How to Tell When A Sensor Produced Data

Empty Files Downloaded From the API

Sometimes when downloading data from the API, either directly or via the Data Download Tool, you’ll receive empty files that might look like this in a spreadsheet:

Screenshot 2023-07-27 at 10.29.10 AM

Or like this if you look directly at the raw text:

Screenshot 2023-07-27 at 12.21.21 PM

If the API request was completed successfully, this means that the sensor you requested data for did not record any data within the requested timeframe.

Points Deducted for Requests With no Data

You will only be deducted a small amount of points for an API request that returns empty data. In the following example:

  • One single API request is sent
  • Using the get_sensor endpoint at a cost of 1 point
  • Requesting the fields pm2.5_a and pm2.5_b, which are 1 point each per row
  • No data was returned, resulting in an empty file

Only 1 point would be deducted for using the get_sensor endpoint, as no rows of pm2.5 data points were returned.

Point pricing for the API is subject to change, so the exact pricing for API endpoints and data fields may be different than the above example. See the pricing table on for up to date information

Finding Recorded Data

There is currently no way to simply obtain a start date for the sensor from the API. However, you can use monthly averages to see what months a device has recorded data for. A monthly average data point means that the sensor recorded at least 1 data point during that timeframe.

You can do this on the Map by following these steps:

  1. Click the sensor you’d like to examine on the map
  2. Change the averaging period to monthly
  3. Examine the graph to see when the earliest recorded data point is

The example below shows this. By hovering our mouse over the leftmost point in the graph, we can see that the earliest data this sensor recorded was in August, 2020.

You can also make API calls asking for monthly averages. This may be useful when you need to check large amounts of devices.

The Earliest Recorded Data for PurpleAir

PurpleAir was launched in 2015. Thus, the closer you get to that date, the less likely it is that you will find data for a given sensor.

Learn More

Learn how to loop your API calls to obtain large amounts of historical data.
Learn about the PurpleAir map with our Map Startup Guide.
Learn more about which PurpleAir sensor is best for you .