Macurco TX-12-AM Instructions D'utilisation page 9

5. The Fan Relay can be configured for latching or non-latching (default) when activated (when the gas concentration exceeds fan
relay set point).
6. The Fan Relay will engage if the fan setting Ammonia concentration is exceeded for longer than the Fan Relay Delay time.
Unless it is configured for latching, the fan relay will disengage once both of these conditions have been met:

Ammonia concentration has dropped below fan setting

Fan Relay Run time has been exceeded
Note that the "disable" fan setting will cause the fan relay to not engage. The fan relay will engage in trouble fault condition (if
the Trouble Fan Setting Option is set to "ON") and will disengage once trouble fault condition is cleared.
7. The Current Loop is 4 mA in clean air and 20 mA for 100 ppm Ammonia
9