If your ducts, HVAC unit filters, dryer vents, and a chimney are clean, but the air seems to be still stale, the problem is deeper than what can be seen from the first sight. As buildings became more energy-efficient, they also became more airtight, which increases the potential for poor indoor environmental quality.
That is the reason why we recommend you set AQM (Air Quality Monitor). We do not represent a particular air monitor brand, so we are not trying to sell but to show the importance of setting the device (you can either use our service or set it yourself).
Nowadays those are connected to your phone or pad, which makes it easy for everyone to scan and locate the problem.
As soon as the AQM shows the results, the technicians will know for sure what requires fixing.
Most of the time, the main reason to set an ERV system is to lower to the norm the amounts of CO2 and VOC, which in general overcomes it by 5 times.
Now with the ERV working properly, you will benefit with your indoor air pollution lower level and energy bills will also show the decrease.