Airborne-Infection Control in a Low-Resource Clinic Waiting Room, Priced per Dollar: A Model-Derived Ranked Protocol

A 90 m3 clinic waiting room with 0.5 ACH baseline gives a Wells-Riley tuberculosis infection probability of 0.293 per person (1 infector, 13 quanta/h, 2 h exposure). Wind cross-ventilation (74.36 added ACH, $120) buys the most risk reduction per dollar (24.22 percentage points per $100), followed by an exhaust fan (9.44 ACH, $180), stack ventilation (13.02 ACH, $250) and upper-room ultraviolet (10.0 equivalent ACH, $600). Every single measure reaches the 0.05 probability target under base-case conditions; the recommended protocol pairs the openings with the fan, which alone holds probability at 0.0173 with no wind. SIMULATED, NOT MEASURED.