Simulating Indoor Air Quality

To see how changing some parameters affects indoor air quality I have created a basic spreadsheet simulation.

The simulation estimates a 2 hour period and deals with:

1. An initial indoor reading
2. An outdoor reading
3. Outdoor air leakage into the house 
4. A purifier running at a set particle efficiency cleaning a set amount of air per minute

DIY Filter Simulations

To see if the simulation is accurate I have compared it to two sets of observed values.

Simulation 1

 

Not the best fit, the purifier wasn't that good. 

Simulation 2: Use CADR Reduction

According to What’s CADR and How is it Different From Airflow? due to the air filter not evenly processing all air and instead often re-processing already cleaned air the actual volume processed per hour is typically 60% of the air flow.

Closer but now the simulation is not working as well as the actual.

Simulation 3: Use Observed In Out Efficiency

Instead of the MERV rating of 67.5% of PM2.5 particles I will use the observed efficiency from some testing I did of 71%.

Looks much the same.

Simulation 4: Increasing CADR to 70%

Perhaps a MERV filter will have a higher CADR relative to its theoretical filtering rate.


A bit closer

Air Leakage

What impact does leakage of on the air quality?

Simulation 1: Effect of Air Leakage at low outdoor of 35 PM2.5

Lets see how going from 1.0 ACH to 0.5 ACH affects things

Barely a difference.

Simulation 2: Effect of Air Leakage at high outdoor of 150 PM2.5

At high outdoor levels the house air leakage is a real problem.

Phillips 2000 Air Purifier

Simulation 1: HEPA Filter

Using the updated simulation lets see how it goes against the HEPA filter

Wow that is surprisingly close!