About this tool
This page gathers the latest air-quality reading for every Cambodian city this site covers — Phnom Penh, Siem Reap, Kandal, Battambang and Kampot — onto one screen, using the same AQI scale and pollutant table as the dedicated city pages. It is built for people who want the national picture at a glance: residents deciding whether today is an outdoor day, parents and schools planning activities, and anyone trying to work out why the number here differs from the one in another app. Two honest limits matter more than anything else here. Coverage is a handful of monitoring points, not a map of the country — if you live in a province with no monitoring station, the closest covered city's reading is all there is, and it is only an approximation of the air where you actually are. And each card is one location's latest reading, not a city-wide average. "Live" means the freshest value the upstream currently holds, not a minute-by-minute feed. Each city has its own page, linked from its card, and the weather pages for the same cities sit alongside in the tools directory.
How it works
When you open the page, your browser asks the InKhmer API for the Cambodia overview, which in turn asks azwebdata — the platform's shared data service — for the latest air-quality reading of each configured city. Azwebdata keeps snapshots of Cambodian air quality: a worker refreshes them on a thirty-minute schedule, and locations outside the scheduled set are fetched on demand and held in a fifteen-minute cache. The upstream is OpenAQ, which publishes raw pollutant concentrations in micrograms per cubic metre (μg/m³) from real monitoring locations; when OpenAQ has no matching station, OpenWeatherMap's modelled air-pollution values are used instead. The AQI number is on the US EPA scale. For OpenAQ readings it is derived from the PM2.5 concentration — falling back to PM10 — through the EPA breakpoint table, so PM2.5 drives nearly every Cambodian AQI on this page. If the feed fails, the last good cached value is served; if nothing is available, the page shows a "no data" message rather than inventing a reading.
Use cases
- A parent in Phnom Penh checking the current AQI band before letting children play outside in the morning.
- A runner or cyclist in Siem Reap deciding whether dry-season haze makes today an indoor-training day.
- A school or NGO in Kandal reviewing the pollution level before scheduling an outdoor event for students.
- A resident of a province with no monitor — Takeo, Kampong Speu, Kep — reading the nearest covered city as a rough guide.
- A reader comparing this site’s number with another weather or air-quality app and wanting to know which scale and station produced it.
- Someone in a sensitive group using the published AQI band guidance to plan how much outdoor exertion to take on.
- A traveller moving between Phnom Penh, Battambang and Kampot comparing the three cards before setting off.
Frequently asked questions
Is this the official Cambodian government air-quality reading?
No. Cambodia’s Ministry of Environment runs its own monitoring programme and has published readings on its own channels. This page is independent: it serves OpenAQ monitoring data — with OpenWeatherMap as fallback — collected through the azwebdata service. Use it as a convenient public reading, not as a government bulletin; for official announcements, refer to the Ministry of Environment.
Why does the AQI here differ from what another app shows?
Usually one of three reasons: the station, the scale, or the timing. Different apps read different monitoring locations, and a single station is not a city average. The same PM2.5 concentration also produces different numbers on different AQI scales — this page uses the US EPA bands — and averaging windows differ too: a latest-value reading, a 24-hour average and a NowCast figure are three different things.
What does the AQI number actually mean?
AQI — the Air Quality Index — compresses pollutant concentrations into a single number on the US EPA scale, which runs from 0 to 500 in six named bands: Good (0–50), Moderate (51–100), Unhealthy for Sensitive Groups (101–150), Unhealthy (151–200), Very Unhealthy (201–300) and Hazardous (above 300). The full band table, with the standard health and cautionary statements, is shown on this page below the readings.
I live in a province with no monitoring station — what am I seeing?
You are seeing the nearest covered city’s reading, which is an approximation, not a measurement of your air. Coverage on this page is five cities — Phnom Penh, Siem Reap, Kandal, Battambang and Kampot — each backed by one monitoring location. Rural air is often cleaner than a city station suggests, but during burning season smoke travels long distances; treat the nearest city as a directional guide only.
How often is the data refreshed?
Azwebdata’s scheduled worker pulls Cambodian air-quality data every thirty minutes, and locations outside the scheduled set are fetched on demand and cached for fifteen minutes — so the freshest value is normally under half an hour old. The page requests the latest values when you load it, sharing a one-hour cache key between requests. Each reading carries the time it was actually observed at the monitor.
What does the page show when a station is offline or the feed is stale?
It degrades quietly rather than breaking. If a provider stops answering, azwebdata serves the last good cached value for that location; a city with nothing available is simply left off the list; and if every city fails, the page shows "No air quality data at the moment" instead of an error. The "Updated" line shows when the displayed data was served.
Which pollutant drives the AQI shown for Cambodia?
PM2.5 — fine particles small enough to reach deep into the lungs — in almost every reading. The upstream publishes raw concentrations per pollutant, and this service derives the headline AQI from the PM2.5 value using the US EPA breakpoints, falling back to PM10 when no PM2.5 sensor reported. The pollutant table on each card still lists PM2.5, PM10, ozone, NO₂, SO₂ and CO individually.
Does this page forecast tomorrow’s air quality?
No. Everything shown is the most recent observation the upstream currently holds — a snapshot, not a forecast, and there is no prediction for tomorrow or next week. For planning, the useful honest guide is the seasonal pattern: PM2.5 in Cambodia is typically higher through the November-to-April dry season, when crop-residue and biomass burning peaks, and lower once the monsoon rains return.
Data and accuracy
Readings come through azwebdata, which polls OpenAQ — with OpenWeatherMap as fallback — on a thirty-minute schedule for its configured Cambodian locations and answers other location queries on demand through a fifteen-minute cache. Each card therefore shows one location's most recent stored value at its observation time — not a city-wide average, and not a forecast. When a provider is unreachable the last good cached value is served; when nothing exists for a city it is omitted, and if every city fails the page shows "No air quality data at the moment" rather than an error. AQI follows the US EPA bands in the table above; the seasonal remarks — higher PM2.5 through Cambodia's November-to-April dry season, when crop-residue burning peaks — are drawn from the cited studies, not measured by this site.
Sources
- OpenAQ — open air-quality data platform — OpenAQ
- OpenWeatherMap — Air Pollution API — OpenWeatherMap
- Air Quality Index (AQI) Basics — the US EPA bands — US EPA — AirNow
- Seasonal and diurnal variation of carbonaceous PM in Phnom Penh (Atmosphere 17(7):646) — MDPI — Atmosphere
- Air Quality Management in Cambodia (MoE presentation) — UNESCAP / Ministry of Environment Cambodia
Content last reviewed 19 October 2026