Sometimes "decontamination showers" refers to going in to a sterile area, or into an agricultural area where the livestock is at risk of outside contaminants.
The summer between college and grad school, I stayed in my small college town and did temp work. When the office work dried up, they asked if I would do manual labor and offered me a 2-week gig at...of all places...a chicken farm. They also said that there was a strict decontamination protocol, asked my height and boot size (so they could provide overalls and boots that had not been exposed to outside contaminants) and that we were required to shower on the way in and the way out. I was still learning to control erections in casual nude situations. I had mastered relatively short bursts from towel hook to stall in the dorm bathrooms, changing in front of roommates, etc., so while guys saw my penis on a regular basis, open showers were still a huge obstacle. I wondered if it would be open showers, a prospect that made me nervous, but also excited. One strategy was that I wore glasses instead of contacts, so the naked men around me would be blurry, hoping that would reduce the chance of erections.
When I arrived the first day, they had me sign forms, etc., on the office/outside area of the facility, then showed me to the changing/shower facility with changing rooms at both ends and a huge open shower in the middle. Since the shift had already started and I was joining late due to the paperwork, I showered alone, but knew that would be the last time.
The work was every bit exhausting and disgusting as I imagined. I was exhausted by the end of the shift, which probably helped. The other guys were all beefy farm types, which didn't. I took off my glasses, walked quickly to the furthest shower head, ran cold water and faced the wall. After about a minute, I couldn't take it any more, so warmed it up a bit. Finally, I realized I was so exhausted and in need of a hot shower, that I turned up the heat and seemed to keep it all under control. The real moment of accomplishment was when I turned around and joined in the conversation. This was an important passage into manhood...engaging in conversation with other men in an open shower, facing out, penis fully exposed.
After 2 days, I started doing it in my contact lenses. I had to go through the process again, but was able to keep my dick under control after a minute or so of cold water, so I could clearly see everyone else's dicks and I could clearly see that they were making eye contact with me and that my penis was fully in their view. It was exhillerating!