Does humid air affect a fluorescent tube starting?

  • What are the specific concerns here and situation you are looking at? Commented Apr 27 at 13:57
  • If the electrical contacts are rusty and corroded or weak...it's a possibility. Commented Apr 27 at 13:59
  • Only if your ballast is ancient. Does it hum when it's running? Time for a modern ballast. Or, a court order requires me to say, consider direct-wire LED and bypass the ballast. Commented Apr 30 at 21:29

2 Answers 2


It should not affect it. Fluorescent lights are closed systems, so humidity should not affect the light. Temperature (cold) can certainly mess with the light starting until it warms up unless you have a fancy light which implements a halogen light as well or some other temperature mitigation strategy.

  • 1
    There are high tension fluorescent lights for cold temps. They usually use a lot of power.
    – crip659
    Commented Apr 27 at 14:17

Yes, but it’s pretty rare. It can happen in two ways: if the humidity is so high that moisture condenses on the lamp and socket, the leakage current can reduce the high voltage pulse needed to initialize ionization below the threshold. As soon as the heat generated by the leakage is enough to dry a spot, that breaks the path and the voltage rises to ionization. You might try cleaning the tubes and fixtures to minimize dirt that facilitates leakage current.

The second way - and I think this is more theoretical than practically significant - is due to the higher specific heat of moisture-laden air. Cold fluorescent lamps take longer to light than warm, and the speed with which they warm up is a function of temperature and the dissipation rate of the heat they generate. Humid air soaks up the heat, causing them to take longer to warm up.
Again, neither of these is common under normal room conditions.

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