"Some ventilation is still a good idea though." I think a CO2 meter is an excellent idea, imho it is a good proxy for "air freshness", so also small particles

"Some ventilation is still a good idea though." I think a CO2 meter is an excellent idea, imho it is a good proxy for "air freshness", so also small particles etc. This year I want to try to ventilated more based on CO2 (so close the vents until CO2 becomes unacceptable) and monitor gas use (hooray for Home Assistant).