To determine the composition of particulate matter (PM) inthe Baroque Librar y Hall, size-resolved sampling has beenperformed during three intensive campaigns in spring, summerand winter 2009. Particles were collected and segregatedinto 10 size fractions (0.025 - 10 μm) using twoBerner type Low Pressure Impactors that sampled theindoor and outdoor environment in parallel. The collectedsamples were analysed gravimetrically, by IonChromatography (IC) and Particle Induced X-Ray Emission(PIXE) giving mass, ionic, and elemental size distributions.Simultaneously, total suspended particles (TSP) were collectedon quartz filters, that were later analysed for elemental(EC) and organic carbon (OC). In addition, indoorand outdoor gaseous ammonia and nitric acid were measuredusing passive diffusion samplers. Typical mass sizedistributions were bimodal with the minimum at about1 μm, with lower concentrations indoors and submicronrange shifted to smaller par ticles. The results of ICrevealed that ammonium sulphate and nitrate form about30% of outdoor and about 20% of indoor mass of submicronfractions of PM, with indoor nitrate concentrationsdecreasing to zero. Most of the ammonium nitrate evaporatedafter penetration indoors probably due to higherindoor temperatures and fast surface deposition of gaseousnitric acid. This process also increased indoor concentrationsof ammonia and could also explain a shift of indoorsize distributions to smaller particles.