The complete guide
Getting the most out of a table fly fan
The one reliable problem with eating outside
It is not the weather. It is that the moment food reaches the table, flies find it, and the rest of the meal is spent waving a hand back and forth over the plates.
Everything normally reached for is worse than the problem. A spray puts chemicals beside food. Flypaper over a table is unpleasant to look at and worse to walk into. A citronella candle blows out, and does not do a great deal while it is lit.
Why moving air works
Flies will not fly into moving air, and they cannot settle on something that is being disturbed. A fan on the table does not have to kill anything. It just makes that patch of table a place flies do not want to be, and they go and bother somebody else's garden.
That is a lower bar than killing them, and it is also all anyone actually wants at a barbecue.
The blades are the part that matters
This is what separates a fly fan from a desk fan pointed at the food.
The blades are soft-touch and built to stop dead the moment they contact an object. That is a deliberate design decision for a device meant to sit in the middle of a table with people reaching across it and children nearby. A normal fan in that position is an accident waiting to happen, which is why nobody puts one there.
Power, and why it has both options
It runs on batteries or on the DC adapter included in the box.
The adapter is the better choice for a long evening if there is a socket within reach. The battery option is the one that makes it useful at all, because patio tables, picnic blankets and the far end of a garden do not have sockets, and those are exactly the places the problem occurs.
Placing it
Put it in the middle of the table, and put it there before the food comes out rather than after the flies arrive.
It protects the area around itself rather than the whole garden. For a long buffet table, one at each end works far better than one in the middle, and two is still simpler than covering everything with cloths.
Switch it off and wipe it down afterwards. If it is going away for the winter, take the batteries out first: batteries left in a stored appliance are the usual reason it does not work next summer.
It is not a substitute for a screen
Same answer as for the swatters. A window or door screen stops insects getting into the house at all, which will always beat managing them once they are inside. The fly fan is for the table, indoors or out, and is the right tool for that job specifically.