Yeah. Here is the manual. https://manualzz.com/doc/7054597/nukalerter-manual

From the manual:

Gamma Sensitivity: 18 counts/sec @ 1mR/hr (10μSv/hr) Accuracy (Cs137): ± 20% background through 600R/hr Saturation: No saturation below 1000R/hr Background: <10 counts/minute (Shielded)

Downvote me all you want this isn't useful unless shit gets real.

Here is an interesting paper on gamma-ray monitoring:

https://www.osti.gov/pages/servlets/purl/1356898

Here is [ostensibly]: some specs on the 7121 dectetor the "Nukalert" shitty USB product is based on: https://www.lndinc.com/products/geiger-mueller-tubes/712-2/