How can I make a trigger_damage sensitive to grenades only? They already work but I need it to be triggered ONLY by grenades and no other weapon. Any help? Thanks

there is a couple of ways of doing this you can do it in code and when the trigger takes damage check that the "type" received is of type,

"MOD_GRENADE_SPLASH" || type == "MOD_GRENADE" || type == "MOD_EXPLOSIVE"

.
you can get this data by doing

damageTrig waittill( "damage", amount, attacker, direction_vec, point, type ); 

the other option is in radiant under the entity window to check the box for no on all types of damage except for explosion and projectile.