The Minimum Airflow Particle Counter (MAPC) is a portable, low-power, low-cost, wireless optical counter which has been specifically designed for ultra-low-maintenance operation in heavily polluted environments. When exposed continuously to air with high particulate matter concentrations, the primary mode of failure for particle counters is a build-up of dust within the instrument. The MAPC circumvents this failure mode by severely restricting airflow through the system, enabling an estimated 5-year maintenance cycle. Such a long operational lifetime makes this instrument particularly suitable for IOT applications such as environmental air quality monitoring and pollutant source attribution using spatially distributed wireless sensor networks. Here, we present the theory of operation, instrument design, and collected data from a two-month field deployment in Beijing. We find that the MAPC performs comparably to other low-cost optical counters, but with a significantly enhanced maintenance-free operational lifetime.