When replacing the batteries, this will cause the sensors to do a hard reset, which may cause a gap in data for 1 hour.

If the batteries of your monitor die, the sensors will stop sampling data. When you replace the batteries, the last samples recorded by the monitor before it died will be restored. If it has been weeks or months since the monitor died, there will be a gap in data for this period while the sensors were not functional.

Make sure to use alkaline batteries when changing your batteries and to view any past data sampling, you can do so by logging into https://dashboard.airthings.com/.