Exposure to highly offensive odors such as decomposing flesh, vomits, and the like are known to cause mental disorders and other health problems in medical professionals, military and Homeland Security field personnel. Some of the most frequently reported health complaints include depression, tension, anger, fatigue, and confusion. Other symptoms include headache, nausea, diarrhea, dizziness, and nasal congestion. A number of people also present psychological symptoms.
On a case-by-case basis, this isn't really true.
You get used to decomp. Trust me, I know. I've been in some pretty stinky situations, and I've never seen anybody put Vicks Vaporub on their lip ala Silence of the Lambs. (I do know some folks who, when they have to work extensively with decomposition in a confined setting, squirt a little Febreze on the inside of their face masks, but I've tried it and I can say that it isn't worth the bother.) Mass disasters are different. I can see this kind of stuff being useful in mass-disaster situations, especially when you have civilian volunteers who are novices to the work in general, let alone large numbers of decomposing bodies -- but stockpiling it for that seems kind of like wasted effort, unless there's a central disaster agency (like the US's DMORT) doing the stockpiling.
The thing about decomp is that the smell lingers on you -- your clothes, hair, and your nose so you keep smelling it even if other people don't. I met a guy once who'd been part of the group that cleaned up Jonestown. He said that when he came home, his dog wouldn't come near him. His wife made him strip and wash on the patio. Then she burned his clothes.
He was lying in bed that night when he realized he still smelled it. Then he looked over and realized the smell of Jonestown had permeated his wallet. Which was lying on the nightstand.
Put whatever you want under your nostrils. Won't stop the scent of decomp from doing that.