room ventilation is an important area of environmental and architectural engineering for the application of fluid mechanics. suppose there is a source s (mass per unit time) of air pollution in a room of volume v. examples include carbon monoxide from cigarette smoke or an unvented kerosene heater, emissions from household cleaning products, and vapors given off by evaporation of volatile organic compounds from an open container. let c represent the mass concentration (mass of contaminant per unit volume of air) and q represent the volumetric flow rate of fresh air entering the room. if the room air is well mixed so that the concentration is uniform throughout the room, but varies with time, the differential equation for mass concentration in the room is:
