when used with inductive loads such as electric fans, care must be taken to assure that the TRIAC will turn off correctly at the end of each half-cycle of the AC power.
A snubber circuit (usually of the RC type) is often used between A1 and A2 to assist this turn-off. Snubber circuits are also used to prevent premature triggering, caused for example by voltage spikes in the mains supply. Also, a gate resistor or capacitor (or both in parallel) may be connected between gate and A1 to further prevent false triggering. That, however, increases the required trigger current and / or adds latency (capacitor charging).