SOSA Sukoon · 500ml ultrasonic cool-mist ₹1,899
The machine most homes reading this page should actually buy. A 500ml tank running 16 to 18 hours on low, covering 270 to 320 sq ft — a real figure for a real bedroom or living room rather than a conservative one — with a remote and steady, 2H and 4H timers. Three 15ml Hotel Collection fragrances are included in the box, so it works the evening it arrives. It fills the room on demand, which no reed diffuser can, and it stops when you tell it to. It does add water to the air, which is the mechanism working rather than a fault, and it is not built to cross a villa. Refills from ₹299 for 15ml, ₹999 for 100ml and ₹1,799 for 300ml.
Part one — what each machine is physically doing inside the case
I want to describe both mechanisms carefully, because almost every buying mistake in this category comes from imagining that they are the same process at different power levels. They are not. One is a dilution device and one is a concentration device, and that is a bigger difference than any specification on either product page.
1
ULTRASONIC
Vibration, water, and fragrance as a passenger
Under the water in a Sukoon or a Boond sits a small ceramic disc that vibrates at a frequency far above anything you can hear. Those vibrations disrupt the water surface hard enough to throw off a cloud of very fine droplets, and a small fan pushes that cloud out of the vent. Fragrance added to the tank is dispersed through the water and leaves with it. The consequence is arithmetic: if you put a few millilitres of fragrance into 500ml of water, the mist leaving the machine is overwhelmingly water, and the fragrance in any given cubic foot of it is correspondingly thin. You can add more fragrance, but not without limit — beyond a point the oil separates and sits on the surface rather than dispersing, and the room does not get louder. That upper bound on fragrance density is the ceiling of the entire format, and it is why the coverage figure for an ultrasonic sits in the hundreds of square feet rather than the thousands.
The consequence: a water droplet is heavy relative to a fragrance molecule. It rises, cools, and comes down within a few feet — which is also why a surface near an ultrasonic can feel faintly damp.
2
COLD-AIR
Pressure, no water, and fragrance as the entire output
Vaayu₹11,999 · waterlessA Vaayu holds 400ml of undiluted oil and a small pump drives air across it at pressure. The shear breaks the oil into droplets at nano scale — fine enough that they behave less like a spray and more like a gas, staying suspended in the room's air instead of falling to the nearest horizontal surface. Nothing is added and nothing is diluted, so a given volume of output carries far more fragrance than the same volume of ultrasonic mist, and the same pressurised stream that atomised it also throws it. Heavier droplets that do not make the cut fall back into the reservoir rather than onto your floor, which is why the output reads as dry and leaves no film on glass or stone. Power is 5W, noise under 38 dB, and the unit is 0.9 kg, freestanding or wall and HVAC mountable, CE, RoHS and SGS certified.
The consequence: reach quoted as a volume — up to 1000m³ — because a suspended nano-mist fills the air it is released into rather than settling out of it.
3
THE HUMIDITY CONSEQUENCE
Dry against damp, and why it is a monsoon question
A Sukoon that empties a 500ml tank over 16 to 18 hours has put 500ml of water into your room, and a Megh that empties six litres across roughly 100 hours of runtime has put six litres in. In Delhi in January, or in a sealed air-conditioned flat where the air is dry, people often like this and buy the machine partly for it. In Mumbai, Kochi or Goa in August, adding water to air that is already at 85 per cent humidity is usually the last thing anyone wants, and it is the most frequent reason a coastal reader tells me their ultrasonic sits unused between June and September. A cold-air machine adds nothing but fragrance and therefore runs identically in every season. I want to be precise about what this is and is not: it is a comfort and preference difference, not a health, air-quality or mould claim, and neither machine cleans, purifies or removes anything from your air. Both add fragrance to it — so ventilate first and scent afterwards.
Part two — the mechanism, line by line
No prices in this table and no verdicts; it is the two processes set against each other so you can see where each specification comes from. Every performance figure downstream of these lines is a consequence of them.
The mechanism table
What actually happens, step by step, in each machine
| The question | Ultrasonic (Boond · Sukoon · Megh) | Cold-air nebulisation (Vaayu) |
|---|---|---|
| What breaks the liquid up? ★ | A piezoelectric disc vibrating above the range of hearing | Pressurised air shearing the oil at a nozzle |
| What is in the tank? | Water, plus a few millilitres of water-based fragrance | Undiluted fragrance oil and nothing else — 400ml |
| What is the carrier? | Water. The fragrance is dissolved in it and rides out with it | There is no carrier. The fragrance is the output |
| What does the output feel like? | A visible cool mist; surfaces close by can read slightly damp | A dry mist, generally invisible, leaving no film on glass or stone |
| Where do the droplets go? | They are relatively heavy and settle within a few feet | Nano-scale, so they stay suspended and travel with room air |
| What limits the reach? | Fragrance density — past a point, more oil separates instead of dispersing | Room volume and air exchange, not dilution |
| What else does it change in the room? | Humidity rises — 500ml of water over 16–18 hrs on a Sukoon | Nothing but fragrance. Identical behaviour in every season |
| What maintenance does it ask? | Refill water each run; descale and wipe the disc periodically | Refill 400ml at 90+ days a fill; wipe the housing |
| What fragrance does it take? | Water-based Hotel Collection only — never reed oil | Cold-air oil only — never water-based fragrance, never reed oil |
| How is it controlled? | Sukoon: remote, steady / 2H / 4H timers. Boond: onboard, night light | App plus onboard buttons, 1h / 4h / 8h / 24h, intensity, auto-stop, key-lock |
| The honest caveat: the row that costs you money is the fragrance row. The two oils share scent names and are entirely different formulations — the water-based Hotel Collection is built to disperse through a water tank and must never be put into a Vaayu, and the Vaayu's cold-air oil is not an ultrasonic fragrance. And SOSA does not currently sell a separate Vaayu refill oil at all; the 400ml in the box is the whole supply available today, where Hotel Collection refills for the ultrasonic machines are on sale from ₹299. If long-term supply is part of your decision, ask SOSA where the refill stands before you spend ₹11,999. | ||
Shop this guide
The two mechanisms, and what each one drinks
Sukoon · 270–320 sq ft₹1,899Shop → Hotel Collection · ultrasonic onlyfrom ₹299Shop → Vaayu · waterless, up to 1000m³₹11,999Shop →
The SOSA principle
An ultrasonic diffuses water with fragrance in it. A cold-air machine diffuses fragrance with nothing in it.
Every difference in reach, in feel, in seasonal behaviour and in price is a consequence of that one line. Nothing else about the two machines needs remembering.
Part three — when dilution is the feature rather than the flaw
I have spent two sections explaining why water limits an ultrasonic, so let me now argue the other side properly, because for the great majority of Indian rooms the ultrasonic mechanism is the right one and the cold-air mechanism is overkill. Dilution is what makes an ultrasonic gentle. A machine whose output is mostly water cannot easily overwhelm a bedroom, which matters if you are scenting a space where somebody sleeps, or a small flat, or a room used by people with different tolerances. A cold-air machine at high intensity in a 200 sq ft bedroom is simply too much instrument for the job, and the fix — turning the intensity down and the timer short — means paying ₹11,999 to use a fraction of what you bought.
Dilution is also what makes an ultrasonic cheap to run, and this is where the comparison genuinely favours the ₹1,899 machine. A 15ml Hotel Collection bottle at ₹299 doses many tank-fills, the 100ml is ₹999 and the 300ml is ₹1,799, and the other ingredient is tap water. That supply exists, is on sale today, and can be planned around for years. The Vaayu's position is the opposite: the machine is superb and the oil situation is unfinished, because no separate cold-air refill is currently sold. I would rather write that sentence in every comparison than let a reader discover it after they have committed. Write to SOSA and ask before you buy if you are planning past the first 400ml.
And the case where neither machine is the answer: if what you want is a constant low background in one room and you never want to think about it, a reed diffuser at ₹749–₹849 for 50ml or ₹1,249–₹1,349 for 130ml does that with no socket, no tank and no noise, and goes on doing it through a power cut. Machines exist for two things a reed cannot do — filling a space on demand, and covering a volume larger than a point source can reach. If you need neither, do not buy either machine. The one product I would steer you away from as a coverage answer is the Megh: at ₹3,499 with six litres and roughly 100 hours of runtime it looks like the big one, but it covers about 215 sq ft, less than the Sukoon at ₹1,899. It buys you runtime and humidity. It does not buy you a larger room.
Water is what makes an ultrasonic gentle, cheap and short-range. All three at once — you cannot keep two and drop the third.
— Sonal Sahani, SOSA
Part four — matching the mechanism to the room
The same four machines, arranged by the question the mechanism answers rather than by price. The last column is the one to read twice.
Mechanism to room
Which process suits which space, and what each adds to the air
| Machine | Mechanism | Coverage | What it adds besides fragrance | Price |
|---|---|---|---|---|
| Sukoon ★ | Ultrasonic · 500ml water tank | 270–320 sq ft, 16–18 hrs on low | Moisture — welcome in a dry winter, less so in a coastal August | ₹1,899 |
| Boond | Ultrasonic · 300ml, USB | ~150 sq ft, ~6 hrs a fill | Moisture, plus a colour night light | ₹899 |
| Megh | Ultrasonic · 6L, ~100 hrs runtime | ~215 sq ft — less than the Sukoon | A great deal of moisture. This is what it is for | ₹3,499 |
| Vaayu | Cold-air nebulisation · 400ml neat oil | Up to 1000m³ ≈ 2,000–3,000 sq ft | Nothing. No water, no heat, no residue | ₹11,999 |
| Reed diffuser | Passive evaporation off six fibre reeds | One room, honest ceiling near 250–300 sq ft | Nothing, and no electricity either | From ₹749 |
Honest notes for buyers: coverage figures are manufacturer specifications and move with ceiling height, ventilation, doors and season; 1000m³ translated to floor area is arithmetic on that specification, not a measurement in your home. The Vaayu is ₹11,999 (the product page shows a rounded ₹12,000): waterless cold-air nebulisation, 400ml refillable tank at 90+ days a fill, Bluetooth app plus onboard buttons, 1h / 4h / 8h / 24h timers, adjustable intensity, auto-stop, key-lock, under 38 dB, DC 12V / 1A at 5W, 0.9 kg, freestanding or wall and HVAC mount, CE, RoHS and SGS certified, shipping with four Hotel Collection fragrances at 100ml each. SOSA does not currently sell a separate Vaayu refill oil; confirm availability with SOSA before purchase if long-term supply matters. The water-based Hotel Collection (15ml ₹299 · 100ml ₹999 · 300ml ₹1,799) is for ultrasonic machines and is not a Vaayu refill despite the shared scent names; reed oil goes in neither machine. Warranty, AMC, installation and spare-part terms are not confirmed here — ask SOSA. Nothing on this page claims any effect on health, mood, sleep, focus, air purification or odour removal; both machines add fragrance to air rather than cleaning it, so ventilate before you scent. Keep fragrance away from children and pets.
What an ultrasonic machine drinks
SOSA Hotel Collection · water-based, for ultrasonic machines ₹299 / 15ml
Hotel-inspired compositions formulated to disperse through a water tank — which is exactly why they belong in a Sukoon, a Boond or a Megh and nowhere else. 15ml ₹299, 100ml ₹999, 300ml ₹1,799. Please read the boundary carefully: this is not a Vaayu refill. The Vaayu runs an undiluted cold-air oil and the two formulations share scent names but nothing else. Reed oil, equally, never goes into any machine. Three separate systems, three separate oils, and mixing them is the single most common and most expensive mistake in the category.
SS
ISIPCA
Versailles
Versailles
A note from Sonal
The question in this title arrives in my inbox more than any other machine question, and it is almost always asked as though one answer will be revealed as the good one. I have never been able to answer it that way, because the two mechanisms are not competing — they are sized differently. Asking whether cold-air is better than ultrasonic is a little like asking whether a kettle is better than a boiler.
What I do think is worth insisting on is the water. A great many readers on the coast bought an ultrasonic, ran it through one monsoon, found the room heavier than they liked and concluded the machine was faulty. It was not faulty. It was putting half a litre of water into their air every day, which is what it is designed to do and what a dry-winter buyer in Amritsar specifically wants. Knowing that in advance would have sent them to a different mechanism, or to a reed diffuser, and saved everyone the disappointment.
The last thing, and I would rather say it here than bury it: our cold-air machine is the better instrument on reach and the worse one on supply. There is no separate Vaayu refill oil on sale from us today. The ultrasonic side of the range has fragrance available from ₹299 and always will. If you are the kind of buyer who plans three years ahead, that asymmetry deserves a place in your decision, and a note to us asking where it stands. A portion of every order funds a girl's classroom through Nanhi Kali.
Frequently asked questions
Is a cold-air diffuser stronger than an ultrasonic diffuser?
Per unit of output, yes, and for a structural reason: an ultrasonic's mist is mostly water, so the fragrance in it is diluted, while a cold-air machine's output is undiluted oil. That is also why the coverage figures differ so widely — 270–320 sq ft for a Sukoon against up to 1000m³ for a Vaayu. In a small bedroom the extra density is not an advantage; it is simply more instrument than the room needs.
Does an ultrasonic diffuser make a room humid?
It adds water to the air, yes — that is the mechanism rather than a defect. A Sukoon empties 500ml over 16 to 18 hours on low; a Megh empties six litres across about 100 hours. Whether that is pleasant depends on where you live and the season. A cold-air machine adds none, which is the main reason coastal readers move across.
Can I put my Hotel Collection fragrance in a Vaayu?
No. The Hotel Collection is water-based and formulated to disperse in an ultrasonic tank; the Vaayu nebulises undiluted cold-air oil. They share scent names and are different products. Reed diffuser oil goes in neither machine. Three systems, three oils, no substitutions.
Which should I buy for a 400 sq ft open living-dining?
That size sits just past a single Sukoon's 270–320 sq ft and a long way below a Vaayu's range. In practice, either a Sukoon placed where the two zones meet, or a Sukoon plus a reed diffuser at the far end, will do it for well under ₹3,000. I would not spend ₹11,999 on a room that size, and I would not buy a Megh for it either, since it covers less than the Sukoon.
Do either of these purify the air or remove smells?
No, and I will not let that idea stand. Both machines add fragrance to air. Neither filters it, cleans it, kills anything in it or removes an existing smell — a scent laid over a smell simply produces a third one nobody designed. Open the windows, run the extractor, deal with the source, and scent afterwards.
Cold-air vs ultrasonic · 2026
Water with fragrance in it, or fragrance with nothing in it — that is the whole difference
Boond ₹899 for about 150 sq ft. Sukoon ₹1,899 for 270–320 sq ft with 16–18 hours on low, remote and timers, three 15ml fragrances in the box. Megh ₹3,499 for about 215 sq ft — runtime and humidity, never coverage. Vaayu ₹11,999, waterless cold-air, up to 1000m³, 400ml at 90+ days a fill, 5W, under 38 dB, timers and key-lock, with no separate refill oil currently sold. Water-based Hotel Collection from ₹299, for ultrasonic machines only. Free shipping above ₹499, and a portion of every order supports girl-child education through Nanhi Kali.
Sukoon ₹1,899 → Vaayu ₹11,999
Continue the read
More on machines and mechanisms
- Nebulising vs ultrasonic — what the word means, and how to test any seller's claim to it.
- Cold-air vs reed diffuser — active against passive, scored on eight axes.
- Sukoon vs Vaayu — ₹1,899 against ₹11,999, and why most homes should stop at the first.
- Which SOSA system for your room size — the range mapped to measured spaces.
- 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, explaining ultrasonic and cold-air nebulising diffusion as physical processes and what each implies for reach, humidity and fragrance supply. Machine specifications are manufacturer figures; coverage and runtime vary with intensity setting, ceiling height, ventilation and season, and any translation between volume and floor area on this page is arithmetic on those specifications rather than a measurement. No claim is made that either machine affects health, mood, sleep, air purity, or the removal of odours, or that scenting produces any commercial outcome.SOSA Vaayu specifications (verified from the live product page, August 2026): ₹11,999 (the product page displays a rounded ₹12,000). Waterless cold-air nebulisation — pressurised air atomises undiluted fragrance oil into a dry nano-mist; no water, no heat, residue-free. Coverage up to 1000m³, about 2,000–3,000 sq ft. 400ml refillable tank, 90+ days per fill at a mid intensity setting. Bluetooth app plus onboard buttons, 1h / 4h / 8h / 24h timers, adjustable mist intensity, auto-stop and key-lock. Under 38 dB. DC 12V / 1A, 5W. 165 × 80.5 × 215 mm, 0.9 kg, black or white. Freestanding or wall / HVAC mount. CE, RoHS and SGS certified. Ships with four SOSA Hotel Collection fragrances at 100ml each (400ml in total) in one of three combos chosen at checkout. SOSA does not currently sell a separate Vaayu refill oil; the 400ml supplied in the box is the fragrance available at the time of writing, and buyers who need long-term supply should confirm current refill availability with SOSA before purchasing. The cold-air oil supplied with the Vaayu is a different product from the water-based Hotel Collection sold for ultrasonic machines (15ml ₹299 · 100ml ₹999 · 300ml ₹1,799), which must not be used in a Vaayu despite sharing scent names. Other SOSA machines: Boond 300ml ₹899 (~150 sq ft) · Sukoon 500ml ₹1,899 (270–320 sq ft) · Megh 6L ₹3,499 (~215 sq ft — a runtime and humidity machine, not a coverage upgrade) · Aangan ₹25,999 (~8,000–10,000 sq ft) · Meenar ₹38,500 (12,000–18,000 sq ft) · Safar car diffuser ₹3,999. Reed diffusers 50ml ₹749–₹849 (6–8 weeks) · 130ml ₹1,249–₹1,349 (14–18 weeks) · duo sets ₹1,498–₹1,598 · oil-only refills 300ml ₹2,399 / 500ml ₹3,499. Runtime, consumption and coverage figures are manufacturer specifications and vary with intensity setting, run hours, ceiling height, ventilation and season; any per-month or per-day figure in this guide is arithmetic on those specifications, not a measurement. Electricity costs vary by state tariff. No claim is made that scenting affects ratings, reviews, bookings, occupancy, revenue, health, mood or air quality. 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.