Plastic Ducky's idea is great. 
If you need something to remove them quickly, this worked last year at my home. I totally eradicated the fruit flies inside, though it took about 3 life cycles to get rid of them all. We live next to a woods, and have all kinds of critters that come in, so we had a huge number of them. Plus I think that the people who lived there before us (the previous year) were not very clean. 
1. Take a wide mouth jar (like what spaghetti sauce comes in.)
2. Put about an inch of cider vinegar (safe around food) in the bottom.
3. Put a piece of plastic wrap over the top, secured with a rubber band.
4. Punch a lot of holes in it, large enough for the flies to easily enter. This was important, because it needs bigger holds than you would think.
5. Set in an area where you see a lot of the flies.
The cider vinegar approximates the smell of rotting fruit, so the flies will be attracted to it. They will crawl through the holes and fly around in the jar, but they're pretty stupid and most can't get out.
Eventually they will fall into the vinegar, where they will be pickled and will not decompose. So they will present little or no food safety issue.
You can change the vinegar periodically, for sanitary reasons, but none of this presents a hazard to food.
The life cycle is 40 to 50 days, so even if you catch them all, some will have laid eggs and will hatch. So you will need to keep it around for several months.
This was almost magical in my home. It may not totally get rid of all of yours around a salad bar, but combine it with treating the drains, it will help out a lot.
And it's better than a candle. 
Martha