On this article I am going to compare three AQI monitors: AirVisual, uHoo and Awair.
All the monitors were placed together in the guest room in my house, as you can see on the picture above. I chose that room because I wanted to be able to isolate the devices from the rest of the house and from human interaction especially for the first 21 measurements. No one was allowed in that room during those measurements. After those 21 random measurements which were taken during 4 days period of time I opened the door and I created some “air pollution”. The whole experiment lasted 10 days. Below you can see the graphs with all the sensors and monitors.
All three devices measured the same fluctuations in temperature. uHoo uses decimals and this is the reason sometimes the lines weren’t inline. AirVisual was 1ºC degree less than the other two but I guess that doesn’t mean anything. Now, I have a theory. The AirVisual device is divided in two zones and the temperature/humidity sensors are placed away from the electronic components where heat may occur. Awair does almost the same by moving away the Temp/Humidity sensors from the main electronic board but they end up in the same zone. Again, this 1ºC difference between them isn’t important and I don’t believe it worth the concern.
Excellent correlation between the fluctuations from the three monitors but again they had up to 10% difference in value. The uHoo monitor uses decimals as well to display the Relative Humidity in case anyone wants precision.
The Carbon Dioxide correlation was very good, each monitor uses a different brand of sensor. uHoo sometimes measured up to 100ppm more than the rest. The software from each device plays an important role here.
Particulate Matter PM2.5
Welcome to crazy town. I am so sorry but Awair’s sensor is off the game, so I am not going to analyze it. uHoo and AirVisual had some correlation but they use different types of sensors and the differences are notable especially when you compare them with time values. AirVisual uses an air fan to draw air into the sensor, this is an active sensor and uHoo uses a passive sensor without an air fan, which means that AirVisual may take a better sample of the air quality during that time in the room. uHoo’s sensor waits the air pollution to reach it, eventually the bad air will reach it (thanks to physics) and it will take a good measurement. The bottom line and my opinion both sensors are good for indoor monitoring and some small adjustments on the algorithm is needed.
Volatile Organic Compounds VOCs
Both devices uHoo and Awair use different sensors. I think they don’t measure the same gases so I can’t say if one is better than the other. Comparing the measurements from the two monitors we can clearly see the differences. For some reason Awair’s sensor couldn’t get a measurement less than 300ppb but again it may measure a gas that uHoo doesn’t. You know my opinion about VOC sensors.