A simple and inexpensive method for determining the effective ventilation rate in a negatively pressurized room using airborne particles as a tracer.

The ventilation rate within a negatively pressurized room is usually determined by measuring the exhaust air flow rate. This method does not account for air mixing factors and gives limited information on ventilation efficiency within the room. Effective ventilation rates have been determined using tracer gases such as sulfur hexafluoride (SF6).