Technical Note
How the system is sized, installed, serviced and guaranteed. A whole-home air purifier — technically a positive-pressure fresh air system — filtering outdoor air into every room, so PM2.5 stays low and CO₂ doesn’t build up. The plain answers, before you decide.
Sizing · filtration · civil work · thermal load · service · guarantees. September 2026 edition.
System sizing and airflow
How one unit is sized to your home
Send us your carpet area and ceiling height and we return the figure for your home. The method: air changes per hour = effective airflow ÷ internal volume, where volume is carpet area × ceiling height.
| Carpet area | At 9 ft ceiling | At 10 ft ceiling |
|---|---|---|
| 1,000 sq ft | full air change ~30 min | ~34 min |
| 1,500 sq ft | ~46 min | ~51 min |
| 2,000 sq ft | ~60 min | ~68 min |
Theoretical vs practical. Those figures are computed for a sealed volume. A lived-in home is not sealed — doors open, cooking happens, balconies are used. Plan on roughly 50% of the theoretical rate: a 30-minute air change on paper behaves closer to an hour in practice.
One unit is specified to 2,000 sq ft carpet. Beyond that, or across more than one floor, we specify two. Two units on separate floors outperform one larger unit, because pressure does not distribute through a stairwell.
Rated versus effective airflow
| Basis | Figure |
|---|---|
| Rated (free-air) | ~700 m³/h |
| Effective in service | ~500 m³/h |
| Fan | EC, variable speed |
All our sizing uses the effective figure. Filters impose static pressure, and the free-air rating is achieved only with no filters fitted. Free-air ratings are the norm in quotations, so it is worth checking on which basis any competing CFM figure is stated.
How filtered air reaches closed rooms without ducting into each one
By pressure, not ducting. The unit supplies more air than leaks out, holding the home slightly above outdoor pressure. Air moves down that gradient into every room through door undercuts and ordinary gaps, and leaves through bathroom and kitchen shafts.
Two qualifications. It relies on a door undercut of roughly 10–12 mm, standard in most homes — a room with a full threshold seal will lag. And distribution is not uniform: rooms nearer the unit respond faster, and the farthest rooms take longer to settle.
Bathrooms sit on the exhaust side of that path — where air leaves, not a supply target. Bathroom air is never pushed back into bedrooms.
Indoor benchmarks, windows and doors shut
| Measure | Target |
|---|---|
| PM2.5, fresh filters | under 10 µg/m³ |
| PM2.5, sustained across the filter cycle | under 15 µg/m³ |
| CO₂, continuous | under 1,000 ppm |
We hold below 15 µg/m³ across the whole filter cycle, not only after a filter change.
Windows and doors shut is the design condition — the system is the ventilation. It is also why CO₂ matters: a closed bedroom with two adults and no fresh-air supply typically reaches 1,200–2,500 ppm by morning. A single-room recirculating air purifier cannot reduce that figure at any price, having no outdoor air path.
Filtration and consumables
The filtration sequence
- Stage 1 — washable pre-filter. Dust, lint, insects. User-cleanable, pulls out like an AC filter.
- Stage 2 — H13 HEPA. The primary particulate stage. H13 removes ≥99.95% of particles at the most-penetrating size, around 0.3 µm.
H13 is standard across every installation. We do not vary the grade between units. Each unit carries three H13 panels at 362 × 276 × 50 mm, replaced on rotation — one panel per service visit. Rotation is what keeps delivered airflow steady: panels are always at staggered stages of their life, so the resistance the fan works against stays roughly constant instead of climbing to a peak and dropping after a change.
How often filters are cleaned or replaced
| Item | Interval |
|---|---|
| Pre-filter — rinse or vacuum, 2-minute DIY | every 7–10 days |
| H13 HEPA — winter | every ~45 days |
| H13 HEPA — summer | every ~60 days |
The washable pre-filter protects that cadence, taking the dust and lint load so the HEPA stays on schedule through a Delhi winter.
Civil work, installation and aesthetics
What is needed on site
- One 10-inch circular opening — core-cut through the wall, a cut in window glass, or a cut in a wooden ply panel
- One 6A power point near the unit
- A wall bracket for the outdoor unit
That is the complete list. No internal ducting to individual rooms, no false ceiling, no floor space given up indoors.
What is included in the installed price, and what is not
Included: the core cut, glass cut or ply cut; louvre/grille; ducting; electrical connection; wall bracket; and weather sealing (silicone and closed-cell foam). Vibration mounts are not required — the unit is bracket-mounted and does not transmit vibration into the structure.
Not included:
- A rain cowl or external cover. Where the mounting position is exposed we ask you to arrange one, and will advise on what is needed at the survey.
- Toughened glass. An ordinary pane we cut ourselves, covered by the price. Toughened glass cannot be cut after tempering and must be re-made at a specialist’s factory setting — through your own vendor, typically ₹5,000–8,000 depending on clear or reflective glass. We can connect you. We raise this before quoting rather than after.
Where the outdoor intake goes, and how it is protected
Placement is decided at the site survey. The rules: away from kitchen exhausts, bathroom shafts, DG-set exhausts, basement parking vents, and the building’s own extract points. We do not mount on a kitchen-exhaust wall.
For rain, the louvre is downward-angled and the intake set above the local splash line.
On birds: the washable pre-filter is specified with this in mind — feathers, nesting debris and airborne matter are caught at the first stage, before the HEPA. Physical nesting on the body of the unit is a housekeeping matter at your end, as with any outdoor equipment on the façade.
This is the reason we survey before quoting. A whole-home system drawing air from the wrong façade will faithfully deliver filtered exhaust fumes into the home.
What you see indoors
There is no internal unit. The machine sits entirely outdoors — 14″ W × 17″ H × 20″ D. Indoors you see a single grille where the duct terminates. No visible duct runs indoors, and no floor or shelf space is used.
Thermal impact, noise and power
Effect on room temperature, and on ACs and heaters
Yes, they will work harder. You are bringing outdoor air in continuously, so at 45°C or at 5°C there is a real added load. Any fresh-air system carries it.
Customer experience is more useful here than theory. Summer has not come up as a problem — hotter incoming air or AC load has not been raised with us. In winter, a heater can be fitted to the unit on request, lifting incoming air by 4–5°C, in preference to running an oil heater of your own.
Beyond that it is a matter of setting. The fan is variable speed; most homes settle at a moderate setting year-round and lift it on peak-AQI days. Through temperature extremes you can run it lower, trading air-change interval against thermal load.
Noise
We do not publish a measured dB curve. At normal running — around 5V, where these sit almost all the time — the unit is effectively inaudible indoors. There is no hum to live with.
Two reasons it is quieter than expected. The fan is outdoors, so fan noise stays outside the building envelope. And an EC fan at a low duty point is genuinely quiet — noise becomes a consideration only well above the speeds a home runs at.
Power draw, and running on an inverter
| Measure | Figure |
|---|---|
| Normal operating draw | ~30 W |
| Running cost, continuous, at ₹8/unit | under ₹170/month |
Maximum fan speed is seldom reached in practice. ~30 W is the figure that matters for sizing backup. At roughly 30 W this is comparable to a single ceiling fan and runs on any standard domestic inverter with no meaningful effect on backup duration. Being an EC fan, consumption scales smoothly with speed rather than cycling on and off, so on backup you can simply run it lower.
AMC, warranty and service
What the AMC covers
The AMC is optional and priced separately from the system. Filters are included, not labour-only: every scheduled visit covers filter replacement and a full machine clean. Unscheduled fault visits are also covered.
Cadence follows pollution load rather than the calendar: roughly every 45 days through winter and every 60 days through summer, set so indoor numbers stay in specification through the season that tests them. Each visit replaces one of the three H13 panels on rotation.
The aqi0 air-quality monitor is available separately at ₹4,000.
Warranty
| Component | Cover |
|---|---|
| Fan motor — no-questions replacement | 1 year |
| Fan rated life | 40,000 hours ≈ 4.5 years continuous |
| Speed controller / electronics | 3 years |
| Sheet-metal chassis | no warranty |
The chassis is a powder-coated sheet-metal enclosure mounted outdoors. We do not warrant it against weathering over time.
Testing, our commitment and moving home
Measured before and after
Indoor and outdoor PM2.5 are measured at the site survey as a pre-installation baseline, and again at commissioning. Both readings are recorded against your installation in our system.
A commissioning reading is one measurement on one day. Where an aqi0 monitor is installed, it gives continuous logged PM2.5 and AQI in your home, so performance can be reviewed across the whole winter rather than at a single point.
Our commitment, and what we cannot promise
What we commit to. In steady state — the home sealed as designed, filters current — the system holds PM2.5 under 10 µg/m³ with fresh filters and under 15 µg/m³ sustained across the filter cycle, and CO₂ under 1,000 ppm.
What we cannot promise. This is a positive-pressure system: it works by holding the home slightly above outdoor pressure, and that pressure is what keeps polluted air out. Where the envelope does not hold, the mechanism does not either:
- External windows or doors left open — pressure is lost and outdoor air enters directly
- Windows or doors that leak badly — old or poorly sealed frames bleed pressure continuously
- An open kitchen without the exhaust running — cooking is itself a major indoor PM2.5 source
- Carpet area above 2,000 sq ft on a single unit
On everyday living. Doors open, people come in, food is cooked. Each briefly mixes outdoor air into the room and produces short spikes. The system pulls the level back down and holds it, which is why the commitment is written against the sustained average rather than instantaneous readings.
Remedy. Where those conditions are met and the system does not perform, we rectify at our cost — filters, servicing, adjustment to the installation, or replacement of the unit if the fault is ours. Verification is against logged monitor readings where an aqi0 monitor is installed, and against our commissioning measurements otherwise.
If you move home
We do not charge for the shift itself — removing the machine and setting it up at the new address is included. You bear the civil work at both ends: making good at the old home (replacing the glass panel or sealing the core cut) and creating the opening at the new one. These are third-party civil costs and vary with what the two buildings require.
Frequently asked questions
What size home does one unit cover?
Up to 2,000 sq ft carpet area. Beyond that, or across more than one floor, we specify two units. Two units on separate floors outperform one larger unit, because pressure does not distribute through a stairwell.
How does filtered air reach closed bedrooms without ducting into each room?
By pressure, not ducting. The unit holds the home slightly above outdoor pressure, and air moves down that gradient through door undercuts into every room, leaving through bathroom and kitchen shafts. It relies on a door undercut of roughly 10–12 mm, which is standard in most homes.
Will my AC or heater work harder?
Yes. You are bringing outdoor air in continuously, so at 45°C or 5°C there is a real added load — any fresh-air system carries it. In practice summer has not come up as a problem with customers. In winter a heater can be fitted to the unit on request, lifting incoming air by 4–5°C.
How loud is it?
Effectively inaudible indoors at normal running. The fan sits outdoors, so fan noise stays outside the building envelope, and an EC fan at a low duty point is genuinely quiet. We do not publish a measured dB curve.
What civil work is needed?
One 10-inch circular opening (core-cut through the wall, or a cut in window glass or a ply panel), one 6A power point near the unit, and a wall bracket. No internal ducting to individual rooms, no false ceiling, no indoor floor space.
Is toughened glass included?
No. An ordinary pane we cut ourselves and it is covered by the price. Toughened glass cannot be cut after tempering and must be re-made at a specialist’s factory setting through your own vendor, typically ₹5,000–8,000 depending on clear or reflective glass. We raise this before quoting rather than after.
What does the warranty cover?
The fan motor carries a 1-year no-questions replacement, and the speed controller and electronics are covered for 3 years. The fan is rated for 40,000 hours, about 4.5 years of continuous running. The powder-coated sheet-metal chassis is mounted outdoors and is not warranted against weathering.
What happens if the system does not perform?
Where the home is sealed as designed and filters are current, we rectify at our cost — filters, servicing, adjustment to the installation, or replacement of the unit if the fault is ours. Verification is against logged monitor readings where an aqi0 monitor is installed, and against our commissioning measurements otherwise.
Can the system be moved if I change homes?
Yes, and we do not charge for the shift itself — removing the machine and setting it up at the new address is included. You bear the civil work at both ends, which is third-party cost and varies with what the two buildings require.