This is a followup to getting an indoor air quality sensor setup in my house and to review the results from using a MERV 12 and 14 air filter.
If you wish to see my first blog post about this, see here.
First I'll start out with the MERV 14 and then get into the MERV 12.
In the graph (1) below, the green area is where the furnance was recirculating air. The red on/off boxes are where the fan went on and off. The orange and blue lines are inside and outside AQI respectively. While the air is recirculating, the inside AQI value decreases. This is excellent.
One additional thing you might notice is that it appears the rate of change while the air recirculating improves better as the outside AQI gets lower. The fan/filter have to run less.
Graph 1 above
In the graph (2) below, the first green (unmarked) shaded area is where the MERV 14 was installed, then I have marked where the MERV 12 filter was installed. The green shaded areas indicate where the fan was running. Finally, there is a mark where the MERV 12 was removed and replaced with MERV 14. You can see while the MERV 12 was installed, it made no difference on the AQI value detected by the PMS5003 sensor.
Graph 2 above
I can't say I'm surprised with the results based on the MERV ratings, but I was hopeful there would be some measurable change. I'm curious what a MERV 13 would report. Based on the documentation it should show improvement on the AQI score but not as dramatic.
So for now, I'm going to make sure to have a MERV 14 available for use when these fire events occur. Considering the cost, I won't be using it in the winter time - a cheap MERV 12 will suffice for that.