By enabling this feature, the sensor wakes up and takes a measurement at a defined interval (sampling period). If the measured value exceeds the thresholds you have configured, an alarm message is triggered.
Below is the list of transmitters that support this feature:
TX T&H MINI 600-050
TX T&H AMB 600-051
TX T&H E-INK AMB 600-052
TX CO₂ T&H AMB 600-053
TX LIGHT PIR T&H 600-062
If you want to enable alarm thresholds via a downlink, as shown in the link below, this operation requires prior activation of the Report By Exception (RBE) feature:
[LoRaWAN] LoRaWAN Data frames decoding and downlink generator