A community sensor logged four hundred and sixty-nine days of Bali's breath before it fell silent. A single government monitor reports intermittently for 4.4 million residents. Since the first of April, seven tons of waste a day have been pulled from Denpasar's rivers. The smoke in the alleys rises without an instrument to record it. The science underneath, the practical mask guide, what would actually help, in the order it should be deployed — and now, ninety days into the burn season, the first full data review: what the network actually recorded.