What causes drain gnats?

Related questions

1. What can I spray on my plants to kill gnats?
2. Why do gnats fly around your face?
3. How do you get rid of gnats in sewer?
4. Why do I have gnats in my bathroom?
5. How do you get rid of biting gnats?
6. Can bleach kill gnats?
7. What kills fungus gnats?
8. How do you get rid of gnats infestation outside?
9. Does Drano kill drain flies?
10. What do gnats do to humans?

Tags

1. #broken
2. #floors
3. #these
4. #place
5. #humid
6. #sometimes
7. #drains
8. #hence
9. #sides
10. #under
11. #typically
12. #begin
13. #inspection
14. #flies
15. #debris
16. #common
17. #drain
18. #breed