During the recent economic crisis in Greece, fireplaces and wood stoves have been extensively used for domestic heating even in densely populated cities like Athens. Throughout the last winter periods (especially winter 2012–2013), a persistent phenomenon of smoke haze covering many urban and suburban areas of the city was observed. In the framework of the present study, indoor and outdoor PM10 and PM2.5 measurements were conducted in an apartment in suburban Athens during December 2012–February 2013 for two periods. One period with minimal or no wood burning at fireplaces and another period with intense wood burning taking place in the area. The results highlighted the impact of biomass burning on PM mass concentration in the ambient atmosphere as well as the indoor air. OC/EC and K+/EC ratios for both (indoor and outdoor) particle fractions revealed their origin from biomass burning. The most abundant ions were SO42– and NO3– followed by Ca2+, PO43–, Na+ for indoor and outdoor particles with levels typical for this suburban area. Finally, Fe strongly dominated in both indoor and outdoor air while elemental enrichment factors highlighted the anthropogenic origin of trace elements. Indoor to outdoor concentration ratios, especially during the period of extensive fireplace use, showed that carbonaceous particles and some trace species (Cu, K+, Na+) were released in the indoor air.