OK, there are many aspects this story.
When I first read the title, I honestly read it as "Fast detector", which is reasonable, because fast detectors are useful. But when I read it again, I did a double take. So of course, I had to open the link to the story and figure out what this is.
Turns out that that wasn't the original intent of this detector. Rather, it is trying to sniff any odor in a moving air and to locate the source. Of course, the media, even in China, took it to its most obvious "application" such as sniffing (pun intended) the source of a fart. Question is, what do you do when you find the culprit? Is it unlawful in China for someone to fart in public? Do you shame this individual for such an act?
Finally, it turns out that the prize given is the "Pineapple" prize because "...the fruit which in China is said to be so ugly that only the brave and curious would explore its delicious interior..."
I guess this is another example of beauty in the eye of the beholder. I had never, even a second, consider the pineapple to be an "ugly" fruit. In fact, if you've been in to Hawaii or the tropics (especially in South East Asia where the fruit is abundant), it is considered to be beautiful enough to be used as decorations!
In any case, I don't think this research work is "useless" to even qualify for an Ig Nobel prize.