An air purifier is a fan, a filter stack, a sensor array, and increasingly a WiFi module in a housing. The filter stack does the work: a pre-filter catches hair and coarse dust, a true HEPA layer (H13 or H14 grade, 99.97% capture at 0.3 microns) traps fine particulate matter, and an activated-carbon bed adsorbs volatile organic compounds and odours. Some designs add UV-C germicidal lamps or negative-ion generators, though the better engineers debate whether the ozone by-products of ionisation outweigh the benefit — at least one major PRD manufacturer publicly avoids UV-C on those grounds.
Foshan’s Shunde District has been called China’s Home Appliance City for decades. Over 3,000 appliance enterprises clustered around Midea and Galanz built the injection-moulding, motor-winding, and mould-tooling supply base that air-purifier ODMs now draw on directly. Shenzhen adds the electronics layer: PM2.5 and VOC sensor modules, Bluetooth and WiFi connectivity, Tuya IoT integration, and the rapid-prototyping infrastructure of Huaqiangbei. Guangzhou’s Nansha District, though technically a separate municipality, functions as part of the same integrated logistics and port network, and hosts large full-stack ODMs like Olansi. The region offers vertical integration — filter media, injection-moulded housings, BLDC and AC motors, and final assembly can all be sourced within a 100-kilometre radius.
The business model has two revenue streams: the hardware sale and the recurring filter replacement. Nearly every ODM designs proprietary filter-cartridge geometries for each OEM client, because the downstream brand makes its margin on subscription filter sales, not the purifier itself. This is why a brand rarely shares a filter format with a competitor — the lock-in is by design, and the ODM tools a new filter mould for each programme. The factory sells the razor; the brand sells the blades.
CADR — Clean Air Delivery Rate — is the number Western buyers scrutinise most, and the better PRD factories now run in-house CADR testing labs rather than outsourcing to third parties. Post-COVID demand cooled from 2021–2022 peaks but stabilised around wildfire-smoke awareness, allergen management, and the built-in filter-replacement annuity that makes the category sticky once the hardware is placed.