touch off vs set off

touch off and set off both are verbs.

Word	Noun	Adjective	Verb	Adverb
touch off	No	No	Yes	No
set off	No	No	Yes	No

As verbs, touch off and set off are synonyms defined as:

Other synonyms of touch off include activate, actuate, spark, spark off, trigger, trigger off, trip.

touch off (verb)	set off (verb)
put in motion or move to act	cause to burst with a violent release of energy
	set in motion or cause to begin
	direct attention to, as if by means of contrast
	provoke or stir up
	put in motion or move to act
	depart for someplace
	make up for