Clean the air insight with plants. We just feel the need to open the windows in the morning, cause the air seems to be used/ not fresh anymore. With plants insight the air gets enriched with oxygen and water, cleaned from pollution - for a better room climate. Plants that work really efficient would be: Sansevieria, peace lily, kentia palm, dieffenbachia, ivy (https://www.pflanzenfreude.de/die-top-5-luftreinigenden-pflanzen) Although opening the window wouldn't be out of the way - it would be less!
A cheap solution with a lot of benefits and positive side effects for everyone!