Zen & Touch Sensors - Color Alert Thresholds Specs & Changeability

1). Can anyone provide a link to the specifications for these 2 sensors that shows the THRESHOLDS for which the sensor color changes ? (For example, does the visual color indication change at 13 PM 2.5, or another threshold ?)

2). Can these color changing thresholds be changed by the user ? (For example, if a user wants their sensor to turn red at lower PM2.5 levels, rather than what the default threshold is set for)


Hi @Facts_Really_Matter

1). Sensor colors are based on the US EPA PM2.5 AQI. Here is a link to a community article that shows those AQI colors. It is also important to note that PurpleAir sensors do not use a static color for each AQI level, but rather a slight gradient.

2.) As of right now, there is no way for users to change the colors or AQIs displayed on their PurpleAir devices. This is a good suggestion, and I will pass it along to our development team.

Please let us know if you need anything else.

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OK, good info.
So do these 2 sensors both display all 6 colors, and remain Green at PM=50, and change to Yellow when PM=51 ?

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At its core, that is correct. However, sensor colors work the same way the PurpleAir Map does; everything is on a gradient scale. For example, a sensor that is at 49 might appear way more yellow than green. Greens get lighter as they transition to yellow, and yellows get darker as they transition to orange etc.


Great info, thanks. But it is unfortunate that the user can not make the unit color more ‘sensitive’, and thus useful for indoor use. Please consider this suggestion for future versions.

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Just tagging this on for some additional information: https://aqs.epa.gov/aqsweb/documents/codetables/aqi_breakpoints.html.

This is the US EPA’s breakpoint threshold table for converting PM mass concentrations into US EPA PM2.5 AQI. Thus, you’ll see that 12 µg/m^3 is equal to 50 on the AQI scale, and so on.

Hope that’s helpful!