Fog machines fail at the worst time: the night you set up, with the yard ready and the fog timer ticking. Most of the time the cause is one of a few simple things, and the fix takes under an hour. This guide covers how to tell a clog from a power or fluid problem, how to clean the machine using the steps in the manufacturers’ own manuals, and how to store it so it works again next year. If you are still learning the basics, start with our guide to using a fog machine.

Why is my fog machine not making fog?

Start with the cheap checks before you take anything apart. The table below pulls from the Froggy’s Fog and Chauvet DJ Hurricane 700 manuals; your model may differ, so treat it as a starting point and read your own manual.

What causes a fog machine to clog?

A fog machine works by pushing fluid through a heater that vaporizes it, and leftover residue from that process can build up in the heater over time. Theatre Effects, a fog machine maker, says low-quality fluid, improper fluid composition, and additives like fragrances and colors are common culprits. Both Chauvet and Froggy’s say to use only their water-based fluid and never to add perfume, alcohol, or any flammable liquid. If you are unsure which fluid suits your machine, our fog juice guide breaks down the types.

How do you clean a fog machine step by step?

This is the routine from the Froggy’s Fog manual for its 400 W and 1000 W machines, which it says to do every 40 hours of use:

1. Unplug the machine and let it cool before handling it.
2. Clean the ventilation slots of dust and lint.
3. Drain the remaining fluid from the tank through the filter mesh.
4. Add distilled water to about one third of the tank and run the machine for 10 minutes.
5. Drain the water, then refill about one third of the tank with quality fog fluid.
6. Run the machine for 10 to 15 minutes until fog appears.
7. Wipe the machine clean with a lint-free cloth.
8. Drain any excess fluid back into the original container.

Chauvet’s routine for the Hurricane 700 swaps the distilled water for its own cleaner: empty the fluid, add Chauvet Fog Cleaner, warm up the unit, run it until nearly empty, then refill with fog fluid. Froggy’s also sells a fog machine cleaner that it says to use whenever output drops, or at least once a quarter under regular use. Here is what to gather:

Prices are Amazon listing prices from our September 26 check and may have changed.

Does the vinegar method work for cleaning a fog machine?

You will see a 50/50 mix of distilled water and clear vinegar recommended online. Theatre Effects describes exactly that mix: fill the tank, run the machine, then refill with fresh fog fluid before use or storage. We did not find vinegar in the Froggy’s Fog or Chauvet manuals we checked, which point to distilled water or their own cleaner, so the safest move is to follow the instructions for your specific machine. Theatre Effects also cautions that cleaning will not revive a machine that has stopped producing fog entirely, while Chauvet’s troubleshooting table lists a blockage as a cause of no output and says to clean with its cleaner. If one flush does not help, stop there rather than forcing it.

How do you prevent clogs and store a fog machine?

• Use the right fluid. Stick to good water-based fluid, such as Swamp Juice or Bog Fog, and skip scented or colored additives.
• Never run it dry. Froggy’s says running with no fluid can permanently damage the pump, and Chauvet says not to operate the machine without fluid.
• Test it monthly or twice a year. Chauvet recommends a monthly test run; Froggy’s recommends running a stored machine for 15 or more minutes every 6 months.
• Follow your maker on storage. Chauvet says to run its cleaner through the system before storage and not refill with fluid, while Theatre Effects says never to store a machine empty. Makers disagree, so follow your manual.
• Keep it cool and dry. Froggy’s says to store it away from freezing temperatures, heat above 120°F, and humid areas.

Is it time to replace your fog machine?

If a thorough cleaning and fresh fluid do not bring back the fog, or the machine keeps tripping breakers, it may be simpler to replace it. Both the Froggy’s Fog 400 watt with wired remote and the Chauvet DJ Hurricane 700 list at $49.99 as of our check. Our best fog machines roundup compares more options, and fog machine types explained helps you decide which style fits your haunt. Whichever machine you use, keep it clear of flammable materials: Chauvet notes that fog machines may set off smoke detectors depending on output, and Froggy’s says never to point the nozzle at people or leave it running unattended.

Ready to refill with the right stuff? Choose your fog juice before the big night.