Frequently asked questions :

The sensor is about 4”x 4”x 4” and weighs ¼ lb with the housing. 

The AirU can hang from a hook under an overhang (like a plant), or mounted on a wall, like a smoke detector.

Ideally, the sensor should be mounted in a protected spot outdoors, like under an eave. Your sensor needs a strong Wi-Fi signal ( a minimum of 2 bars on a mobile device ). The AirU’s protective housing is water resistant but not water proof. The AirU should be roughly breathing level (5 ft high or higher). Avoid placing it near kitchen exhaust or dryer vents or less than 4 ft above the ground. The sensor needs to connect to power.

The AirU consumes approximately 1.5 Watts.  The cost of power varies by location, but it will cost less than 1 cent per month.

The AirU works only with personal 2.4 GHz networks. 

The AirU device needs a strong (more than 1 bar) 2.4 GHz WiFi signal.  It cannot use a captive portal (i.e., network that requires manual acceptance of terms through an HTML page before allowing access, like hotels or airports).  It is not capable of WPA-Enterprise, where a certificate and/or username is needed to connect. The system administrator may need to allow access to the device’s mac address (posted on the outside of the housing and the board itself). 

The AirU communicates with the following endpoints, which must be open:

  • mqtt.2030.ltsapis.goog:8883    – data packets every 2 minutes
  • time.google.com:123
  • ota.tetradsensors.com:443– Over-the-Air firmware updates

What if:

  • My sensor goes offline?
      • Ensure that your sensor has power. If not, provide power.  If it has power unplug it for 10 seconds, and plug it back in.  If it does not come back online contact us at contact@tetradsensors.com.
  • My PM2.5 concentrations are 0 ug/m3 for more than 48 hours?
  • Ensure that your sensor has power.  If not, provide power.  If it has power unplug it for 10 seconds, and plug it back in.  If it continues to read zero, contact us contact@tetradsensors.com.
  • My PM2.5 concentrations remain constant (i.e., 4 ug/m3) for more than 24 hours?
      • Unplug your sensor for 10 seconds, and plug it back in. If the numbers still do not change, contact us contact@tetradsensors.com.
  • My PM2.5 concentrations fluctuate by more than 50% on a minute-by-minute, basis?
      • PM2.5 levels can fluctuate greatly on a minute-by-minute basis.  Although we are interested in minute-by-minute readings.  It is more important to determine if your sensor generally follows air quality trends.
  • My PM2.5 concentrations show an unhealthy level > 150 ug/m3 that lasts for a few minutes?
    • This can be normal, and there may be many causes.  One larger particle may have passed through the sensor and provided an erroneous reading, or a malfunctioning vehicle/an individual smoking a cigarette may be near the sensor.

This is not a problem, but you will need to reset your sensor.  Contact tetrad@tetradsensors, and we will explain how to do this. 

This is actually a really challenging question, and researchers are actually evaluating this.  This depends on what types of questions you are interested in answering and the topography and meteorology of your area.  In our experience (mountain valley), we were able to capture significant differences how sensors correlate with each other for particulate matter concentrations associated with a variety of pollution events (“inversions”, wildfires, and fireworks) at spatial distances of one sensor per 1.5 to 2.5 mi2 and elevation differences ranging from 200 to 400 ft.  

Map overlays are only available in an area where we have sufficient number of sensors.

This is UTC, coordinated universal time.