Bali's projected 2025 population is 4.46 million. The single KLHK reference-grade PM2.5 monitor indexed for the island on the national ISPU portal has reported intermittently through the year, and has been quiet for several months — leaving community sensors carrying most of the public record in the meantime.
Bali's projected 2025 population, according to BPS Statistics Indonesia, is 4.46 million. The number of KLHK reference-grade PM2.5 monitors indexed for the island on the national ISPU portal is one — the Denpasar Lumintang station on Jalan Mulawarman. It reported sporadically through 2025 and, as of the first quarter of 2026, has been quiet on the portal for several months.
Jakarta, for comparison, operates 10 reference-grade sensors and some 110 low-cost community monitors through its DKI programme, according to the 2024 Indonesia Air Quality report from the Centre for Research on Energy and Clean Air. Hong Kong runs 18 fixed stations for 7.5 million residents; London more than 100 continuous sites on its Local Air Quality Network. Bangkok's PCD runs 70 standard stations.
On a per-capita basis — government reference-grade sensors per million residents — Bali runs at roughly 0.2. Jakarta at 11. London at 11. Hong Kong at 2.4. Bangkok at about 4.5.
The CREA report, summarising provincial coverage outside of Jakarta, described "a significant coverage gap beyond the city limits into other satellite cities." Bali fits naturally within that frame. The Denpasar Lumintang station is itself a credit to the people who run it: it is operated by the Environmental Laboratory Unit of the city's Environmental Health and Cleanliness Service under the national ISPUNet programme, and when it is online it publishes hourly AQI and 24-hour PM2.5 readings in the standard international format.
Community sensors (AQICN, Nafas, AirGradient, PurpleAir) and reference-grade government instruments are not really substitutes for each other — they are complements. A reference-grade network, when fully online and openly published, adds calibration discipline and an authoritative public archive against which community readings can be cross-checked. The two are stronger together than either alone.
| City / province | Population | Gov. reference sensors | Per million |
|---|---|---|---|
| Jakarta DKI | ~10.6 m | 10 reference + 110 low-cost | 11.0 |
| London | ~9.0 m | 100+ LAQN continuous | 11.1 |
| Bangkok | ~15.5 m metro | 70 PCD standard | 4.5 |
| Hong Kong | ~7.5 m | 18 EPD fixed | 2.4 |
| Bali | 4.46 m (BPS 2025) | 1 KLHK ISPU — not reporting | 0.2 |
Reference-grade government instruments only. Community and private sensors (AQICN, Nafas, AirGradient, PurpleAir) are not included. Sources in the footer of this dispatch.
"A significant coverage gap beyond the city limits into other satellite cities."Centre for Research on Energy and Clean Air · Indonesia Air Quality 2024
When the Denpasar Lumintang instrument is reporting, its readings appear on the portal in the standard international format. When it is offline, the island's official record pauses with it. The community data, as Dispatch I set out, has carried the long-running public record in the meantime — an imperfect but informative stand-in.
A practical wishlist — one that appears in CREA's recommendations and in the public submissions of several local researchers — would add a handful of reference-grade monitors at population centres including Denpasar, Ubud, Canggu, Seminyak, Nusa Dua and either Singaraja or Amed; an hourly ISPU dashboard with a clean CSV backlog open to researchers; and an annual uptime report on the London LAQN model. By the standards of the equipment involved, none of these items is large or expensive.
The next dispatch turns to what has happened on the ground since the first of April.