MultiRAE User’s Guide67If gas or radiation alarm conditions exist (High, Low, Max, Over, STEL, or TWA alarms), the operationpattern switches to a much shorter, one-second-long cycle in which gas measurements are taken for 0.7seconds followed by gamma radiation measurements that are taken during the remaining 0.3 seconds.Like under non-alarm conditions, the pump stays on when gas measurements are taken, but it is turned offwhen gamma radiation is measured.MultiRAE Pro Operation in Multi-Threat Mode in Alarm ConditionsOnce alarm conditions subside, the operation pattern returns to the “55 sec. gas / 5 sec. radiation” cycle.Note: Because of the MultiRAE Pro’s intermittent pump operation in multi-threat mode, during the partof the cycle in which the pump is turned off, the PID sensor lamp is automatically cleaned by ozone thatforms above the PID lamp crystal (this ozone is removed by the air flow when the pump is running.) Thisauto-clean feature reduces PID sensor maintenance frequency.11.2 Gamma Radiation-Only Measurement ModeWhen the instrument is in gamma-only mode, gas sensors are not shown on the display and gasmeasurements are not taken. The pump remains off and gamma radiation is measured all the time in allcases, as illustrated below:MultiRAE Pro Operation in Gamma-Only ModeWARNINGToxic and combustible gases cannot be detected by the MultiRAE when it is operated in gamma-only mode.Activating Gamma-Only Measurement ModeTo activate gamma-only measurement mode:1. Press [N/-] when the instrument is running in normal (multi-threat) mode:
