Technical Note

How the system is sized, installed, serviced and guaranteed. A whole-home air purifier — technically a positive-pressure fresh air system — supplying filtered outdoor air through an installation assessed for the home. The plain answers, before you decide.

Sizing · filtration · civil work · thermal load · service · guarantees. September 2026 edition.

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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.

Theoretical vs practical. Those figures are computed for a sealed volume at 500 m³/h. A lived-in home is not sealed — the main door opens, cooking happens, balconies are used — so plan on roughly 50% of the theoretical rate: a 30-minute air change on paper behaves closer to an hour in practice. Treat that as a planning rule of thumb, not a measurement. Real rooms also mix unevenly, and duct resistance, filter loading, fan speed and how the rooms connect all move the result, so one nominal air change does not mean every part of the home has been cleared.

One unit is specified to 2,000 sq ft carpet. Beyond that, or across more than one floor, we specify two. Separate floors and rooms need suitable supply and exit paths; we’ll confirm the distribution plan with you.

Rated versus effective airflow

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

The supply can create a small pressure difference that encourages air movement through available room connections and exit paths. Distribution depends on the layout, openings and exhaust operation; it is checked rather than assumed to be identical in every room.

Door undercuts and transfer paths matter. The design commonly allows around 10–12 mm of undercut, but this is not a universal instruction to modify a door. Full threshold seals and fire-rated doors need appropriate assessment. Rooms farther from the supply may respond differently.

Bathrooms should remain on the extract side of the design. The installation must account for their exhaust and replacement air; positive pressure alone does not guarantee that air can never flow back towards occupied rooms.

Indoor benchmarks, windows and doors shut

We hold below 15 µg/m³ across the whole filter cycle, not only after a filter change.

External windows and doors shut is the design condition. Bedroom CO₂ depends on occupancy and delivered outdoor air; a room HEPA purifier does not add outdoor air. An appropriate separate CO₂ instrument is needed to assess ventilation—the optional aqi0 monitor measures AQI and PM2.5.

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, Japanese media. The primary particulate stage. Three panels of 50 mm sit in series — 150 mm of media depth, roughly 6 m² of pleated area, about twenty times the face area. H13 classification specifies at least 99.95% integral efficiency at the most-penetrating particle size; that size is not a universal 0.3 µm cutoff.
• Optional — activated carbon. A carbon stage is available as an add-on at ₹2,200, refreshed about every six months and not covered by the care plan. It is worth being precise about what it does: carbon sits at the intake, so it adsorbs gases and odours in the air being drawn in — a neighbour’s cooking, traffic, a nearby exhaust outlet. It cannot remove VOCs generated inside the home, because the unit supplies air rather than recirculating it; those are reduced by dilution and by removing the source.

H13 is the specified grade. Each unit carries three panels at 362 × 276 × 50 mm, replaced on rotation—one panel per service visit. Rotation spreads replacements through the maintenance cycle; actual airflow still depends on loading, speed and the installation.

How often filters are cleaned or replaced

The washable pre-filter reduces the coarse load reaching the H13 stage. Inspect and service the system for actual conditions; heavy pollution can affect loading. Let washed parts dry before refitting and do not wash the H13 panels.

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

These are the standard provisions. We also confirm structure, permission, mounting, service access, weather protection and the visible duct route with you. No HVAC integration is offered.

What is included in the installed price, and what is not

Included: the core cut, glass cut or ply cut; diffuser; ducting; electrical connection; wall bracket; and weather sealing (silicone and closed-cell foam). Mounting and any vibration-control needs are assessed at the site.

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.
• 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 confirmed with you before installation. 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 confirm the intake position with you before quoting. Particle filtration does not establish removal of exhaust gases, so avoiding contaminated intake positions matters.

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 diffuser where the duct terminates. The visible duct route and finish are agreed for the property; the outdoor unit does not occupy indoor floor or shelf space.

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.

The added temperature and humidity load depends on outdoor conditions and supply volume. Cooling or heating capacity must be assessed rather than assumed adequate. The published on-request winter heater option is discussed separately, including its suitability and energy requirements; no fixed temperature rise is guaranteed for every operating condition.

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. Sound depends on fan setting, mounting, duct route and the room. Discuss noise-sensitive areas at the assessment and check the proposed operating setting.

Locating the fan outdoors changes where sound is produced, but does not guarantee inaudibility indoors or at neighbouring properties.

Power draw, and running on an inverter

At constant 30 W, continuous operation uses 21.6 kWh in 30 days. Actual draw and electricity cost vary with settings and tariff; added cooling or heating energy is separate. Confirm inverter compatibility, capacity and runtime rather than assuming there is no effect on backup duration.

AMC, warranty and service

What the annual care plan (AMC) covers

The annual care plan is priced separately from the system; without it, filters are ₹2,200 each and you can change them yourself in minutes. 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: every ~45 days through the October–February peak, and at longer intervals through the rest of the year, 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 care plan price does not rise on renewal. A customer who signs at ₹14,750 renews at ₹14,750; we do not reprice a plan because the system is already bought. Two years taken together are about 16% below the annual rate, and a plan signed with the system carries 75 days on top, so a 365-day plan runs 440 days and a two-year plan runs 805. Beyond that, renewals move in line with inflation rather than in steps, and the two-year option remains available at every renewal.

The aqi0 air-quality monitor is available separately at ₹4,000, and the aqi0 Dial — a Wi-Fi remote control paired with the same app — at ₹7,500.

Warranty

The fan carries one year from installation in all cases. Years two to five apply only if the care plan has never lapsed — renewed unbroken, the cover continues to a maximum of five years; if the plan lapses, cover reverts to that standard first year. Within warranty we repair the fan, or replace it with an equivalent unit — which may be new or refurbished. Rated life is a manufacturer’s figure, not the warranty period and not a prediction of the date a fan will fail.

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 PM2.5 is measured at installation — before the system is switched on, 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. The main door opens, 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 shift the unit for you — removing it and reinstalling it at the new address. Two civil costs sit with you: restoring the old home (changing the glass back or filling the core cut), which you arrange at your end; and a nominal civil charge for the new opening at the new address, which we handle. Ask us for a shifting quote when the time comes — we set both out before the move.

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. Separate floors and rooms need suitable supply and exit paths; we’ll confirm the distribution plan with you.

How does filtered air reach closed bedrooms without ducting into each room?

Air uses available transfer and exit paths, which must be assessed for the home. Door undercuts can support distribution; fully sealed or fire-rated doors need particular attention. The installation must also account for kitchen and bathroom exhaust.

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. Thermal and moisture loads need assessment. The on-request winter heater option requires confirmation for the installation and operating conditions.

How loud is it?

We do not publish a measured dB curve. Noise varies with speed, mounting, duct route and the room; discuss the intended setting and any noise-sensitive areas with us.

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. We’ll confirm mounting, service access and the visible duct route with you; the unit sits outdoors.

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 is covered for as long as the machine stays on a care plan, up to five years; without a plan the cover is one year from installation. Within warranty we repair it or replace it with an equivalent unit, new or refurbished. 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. We shift the unit — removing it and reinstalling it at the new address. You cover the civil work to restore the old home (changing the glass back or filling the core cut), and a nominal civil charge covers the new opening. Ask us for a shifting quote when the time comes.

Further reading

H13 filter classification · Particle filtration and its limits · Bedroom ventilation measurement