Ground-Hugging Fog: NO Chiller, NO Fog Fluid, NO Dry Ice

Intro: Ground-Hugging Fog: NO Chiller, NO Fog Fluid, NO Dry Ice

Ground-Hugging Fog: NO Chiller, NO Fog Fluid, NO Dry Ice

Halloween just wouldn't be Halloween without some creepy low-lying fog. Here is a new approach to getting that spooky ground-hugging fog. No fog chiller, No dry ice, not even a traditional fog machine... But How? Read on....

These fog units may look like fog chillers but they are not fog chillers. You will notice the absence of a traditional heated fog-fluid fog machine in the photo. There just isn't one!

These low-lying fog generators are based on ultrasonic atomizers (pond foggers). The atomizers create super tiny water droplets, like dry ice does. The atomizers are placed in a plastic box with water and the fog is pushed out with a computer fan.

You could use dry ice in these foggers but when using an atomizer, the only consumables are water and electricity (and some conventional ice to keep the atomizer cool).

The atomizers are pretty expensive. The cost for a 12-disk atomizer on amazon is about $130. However, they used to be over $200, so the price is headed in the right direction.

[ News Flash Sept '23 - Just saw a 10-disk atomizer with floats and power supply for $90; 12-disk with power supply (no float) for $115 - Search Amazon for "Pond Fogger" ]

The cost may even be less if you are willing to wait and take the risk of ordering directly from China, such as through AliExpress.

Note that if a price appears to be too good to be true, it probably is. I found an extremely good deal on AliExpress and the seller never shipped. AliExpress refunded the money, but make sure to purchase wisely. Check the seller's rating and how many transactions they have completed.

I highly recommend using atomizers for fog. You can see my other instructables using them:

Full-Size Haunted Cauldron,

Jack-o'-Lantern With Fog (No Dry Ice),

Mini Fogging Cauldron - No Dry Ice, No Fog Fluid

Water Only Fog Machine (No Dry Ice No Fog Juice)

These atomizers make GREAT FOG, so save your money and get one for next Halloween.

This instructable walks through modifying a plastic storage tote to hold the ultrasonic atomizer and adding a fan and fog output duct to give you lots of low, ground-hugging fog with the only consumables being electricity and water.

Note: Wind is a killer. Any air movement will ruin the effect. Also, ambient humidity (more is better) and temperature (lower is better) will impact the effect. If performance is not what you want, you can help things out by spraying your lawn with water to increase the humidity at ground level and the fog should hang longer.

You might be interested in some of my other Halloween related instructables in this collection.

P.S. If you find the Instructables I post interesting please click the "Follow" button above. Thanks!

STEP 1: Trace the Hardboard Lid and Cut Out

We are going to make a temporary lid for the storage tote to mount the computer fan and output duct on. This is going to be made from plastic coated hardboard available from big box hardware stores.

You can use the plastic lid that came with the tote and drill holes in it or drill the holes in the side of the tote but I wanted to make sure the concept worked well before I permanently modified the lid/tote. Using this temporary lid also lets you use the tote for other uses outside of Halloween.

Trace the tote opening onto the coated hardboard.

Cut following the traced line on the coated hardboard to give you a temporary lid.

STEP 2: Drill Fan and Duct Holes

The lid needs to have openings for the computer fan to blow air into the container and for the output duct to let the fog out.

Drill two 3-inch diameter holes into the hardboard.

STEP 3: Insert Atomizer Through Fan Hole

Since the lid is going to be sealed to the tote the power cable of the atomizer needs a way to exit the tote. I decided to have the cable exit through the fan opening. The fans came with a mounting bracket that spaced them above the lid and provided space for the cable to exit under the fan. Or you can just run the power cable under the fan and tape around it later.

STEP 4: Set Ultrasonic Atomizer on Bricks in the Tote

For maximum fog output the atomizing disks need to be about an inch below the water's surface (may vary depending on the atomizer). You can purchase commercial floats that float on the water surface and keep the atomizer at the right depth. But these floats are a bit pricy so I decided to just set my atomizer on bricks.

I set the atomizer on the bricks so that the volume of water in the tote was larger than just setting the atomizer on the bottom of the tote. Having a larger volume of water provides a larger heat sink for the atomizer. The atomizer can generate a great deal of heat and it needs to be kept from overheating so the larger volume and adding ice helps keep it cool.

As fog is generated the water level will decrease and ultimately the atomizer will cease producing fog. Do not run the atomizer without water over it. You can keep it running by adding water by temporarily removing the output duct and adding water and ice through that opening.

If you want you can construct your own float to keep the atomizer at the proper water depth, but I'll leave that for another instructable.

STEP 5: Seal Lid to Tote With Tape

I used HVAC foil tape to seal the lid to the tote to make it air tight (fog tight).

STEP 6: Mount, Seal and Wire the Computer Fan

The fan also needs to be sealed to the lid so that they're no air leaks. Make sure the fan is blowing INTO the tote. Because the fan came on a mounting bracket (surplus) I did did not pay attention to the direction of air flow and I originally installed it blowing air out of the tote. Ooops!

Make sure to have a good seal around the atomizer power cable too.

Connect the computer fan to the appropriately rated low voltage plug-in power supply. My fan was rated 12Vdc so I used a 12Vdc plug-in power supply. The fan black wire is connected to the negative power supply wire. The fan red wire is connected to the positive power supply wire. If the fan has a yellow wire it is not used.

STEP 7: Make Any Needed Duct Mounting Plates

If you want to blow fog out of some type of decoration (jack-o-lantern, gargoyle, etc.) you need a way to attach the duct. This may be as simple as drilling a 3-inch hole into the decorative item or you may want to build a duct mounting plate to attach to it.

The duct mounting plate is simply a piece of hardboard with a 3-inch hole drilled into it. The plate is simply taped over an existing opening in the decorative item.

The duct is connected to the plate (and tote lid for that matter) by 'screwing' the duct into the 3-inch opening. The spiral support wire in the duct lets the duct 'screw' in. If using another type of duct you will have to get creative and come up with a different mounting method.

I attached a duct mounting plate to the bottom of a super large jack-o-lantern so fog would come out of its face.

STEP 8: Make Electrical Connections, If Needed

CAUTION - HAZARDOUS VOLTAGE!

Only make electrical connections with the power cord unplugged. Power needs to be OFF/Disconnected! The DC power supply connects to mains, high voltage. Make sure that the electrical terminals on the DC power supply will be covered and inaccessible. Keep the power supply and its connections away from where people can gain access. In addition to keeping the power supply away from people I would cover the connections area with duct tape (make sure the duct tape does not touch the terminals. DO NOT use the metal foil tape for this purpose). Keep the power supply away from water.

Depending on the atomizer and the DC power supply you obtain, you may need to make the electrical connections to them.

Your power supply may be different than the one shown. Follow the instructions that come with it. Do not make any connections with the power energized. Make sure power is off.

The power cable from the atomizer (with the disks) will need to be connected to the positive (+, red) and negative (-, black) outputs from the power supply.

The mains power cord will need to be connected to the power supply. Green wire is ground (G), the white (or blue) will be neutral (N), and black (or brown) will be line (hot) (L) conductor.

Repeating - Before energizing and when on operational location make sure that the power supply and electrical connections are not accessible and kept away from other people and water as they represent an electrical shock hazard and can be deadly.

STEP 9: Test Out Foggers

The atomizer gets quite warm operating so I always put ice into the water it is operating in. Add water and ice to the tote through the fog exit duct hole by 'unscrewing' the duct, adding the water and ice, and 'screwing' the duct back into the lid. Water should cover the ultrasonic disks by about an inch or so.

Turn on the atomizer and the computer fan and see if fog comes billowing out. Yay!!!!

STEP 10: Position the Foggers and Lay Out Ducts

Position the fogger tote in an inconspicuous location (making sure the power supply and its hazardous electrical connections are kept away from people and water) and run the duct to the area where you want the fog to cover.

Turn on the machine and ENJOY cool-looking, low-lying, ground-hugging, cemetery-worthy creepy FOG!

Comments

[Atilla De Hunn]

I built a simpler one several years ago. Tip - pour some mineral oil (Freshly Squeezed Baby Oil) on top of the water. Makes the fog stick to the ground better.

[wannabemadsci]

Thanks for the comment. I'll have to experiment with that.
You mention that you made a simpler one. In what way was it more simplistic. I like 'simple'. What was yours like? Thx.

[Dootz]

Great tutorial!! We recently had to replace our fridge but we’re able to get ~yrs worth of life out of the OLD one by fixing a broken blade on the little COOLING FAN (used to keep the coils cool). Seeing the fan used here I immediately thought of the one in our old fridge: They run ~$15-$18 thru appliance repair sites (*U could also find the “parts”section of the manual where it’ll give exact part # & usually a site to order replacements) and have a powerful “blow”! Plus they come pre-wired so might be easy to hook to power source!

[wannabemadsci]

Thanks. Great to give an idea for an alternate source for the fan.
It might require some additional mounting brackets.

[ExplorerDad]

This is a great instructable and looks like fun. Thanks for sharing.

Do you know the effect of ambient temp and humidity on the efficacy of this set up?

[wannabemadsci]

Thanks. I believe that the dryer the air the faster the fog will dissipate. Also warmer air would evaporate the water droplets faster too. The fog shown in this instructable was on last Halloween (2022) and in Utah, a very dry state. I also used to live in Massachusetts and atomized fog worked well there too.

[ExplorerDad]

Thank you. I am in the Florida Keys. In Marathon (and Key West) we get pretty into Halloween. Pretty sure too hot and humid to do that. Poop. Oh well. Thanks again.

[mitsured]

I'm in central FL so I have the same concers about the temp. The high humidity should actually help the fog.
I've run a large fogger with 45 gallon trashcan fog chiller for the past few years with good success. The biggest killer for me is wind.any wind at all and the fog won't stick around.

[wannabemadsci]

Humid is great. The more humid the longer the fog will last since the air already has so much moisture in it.

[ExplorerDad]

D’oh. Thank you for clarifying.

[Where_to_Begin]

Just convinced me to spend $100 on a 12 head floating unit...

[wannabemadsci]

Good Luck! Post how it turns out using the "I Made It?" button above. :-)

[natalija23]

Really cool project, thank you for sharing it! A small suggestion (for folks who don't have a computer fan around) -- a small USB-plug fan could work too (seen them at big-box retail stores, and they're similar size as computer fans).

[wannabemadsci]

Thanks, and thanks for the suggestion. I wonder if a USB fan would put out enough air volume. The fan I was using put out about 40 cubic feet of air a minute (cfm). Amazon does carry most everything it seems, including the actual fan I used, SUNON #KD1208PTB1

[saliston]

Great idea and post. I just bought a fogger from Walmart wish I had seen this week ago. Time to start ordering the parts.

[wannabemadsci]

Good Luck! Post how it turns out using the "I Made It?" button above. :-)

[JohnC430]

very nice display on your front lawn

[wannabemadsci]

Thanks!

[install4you]

Great idea.
To build on your ideas, I have 2 brainstorm-level ideas.
1. To save effort unscrewing the duct work mount the duct in its own square of hardboard, cut the duct hole in the plastic tote hardboard lid a little larger, and attach the duct/hardboard to the lid with a hinge. This assembly would just tip open for adding water & ice. You'd need some kind of closure hardware and a seal to keep the tote airtight. The closure could be a barrel bolt, a screen door hook, double wing flush clips, butterfly twist locks, etc. For a seal between the duct mount and the surface of the tote lid, you could use weather strip, any kind or thin foam packing wrap, etc.
A variation on this would be to leave the duct alone & make a separate, small, hinged door in the same manner, minus the hole. It would mean another hole in the tote lid.
2. If you're really ambitious & like to over-engineer things, consider this. Use a toilet fill valve & float to maintain the water level. If you would know how to do something like this, you don't need any how-to from me. To REALLY go over the top, create a separate container with copper tubing loops between the water source & toilet valve. Fill that container with water & lots of ice & you won't have to open the main tote at all. If you actually create such a system that will operate for an extended time without attention, you might want to add a cut-off timer. A 2-gang handy box with a duplex outlet (for atomizer power & fan power supply) and a mechanical on/off switch would do the trick quite well.

I'm past the age when I'd need this device, but happy building to all.

[wannabemadsci]

Thanks for your great suggestions!
I'm looking to build an upgraded unit and I appreciate the input.
You're never too old to get into Halloween! Let your home become the hit of the neighborhood.