The ceiling is already the largest surface in the room.
A 20 nm doped anatase film that oxidises volatile organics on contact, driven by the light the room already has.
Schematic of the coated surface at molecular scale. Photons from the luminaire land on the titanium dioxide crystallites; while the coating is active each hit releases a hydroxyl radical that oxidises a nearby volatile organic molecule into carbon dioxide and water. Drag to orbit. Hover a molecule to name it.
Schematic · not to scaleWhat builds up in an occupied room
Organics accumulate wherever people spend a day in the same volume of air, and ventilation runs on a timetable rather than on a reading. The last figure below is included because this coating does nothing about it — TiO₂ acts on gases, and particulates need a filter.
Premature deaths a year from air pollution
WHO, ambient and household combined
PublishedTypical TVOC in an occupied classroom
Rises through the teaching day
PublishedTVOC at the end of a full day
Before the room is next ventilated
PublishedUrban PM2.5 — which this does not touch
5× the WHO 2021 annual guideline of 5 µg/m³
PublishedPhoton to CO₂, and what is observable
Three steps across fifteen orders of magnitude in time. Only the last one is measurable in a room; the first two are inferred from the absorption edge and the rate. Saying which is which is the difference between a mechanism and a diagram.
Charge separation
A photon at or below 430 nm lifts an electron across the gap and leaves a hole behind. Pristine anatase needs 388 nm — ultraviolet the room does not have. The dopant is what pulls the absorption edge into the blue end of ordinary lighting, and it is the whole reason this works off a ceiling fitting.
Inferred — the absorption edge is measured, the carriers are not.
Radical formation
The hole oxidises adsorbed water to a hydroxyl radical; the electron reduces oxygen to superoxide. Both need humidity, which is why the reference run is stated at 45% RH — below about 20% the rate falls off, and in a very dry room this surface is a much duller instrument.
Inferred — rate is measured, the radicals are not counted.
Oxidation at the surface
The radical breaks the organic apart at the point of contact. Nothing is captured, so nothing saturates — but nothing is drawn in either. Removal is limited by how much air reaches the surface, which is why the number that matters is per square metre of coating, not per gram of powder.
Measured — concentration decay in the reference room.
TiO₂ + hν (λ ≤ 430 nm) → e⁻ + h⁺ · h⁺ + H₂O → •OH · e⁻ + O₂ → O₂•⁻ · •OH + VOC → CO₂ + H₂O
Film, light, rate, life
Four numbers that constrain each other. The film has to be thin enough for a carrier to reach the surface, the light sets the photon budget, the rate follows from both, and the life is limited by dust rather than by chemistry.
20 nm
Doped anatase · sol-gel · 50 m²/g · 95% coverage uniformity per m²
Thin enough that the substrate colour still reads through it, and thin enough that a photogenerated carrier reaches the surface before it recombines. Above roughly 50 nm the extra material absorbs light without contributing to the surface reaction.
Bench≤ 430 nm
Doped edge ≈2.9 eV · pristine anatase 3.2 eV · reference 400 lux
At 400 lux a ceiling delivers roughly 1.4 W/m² of visible flux, of which about 0.1 W/m² falls in the usable band. That is a small budget, and it sets everything downstream — double the illuminance and the removal rate moves with it, until the surface runs out of air rather than photons.
Bench1.7 ×10⁻³
µmol·m⁻²·s⁻¹ for VOC · 6 ×10⁻⁵ for NO₂ · 400 lux, 45% RH
Both figures are back-calculated from the reference room rather than quoted from a flow-cell at laboratory photon flux, because a flow-cell number under a UV lamp would be an order of magnitude higher and would not predict anything about a corridor.
Bench10,000 h
5% activity loss under accelerated UV-A · no consumables
The failure mode is not saturation but fouling: dust and surface films block the light before the lattice itself degrades. In practice the service interval is a cleaning schedule, not a replacement one, and that is the honest comparison against a filter.
BenchWatch the room come down
An air monitor running the reference model at 1 Hz. Switch the coating off and the room climbs back toward its uncoated equilibrium; switch it on and it settles under the 400 ppb threshold. Simulated telemetry, not a live room.
Room air · 300 m³ · 100 m² coated
Loading air model, surface controls and sensor layout
What it removes, stated in full
Each figure below names its quantity, its unit, the conditions it was taken under, and how it was arrived at. Where a comparison is involved, the thing being compared against is named too.
Reference run
Bench- Volume
- 300 m³
- 100 m² floor × 3 m
- Coated area
- 100 m²
- Ceiling only
- Illuminance
- 400 lux
- Ordinary corridor lighting
- Conditions
- 23 °C · 45% RH
- Humidity matters; the rate falls off dry
- Duration
- 4 h
- Single continuous run
- TVOC
- 500 → 300 ppb
- −40%
- NO₂
- 40 → 26 µg/m³
- −35%
- Derived rate
- 1.7 ×10⁻³
- µmol·m⁻²·s⁻¹ for TVOC
One room, one set of conditions, stated once. Every rate and percentage elsewhere on this page is back-calculated from this run rather than quoted from a flow-cell under a UV lamp, because a flow-cell figure would be roughly an order of magnitude higher and would predict nothing about a corridor.
VOC removed over four hours
500 → 300 ppb · 300 m³ · 100 m² coated · 400 lux
BenchNO₂ removed over the same run
40 → 26 µg/m³, same room and conditions
BenchVOC removal rate, µmol·m⁻²·s⁻¹
Derived from the reference room, per m² of coated surface
BenchFan and filter power
A HEPA unit for the same room draws ≈120 W continuously
PublishedActivity lost after 10,000 h UV-A
Accelerated exposure; extrapolates to a 10-year service interval indoors
BenchCO₂e avoided per 1,000 m²/yr
10.5 MWh of avoided purifier load at 0.60 t CO₂e/MWh
ModelledHours a day above the 400 ppb ventilation threshold
One 300 m³ teaching room across a modelled day, same occupancy either way. This is the number a facilities team can act on — a percentage removal hides it.
Above threshold for most of the working day
Crosses back under during the afternoon
Durability: 10,000 h accelerated UV-A exposure · 5% activity lost · extrapolated to a 10-year service interval at indoor light levels · monitoring at one node per 25 m², 1 Hz, alerting at 400 ppb.
Where a slow surface is the right answer
This is not a machine you point at a spike. It is a continuous floor under a room that is otherwise left alone for hours, which makes the fit fairly narrow and worth stating.
- Lecture halls and libraries where TVOC climbs through the day and ventilation is on a fixed schedule
- Corridors and circulation space that are already lit around the clock and have no air handling of their own
- Retrofits where the blocker is the fan energy and filter waste of a gas-phase unit, not the capital cost
What researchers ask first
01What does SABZPOOST remove, and what does it not?
It oxidises volatile organic compounds and, more slowly, nitrogen dioxide. In our reference room it took TVOC from 500 to 300 ppb over four hours and NO₂ from 40 to 26 µg/m³. It does nothing for particulate matter — TiO₂ acts on gases at the surface, and PM2.5 needs a filter. If particulates are your problem, this is the wrong product and we will say so.
02Does it need ultraviolet light?
No, and that distinction is the whole design. Pristine anatase has a 3.2 eV gap and needs 388 nm to activate — ultraviolet that interior lighting does not provide. Doping extends the absorption edge to roughly 2.9 eV, or 430 nm, which sits inside the blue content of ordinary fittings. The reference figures are stated at 400 lux, a normally lit corridor.
03How fast is it, really?
Slow, and deliberately quoted that way: about 1.7 × 10⁻³ µmol·m⁻²·s⁻¹ for VOC at 400 lux. A photocatalytic surface is not a substitute for opening a window during a spike. It is a continuous floor under the concentration in a room that is otherwise left alone for hours at a time.
04What maintenance does it need?
Cleaning, not replacement. There is no filter media and no adsorbent to regenerate, so there is no saturation point and no waste stream. Accelerated exposure shows about 5% activity loss after 10,000 hours of UV-A, which extrapolates to a ten-year service interval at indoor light levels — an extrapolation, not a ten-year field observation.
Give us a room and we will give you a curve
Tell us the volume, the illuminance at the surface, the coated area you could realistically reach, and roughly how many people are in it. We will run the same model against those numbers and send back the decay curve, including the cases where it is not worth doing.