Real Life Experiment – Indoor vs Outdoor Air Quality

There are countless times that I stretch the importance of monitoring and managing indoor air quality by keeping an eye on the outdoor air quality/conditions.

In this experiment, I want to demonstrate that it is hard to manage indoor air. I want to state that indoor spaces should be subject to 24/7 monitoring and not a periodic inspection.

The graph below demonstrated that indoor AQ gets influenced by outdoor air and on top of that, the polluted air lingers for a longer time indoors unless there is a mitigation plan (aka filtration) in place.

The graph shows PM2.5 data during a period of 48h hours of continuous monitoring with an indoor and outdoor air quality monitor. The house uses natural ventilation to keep CO2 and VOC concentrations low. During poor air quality events, windows and doors were kept closed.

Once the neighbor started a domestic fire (for an unknown reason) both indoor and outdoor environments were equally influenced. Unfortunately, as automation wasn’t active, it was too late to stop outdoor air from coming indoors. Outdoor air improved faster due to winds and faster dilution of the pollutants, but the indoor air was above WHO AQGs recommended levels (5 μg/m3) for the rest of the day.

Then another fire event of a bigger magnitude occurred, and once more it influenced indoor air in a great extent. The overall 48h average PM2.5 values for the outdoor and indoor air were 8.6 μg/m3 and 13 μg/m3, respectively.


All in all, my exposure to fine particulates was higher indoors, even though the source was outside the house (about 60 meters away). Air purifiers or a central ventilation system with high-quality HEPA filters are recommended. I have found from past experiments that a positive pressure solution is more effective (in most cases) as it keeps VOCs and CO2 at low levels indoors.

Ban Wood Smoke – Stickers

In my effort to help clean air communities to raise awareness (I am not only words), I decided to design three simple circular stickers which I will distribute to the communities once the poll is closed and you have selected the best sticker.

Choose one between the three of them and apply to get stickers once the poll is closed. You can apply for the winning sticker via the contact page. Thank you!

If someone (company, non-profit, individual, etc) wishes to support my effort to print and ship the stickers feel free to reach me.

Size Matters: Why is important to know the Particle Size Distribution?

In a constant effort to educate the community, I highly recommend you to attend my upcoming webinar “Size Matters: Why is important to know the Particle Size Distribution“. The webinar is scheduled for the16th of November, 2022 at 8am EST.

Although it is a business oriented webinar, I will also try to educate in simple terms the attendees on what is PM2.5 and why it falls short as it doesn’t reveal in detail the make up of air pollution.

Unfortunately, any value of PM2.5 can represent a wide variety of particulate distributions, and although it has helped researchers in the past to identify the relationship between air pollution and health issues, nowadays, it falls short. We know that the smaller the particles deeper they travel inside the human body. Quantifying the different sizes can help us understand better the effects particulate pollution has on human health and mitigate air pollution appropriately.

See you there!