malodor vs olfactory sensation

malodor and olfactory sensation both are nouns.

Word	Noun	Adjective	Verb	Adverb
malodor	Yes	No	No	No
olfactory sensation	Yes	No	No	No

As nouns, olfactory sensation is a hypernym of malodor; that is, olfactory sensation is a word with a broader meaning than malodor:

malodor: a distinctive odor that is offensively unpleasant
olfactory sensation: the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form

Other hypernyms of malodor include odor, odour, olfactory perception, smell.

malodor (noun)	olfactory sensation (noun)
a distinctive odor that is offensively unpleasant	the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form