The urban territory inhales and coexists. It stopped being dystopic and turned into a new anthropocenic landscape that covers in human agents and its products. The pollution in the atmosphere is a great threat at a global level and the main cause of premature death. The invisible gas microparticles suspended in the air live with us and enter our bodies as quickly and naturally as we breathe. The work is based on the capture of these particles through biomaterial filters (mycelium) that change their color according to the contaminants captured in a backpack with extractors used around Buenos Aires (city and metropolitan region). With the filters used in the different excursions, we made a contemporary cyanometer (a device created in the XIX century to find out how blue the sky could be), a poetic object to visualize how grey/how contaminated our atmosphere can be.