Looking for gadget to determine fresh outdoor air forced ventilation

Do you guys know a gadget that monitors the home indoor air to help me determine if I need to introduce fresh air into my home via forced ventilation from outside?


Thanks!

:cheers:

source https://hvac-talk.com/vbb/threads/2235594-Looking-for-gadget-to-determine-fresh-outdoor-air-forced-ventilation?goto=newpost