Nitric acid concentrations in southern California museums

An air monitoring network was established at southern California museums to measure both indoor and outdoor gas-phase nitric acid concentrations, rates of gaseous and aerosol nitrate deposition onto building surfaces, and building characteristics such as the rate of air exchange with the outdoors. Mean seasonal indoor HNO sub(3) ranged from less than 0.1 to 1.5 mu g/m super(3). This was less than 1-40% of the outdoor concentrations. Having gathered data on the ventilation system design in the various museums, it was possible to predict the indoor/outdoor ratio of HNO sub(3) on an air quality modeling procedure developed previously. The modeling calculations show that HNO sub(3) deposition on interior surfaces is often the principal sink for HNO sub(3), which accounts for the low HNO sub(3) concentrations observed indoors.