If you have accidentally let your airlock dry out, (or forgotten to add water to it) it isn't an airlock anymore. Whether it is a traditional style like this:
or a hermetic water seal airlock like this KrautSource kit
...it is no longer functioning as an airlock if the liquid in it dries up. Once an airlock dries out, it is considered an open air ferment. This subjects your ferment to all the molds, yeasts and other funk present in the air.
The first rule of thumb is to keep an eye on your ferments. Check them daily to make sure the water level in your airlock is sufficient. In warmer temperatures you many need to check your ferments multiple times a day. A warm day or warm place can speed up the ferment, and a vigorous ferment can overflow.
If there is mold present, discard the entire ferment. Even if there is no mold present, there may be other issues. Inspect further for Kahm yeast growth or strange and unpleasant odors.
If the ferment seems like it is still viable after exposure to air, you may decide to repack and continue with the fermentation process.
Just remember; when in doubt, throw it out!
It’s part of our mission here at Mountain Feed to help you make delicious, sustainable, homemade food more often. Stop by and say hello on Facebook, Twitter, Instagram or Pinterest. Or, as always, you can do it the old fashioned way and come by the store to speak with one of our in-house experts.