Last Night i ended up going food shopping at my local Safeway, i hadn't eaten dinner and being midnight i ended up just getting some manager discounted hot burritos, 2 for a dollar, practically a steal.
So i wake up this morning, and i'm in a bit of a rush, i turn on the shower, and while im waiting for the water to warm up, i start taking off all of my clothes. First my shorts, then my shirt, and then my left sock, and then my underwear. As i hop into the shower, i'm doing my usual thing. It must of been the bean burritos with hot sauce or something but i let a huge one rip. Now if I was sitting in my chair where i usually fart, I wouldn't even notice. However, while i was scratching myself to look like tony the tiger, i took in a deep whiff of the putrid fumes.
As i started gagging, i couldn't get in any air and almost fainted in the shower. After my near death experience, I ended up googling why shower farts smell soo bad.
I'm too lazy to reword it so here is a copy and paste of an official wiki answer
oddly, but true enough, this is actually a good question? H2O, in the form of water vapor, easily attaches to methane molecules by the chlorine atom, or the sulfur released from bacteria, making the foul smell more readily attach to the nostril lining, subsequently sustaining the odor longer than in a dry climate. In addition, warm vapors will cause any crusted mucus to soften and disengage, providing more surface area within the sinuses. And lastly, (if you are male) the qualitive factor of "worse" is a perception of foreign gases - as to our own emissions, the qualitive factor is "better."
The moral of the story, is that after you fart in the shower, remember to take a break from scratching, and hold your breath for approximately 5 seconds in order to let the shower fart dissapate.
Water vapour makes all smells stronger. It's the reason for "the smell of rain". The soil is distrubed by the rain, and all the water in the air carries the smell to you.