PurpleAir PA-II-SD Air Quality Monitor

I've written elsewhere about how to pick the best air quality monitor. PurpleAir impressed me with its precision which was almost reference-grade quality, comparable to sensors that cost thousands of dollars.

As a result, I purchased the PurpleAir PA-II-SD to track the quality of air inside my house. For most people I would recommend the PA-II version which is slightly less expensive but has no built-in memory, and therefore requires continuous wifi access.

The data from this device has already caused me to change some habits to improve my air quality.

Why track air pollution?

The air you breathe may not seem like a major health concern, but it turns out that air pollution is one of the world’s leading killers, responsible for 6.4 million deaths per year.[1]

Air pollution is a major contributor to cardiovascular disease. Children, the elderly, and low-income communities are especially at risk. Evidence suggests that air pollution is linked to a higher risk of diabetes, autism, and lower IQ scores.[1]

Device specifications

Air is made up of small airborne particles like dust, soot, and drops of liquids called particulate matter (PM) which are typically measured in microns, one-millionth of a meter.[1] The PurpleAir monitor measures down to 0.3 micron particles, one of the lowest levels for a consumer device on the market.

The PurpleAir also measures temperature, pressure, and humidity. However, I have found that the temperature isn't very accurate and may be affected by the heat of the internal components.

Some limitations of this device are that it has no display screen so there is nothing to glance at if you want a quick view of your air quality. All measurements must be viewed through the PurpleAir website or downloaded via a script. The device also requires continuous wifi access, except in the case of the SD version which has a built-in memory card that includes all the data.

Unboxing and setup

Healthy air habits

I mounted this device in my bedroom to monitor indoor air pollution and it has already caused me to change some habits. For example, I have noticed that particulate matter is quickly distributed through a house by central air conditioning.

In other words, if you light a candle far away from your bedroom but the air conditioning is on, the soot from that candle will be distributed to your bedroom and every other room in your house. The same is true for cooking indoors or opening a window, both of which introduce particulate matter into your air.

On my PurpleAir, I could quickly see a spike in particulate matter when any of these events occurred. I have come to the conclusion that the best habit is to leave my bedroom door closed with the HEPA filter on and the air conditioning off. When I must turn the air on I make sure that any pollutants have cleared.

Final thoughts

Based on my research the PurpleAir is the most precise consumer air quality monitor on the market. It has some limitations that make it less user-friendly, such as having no display screen, but accuracy is more important to me in this case.

I continue to use this device after several months and enjoy having a way to quantify my indoor air quality.