PurpleAir makes sensors that a community of citizen scientists use to collect hyper-local, real-time air-quality data and share it on a map that is accessible to everyone. This category will establish a necessary overview for understanding your PurpleAir sensor.
WiFi Range
The WiFi range is typically about 100 feet. This range can vary depending on anything that impedes a direct path between the sensor and WiFi router. Learn more about what may affect WiFi range from the article, “How Far can a WiFi Signal Travel?”, by Actiontec. Prior to mounting your sensor, use a WiFi-enabled device to test your WiFi’s signal strength at the potential installation location. If you’re having trouble obtaining a signal, slightly adjust your router’s antennae or alter your sensor’s position.
A Note on Temperature and Humidity
The temperature and humidity data are for the sensor itself and are not meant to reflect environmental readings. Heat generated by the WiFi module causes an increase in temperature and a decrease in humidity within the housing. We’ve found that a correction of -8°F correlates closely to the ambient temperature, while a 4% correction correlates closely to the ambient humidity. We have adjusted these values on the PurpleAir map to reflect this.
Power Consumption
All PurpleAir sensors run on 5 volts and the current draw is 180mA. This means the power consumption of a sensor is approximately 1 watt. The daily consumption would be 0.0216 kWh.
A PurpleAir sensor’s power supply will work with an AC input of 100-240V. Power supplies for different countries are available in our online store.
LED Brightness Control
The LEDs in your PurpleAir sensors can be turned off or have their brightness changed. To learn how to do this, view the article Change the LED Settings on your Sensors.
Data Usage
PurpleAir devices send roughly 8 Kilobytes of data to our servers every two minutes. Thus, if a device were connected to WiFi for 30 days without interruption, it would send approximately 173 Megabytes of data.
PurpleAir sensors will also send roughly 8 Kilobytes every two minutes to each registered 3rd party data provider.
For example, a PurpleAir sensor registered with Weather Underground as a 3rd party data provider would send roughly 16 Kilobytes every two minutes. This would be approximately 346 Megabytes every 30 days if WiFi is uninterrupted.
Weather Underground is enabled by default on the PurpleAir registration page. This can be disabled or changed to another 3rd party data provider by updating your device’s registration. A second data provider can also be enabled during registration.
What PurpleAir Sensors Measure
This article has moved here: What Do Purpleair Sensors Measure, and How Do They Work?.
How We Measure Air Quality
This article has moved here: What Do Purpleair Sensors Measure, and How Do They Work?.
Life Expectancy
The life expectancy of a PurpleAir sensor is roughly two years, although some run much longer than that. Regarding the laser counters themselves, much like the cartridge in a printer, these have a lifespan and may need to be replaced over time.
Security
To enhance firmware security, there is no way to load firmware onto PurpleAir sensors over a local network; any updates must come from PurpleAir’s own server as a response to a sensor initiated request. Additionally we’ve made it impossible to change any settings on the sensor with the exception of WiFi settings (SSID and password for the WiFi network).
For those concerned about network security, we recommend connecting security-sensitive devices to their own SSID (WiFi network) or fire-walling them from the rest of your local network.