LONDON -- It's not every day you get invited to Paris to spend three hours smelling farts.

Sounds odd, doesn't it? But when you realise it involves some virtual reality technology for a new video game -- and, more importantly, that the game in question is South Park: The Fractured But Whole, the upcoming sequel to The Stick of Truth-- the whole thing starts to make a lot more sense.

Last week, I visited French company Buzzman, who were recently tasked with coming up with a fun accessory to be used in conjunction with the new game.

Ubisoft had an alpha version of the new game ready for me to have a go at. They also had a prototype of the beautifully named Nosulus Rift (the aforementioned VR fart simulator) for me to strap over my face.

To begin with, the main thing I had was questions: How would the Nosulus Rift work? What would its role in the game be? Why had they ploughed so much precious time and money into something so odd?

As the day unfolded though, everything gradually became clearer.

What's the game itself about?

Following on from where The Stick of Truthleft off, The Fractured But Wholesees you -- the new kid in town -- joining Cartman & Co's superhero club to save South Park from an as-yet-unknown evil.

The game is another comedy RPG, which involves a mixture of fighting, puzzle-solving and adventure.

Crucially, it also involves a lot of farting.

As in The Stick of Truth,you can fart while battling enemies, but this time they've really taken the flatulence theme up a notch: farting in The Fractured But Wholeis also used to solve puzzles around town, and even to travel through time.

This is where the Nosulus Rift comes in.

How does the Nosulus Rift work in the game?

The current prototype is a Bane-style mask that you strap over your face. Every time your character farts in the game, the device lights up green and a one-second blast of stench is emitted. When I started playing it was sort of nerve-wracking, because I didn't really know what the different buttons did or when it was going to kick in -- but when it did kick in, I knew about it.

There are two types of smell in the game -- one that's activated only once in the demo when your character sits on the toilet (this is by far the most intense of the two), and another, slightly more bearable smell that's activated more frequently as you fart your way around town.

The video at the top of this article shows me suffering through the worst of the two smells. The following Vine shows the second smell (I'd also gotten a bit more used to it by that point).

What are you actually smelling?

The Nosulus Rift is actually pretty clever. It basically connects to a console via Bluetooth or USB, and is triggered by a high frequency sound that gets tripped whenever you push the "fart" button on your controller. Air gets blasted through the mask, and activates the scent contained within tiny drops found in dual capsules at either end of the device.

“Each time there is a fart in the game we send a trigger and the pumps are activated – so airflow is going through the polymer drops," Valentin Squirelo, the 30-year-old Hardware Engineer at Productman (the sector of Buzzman that focusses on new products), explained to me.

"Basically it’s fart perfume.”

Fart perfume is an unexpectedly accurate way of describing it.

The scent I was smelling whenever the Nosulus Rift erupted in my face is a custom-made fragrance (for want of a better word) created by Isabelle Ferrand, a well-known perfume specialist who's worked for a number of famous French brands.

Over a period of weeks, Ferrand and her team apparently tested around 20-30 different "fragrances" before finally nailing the right one.

"At first, the work seemed very simple," Ferrand explained over a Skype call. "We worked with a lot of raw materials... But it's very difficult to have the smell of flatulence."

In the end, they combined smells from raw materials like onions, chorizo, mango, blackcurrent and notes of jasmine -- it sounds like a strange combination, but the resulting smell is... well, effective.

So is the Nosulus Rift any good?

It's worth mentioning that there are no current plans -- sadly -- to make the Nosulus Rift available to the public. It's going to be featured at some upcoming events like Gamescon, but aside from that it's currently little more than a promotional tool.

It's a fun promotional tool, though. And although -- if it is made publicly available -- it'd be hard to imagine solo players using it for hours on end, it iseasy to imagine a group of friends having some fun with one.

Perhaps more interesting is the technology, and what it says about the direction VR is headed in.

Maybe it won't be too long before we start playing games with all five of our senses?