Glycol Foggers

There are a lot of technologies out there capable of producing fog, mist, and haze. We think that the glycol fogger is the best, in terms of low equipment cost, economy and ease of operation, and safety.
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Introduction to water-based (glycol) fogger

Most modern fog machines use an electrically-heated chamber to vaporize a mixture of water and glycols. These are may be called "glycol foggers" for use with "water-based fluid".

WARNING: There are many kinds of glycols, most of them poisonous. If you are tempted to make your own fog fluid, please read our section on that topic.

[photo] This picture shows a Fog Hog Vaporizer, slightly better than the typical inexpensive unit. It has a 1,000W Heater and is rated for 4,500 cubic feet per minute fog output.

These units are very easy to use: pour the "fog juice" in the tank; let the fogger heat up; and press the button to get fog.

Glycol foggers are primarily rated by the power of their heaters, the common inexpensive units being rated 700 Watts. This number is important, because the more power that the heater draws, the better the job it can do of keeping the "heat exchanger" chamber hot and ready to vaporize the fluid to make fog.

Foggers are also rated as to the volume of fog that they put out. This number is expressed in cubic feet per minute (CFM), and one might think that it has meaning, a 20,000 CFM unit being able to belch more fog than a 15,000 CFM unit. Unfortunately, different companies measure this parameter differently, so it doesn't allow you to do an apples-to-apples comparison from one vendor to another.

Peeking inside a glycol fogger

Glycol foggers are quite simple inside. Let's go on a brief tour...

[photo] This is an American DJ Fog Hog - one of their earliest foggers.

It has a removable tank, visible in back. The remote, not show, has a single light on it and a button. When the fogger is hot and ready, the light comes on. Press the button and you get fog.

The fog comes out of the nozzle that you think you see on the left. But things are not always as they appear - the actual nozzle is a tiny pinhole in a piece of metal hidden within this relatively large nozzle-looking thing.

[photo] This is the inside. The big silvery thing in the forground is the heat exchanger. It is wrapped in insulating fiberglass wool and foil.

Behind is the pump. When you press the button, if the heat exchanger is hot enough, the control circuitry turns on the pump. The pump squirts small quantities of the fog juice into the heat exchanger, which flash-evaporates into large clouds of fog

[photo] This is the control logic of the fogger - its "brain". This circuit takes input from the thermostat and uses it to light the "ready" light. It waits for the remote to "push the button", and uses that to turn on the pump. The control logic also disables the pump unless the heat exchanger is hot; there's no reason to squirt fog juice into a cold heat exchanger.

The new crop of ultra-cheap foggers saves money by using a less fancy control circuit which routes line-voltage through the remote. I rather prefer the additional safety provided by a low-voltage remote.

So, it just boils the fog juice?

One might be tempted to believe that one of these glycol foggers works simply by evaporation - it just boils the fog juice, as one might do in a skillet. In truth, it's a little more complex than that.

Fog juice always consists of a mixture of more than one component, and they all have different boiling points. Here are a few chemicals that one might find in fog juice:
material boiling point
Distilled Water 100 deg C
Propylene Glycol 188 deg C
Glycerine 290 deg C

In general, heating a mixture causes the component with the lowest boiling point to boil off first, followed by the component with the next highest boiling point, etc. This principle is used in distillation to separate mixed liquids.

If this held true for a fogger fueled with such a fluid, you would first get water, then Propylene Glycol, then Glycerine.

I suspect it's a little more complex, involving azotropes and steam distillation...

An azeotrope is a constant-boiling point mixture. It works as if two or more different molecules hook together, producing something that exhibits a different uniform boiling point. This is the case with ethanol and water. You can distill it all day, and won't be able to get better than 50% alcohol. Perhaps something of this kind is happening with the fog juice.

Steam distillation is a process whereby the easily-boiled water vapor carries with it some of the component that would normally require a much higher temperature. This probably explains how scented fog juice works.

And maybe there are other factors, because when you squirt the fog juice into the hot heat exchanger, the resulting high pressure is almost like an explosion wherein things can happen that aren't quite obvious.

Economics of glycol foggers

Glycol foggers are quite convenient and economical. Consider the following: Fluid for a glycol fogger varies wildly by manufacturer. Let's say $20/gallon. The fogger doesn't use much fluid; you might go through a quart of it running all night. Any time you want some fog, you just press a button. That gallon doesn't need any special storage conditions and has a shelf-life of nearly forever.

Some brave souls have built their own glycol foggers by dripping fog juice on inverted clothes irons. In the early days of Halloween-L, some folks made foggers by wrapping copper tubing around soldering irons. These heroic measures are seldom justified nowadays - glycol foggers are now easy and inexpensive to obtain.

Some good deals

Here are some attractive deals for those seeking glycol foggers on a tight budget. Be aware that small foggers like these are not capable of continuous fogging, and must pause to reheat between bursts.

Nice Radio Shack fogger

Radio Shack sells a small fogger that has gotten good reviews in the Halloween community.

[photo] Cat.#: 42-3058

700 Watt Fogger (2500 cu./ft. per minute), with timer/remote

Regular price $99.99

This is one of the best low-end foggers on the market. I don't have one of these particular foggers, but numerous people on the Halloween e-mail list have bought them, and they all like them. The thing that makes it such a good deal is that it comes with a quart of fog fluid and the remote with timer. The remote/timer allows you to set periodic small bursts of fog to keep an area covered. Sooner or later, you will want a timer; pressing the "fog" button every minute or two gets tiring. For most foggers, the timer as an accessory that costs another $40.

It might help that this fogger is carried in-stock by Radio Shack stores across the country.

This package is usually on sale for ~$90 in September.

WARNING - The instructions packed with the fogger recommend cleaning with vinegar solution after use. Several contributors to Halloween-L report that they have damaged the pumps in their foggers by following these instructions. This is one case where I recommend ignoring the manufacturer's instructions - don't use the vinegar flush as a part of routine maintenance.

Radio Shack also sells:

1,000 Watt Fogger (5,000 cu.ft. fog/min), with remote
Regular price $199.99
Cat.#: 970-1267 

Cheap MCM fogger

In the fall of 1999, MCM Electronics made the news on the Halloween-L mailing list by offering a "$49 fogger". Haunters who were watching the cheapest foggers nudge the $100 price barrier were pleasantly shocked by this, and ordered the unit in droves. They soon sold out, but the deal was repeated in 2000. One reader bought three of them.

In spring of 2001, the price went up to $70, but it might come on sale again.

The fogger that crashed through the price barrier is:
company: MCM Electronics
part number: 555-3210
description: $49.00 Party Fogger 700W 2500 Cubic Ft/min, manual (push-button) remote control, fluid not included
Internally, this fogger appears to be exactly the same as this better-known unit:
company: Antari Lighting Ltd.
model number: F-80

The Antari FC 4 timer remote should work with this fogger. Rumor has it that this remote is available for $29.99 from

This unit is a very basic 700 Watt fogger, with dumb remote. The thing that makes it exciting is the low cost. All of a sudden, haunters who were kludging up foggers out of clothes irons, Mr. Coffee machines, and soldering irons had a cost-compatible alternative, of commercial quality.

There is no guarantee that, at the time you read this, MCM will still be offering this deal. But it does prove that glycol foggers can be made and sold at a very attractive price-performance point. And if you look hard enough, you will find them.

Note - When the $50 fogger went up to $70 in spring of 2001, purchaser Robert Benfield reported that he was shipped a model other than the Antari. He reported getting the MBT Brute II Fogger (MSRP $172). So, you better see what you get before buying accessories for it!

2001 - Year of the cheap fogger

In previous years, a glycol fogger was an esoteric bit of machinery not commonly seen. Long used in movies and theatre, these gadgets never had a reason to enter the home. The closest they came was dance clubs. Haunters depended on the DJ supply chain to furnish foggers. And since not everybody in the country is a DJ, quantities stayed relatively low, and prices high.

The year 2001 saw increased emphasis on higher-budget Halloween props and effects.

Once China, Inc., starts making something in quantity, the price plummets. A lot of lighting and DJ gear is made in China, but now they are consciously tapping the Halloween Market for even greater volume. Expect prices to continue to drop.

Is a $40 fogger good enough to be worth buying? Foggers are extremely variable in price. I have three of them. I paid $500 for the nicest one, about one third the MSRP. It is equipped with DMX control, a timer, and 1500W heater. It is the size of a duffel-bag, and heavy. It pumps out fog like there is no tomorrow. You are not coming near that for $40. The question is, "do you need to?" I think that many of the low-end foggers will be "good enough".

There's a down-side to this, though...

A glycol fogger isn't the same as a plastic skeleton. With simple props, even a novice knows what to expect - "hang skeleton in window". But foggers are more complex. People won't read enough of the instructions, and the instructions probably won't cover all their questions.

I predict a large number of disappointed newbies. Sad, really.

Some notes on glycol foggers

Health effects of glycol foggers

If you spend a lot of time in a setting that uses a glycol fogger, you are breathing chemicals. You are not breathing the water that you get from high-pressure water or ultrasonic misters (which is quite harmless). You are not breathing the mineral oil from the oil-based systems (which is relatively nasty). This stuff is between those two extremes, relatively benign - you could drink it - but it is a foreign substance.

The real problem with glycol fog is that the glycol is hygroscopic - it has an affinity for water, and soaks it up. In the lungs, glycol fog has a slight drying effect. This isn't dangerous, but can be irritating, especially for those with sensitive lungs. Prolonged or dense exposure can cause coughing.

Health effects of glycol foggers have been studied for a long time, and continue to be studied. So far, there have been no findings of permanent damage, but some reports of temporary discomfort.

Here are some reports on the safety of glycol foggers:


Glycol foggers are really simply beasts, with little to go wrong. Your first step in trouble-shooting should be to refer to the instructions from the manufacturer. But if you can't find them, we have some suggestions...

I Plugged It In, But It Won't Fog

Glycol foggers need to warm up before they will do anything. They contain heat-sensing equipment so that they won't even try to operate unless they are up to heat.

After filling the unit with the correct fog juice, plug it in, turn it on, and let it warm up. The remote-control should have (at the least) a button and a light on it. The usual drill is for the light to go on when the unit is hot and ready to operate. Be prepared to wait a good, long time for the machine to get hot. Some machines require as long as 10 or 15 minutes. If it isn't ready by that time, I guess you do have problems.

It puts out less fog than when it was new

The fogger probable needs a good internal cleaning. See detailed instructions elsewhere on this page.

It Fogs, But Then Stops

The fogger will only operate as long as the heat-exchanger is hot enough to vaporize the fog juice. The initial warm-up time is dedicated to this task.

But as soon as you press the button, generating fog, that heat is used up, and the heat exchanger cools down. If you have a low-wattage machine, a good long fog burst will cool the machine enough that it will have to stop and reheat.

Inexpensive glycol foggers are not capable of continuous fogging! That doesn't make them bad machines. You just have to know how to use them.

I Want Continuous Fog From My Machine!

In order to keep the fog coming, you have to ration the heat stored in the fogger's heat-exchanger. You do this by making many small bursts of fog, with resting in between. It is the long uninterrupted blasts that cool down the fogger so much that it must stop to reheat.

Your best friend for this is a timer on the fogger that allows you to program the fogger for little regular bursts.

High-end foggers ususlly come with such a timer. For cheaper foggers, a timer is usually available as an add-on. And it's a really good thing to get!

I Want Maximum Fog From My Machine!

If you want the most total fog from your machine, you might be tempted to tape down the "fog" button on the remote control. This actually works. The machine will heat up, get hot enough, start the pump, make some fog, cool down, and shut off the pump until it gets hot again.

The machine will cycle on and off, blasting out fog and shutting off.

The only real danger to the fogger is running it dry. You must always have enough fluid in the tank. If you tape down the fog button, make regular checks on the fluid level.

It Fogs, But Not As Much Or As Long As It Did Before

It probably needs cleaning. We have a section for that.

Other Helpful Sites

Cleaning glycol foggers

All glycol foggers require periodic internal cleaning. You should have received cleaning and storage instructions with your unit; follow them. If you didn't receive cleaning and storage instructions specific to your fogger, try to get them by contacting the manufacturer.

It is important to follow manufacturer instructions, because some foggers are intended to be stored with fluid in them (to keep the seals moist) and others need to be stored dry. Some are made easy to clean, and others require special tools or cleaning fluids. Sticking to manufacture's instructions may extend the life of your equipment and will preserve the warranty.

WARNING - Some fogger manufacturers recommend flushing out the fogger with a solution of vinegar and water after use. Some people have damaged their machines by following these instructions. This is especially tricky, because haunters who only use their machines in October, don't know that they have been damaged until the warranty runs out next year! We recommend that vinegar flushing not be used as a part of normal maintenance. Use it only when you suspect that the fogger has been clogged by mineral buildup, and then flush out the vinegar with generous amounts of distilled water.

If you lack manufacturer's cleaning instructions, you might want to consider doing what we do. Depending on the amount of buildup, we work our way up through three levels of cleaning: nozzle cleaning; distilled water flush; vinegar flush.

Nozzle Cleaning

Distilled Water Flush

If you have no hope of cleaning your fogger according to manufacturer's directions, you might consider this protocol:

Vinegar Flush

If your fogger seems especially dirty, slow to fog, or fast to reheat, you may have mineral deposits in the heat exchanger. Flushing the fog machine with vinegar dissolves mineral deposits.

This type of cleaning is open to debate. Some people do it regularly; others avoid it completely, saying that it damages the fogger.

In our opinion, it is a valid part of fogger maintenance, but should be only used when you really need it and you must thoroughly rinse the vinegar from the machine after it does its job.

Here is how we do a vinegar flush:

Making your own fog fluid

A lot of people are curious about
making your own for fluid, so we added a page on the subject.

Fog Additives

Glycol foggers don't work well with additives in the fog juice, but a lot of people try. This is a great way to ruin your fogger.

Coloring the fog

A frequently-asked question is "Can I add something to the fog to make it colored, or glow in the dark?"

The short answer is "No".

I suspect that a lot of people have ruined their foggers trying to add stuff to the fog juice.

There is no known material that will color the fog without clogging the machine. Heck, there isn't even anything that will color the fog and clog the machine.

Normally, the fog is white. You can give it the illusion of color by shining colored light on it. This actually works very well, and you can change colors on a moment's notice.

You can color the fog from an ultrasonic mister.

The longer answer is:
Certain kinds of additives can be put in glycol fogger juice. Commercial fog juice is available in numerous scents.

In theory, one could have an additive that has a boiling point near the fog juice; has a good color; keeps the color when evaporated; gives a enough color without too much additive; isn't prohibitively expensive; is nontoxic; does not decompose to toxic byproducts; does not damage the seals in the pump; does not corrode or clog the heat exchanger, etc.

Rosco says that they have spent a lot of time looking for such a material, and haven't found it yet. Given the frequency with which the question comes up, there's probably money in a solution, and if the chemists at Rosco can't find an answer, it is unlikely that you will.


Scented fog

There are materials that can be added to fog fluid to give it a nice smell. They tend to be fruity. The most common fragrances are apple, citrus, strawberry, pina colada, and vanilla.

If you really want this, buy it commercially from a dealer in fog machines, and use only a tiny amount.

You can also buy pre-scented fog juice.

Flavored fog

There's a horror story in the Halloween-L archives about rental foggers that come back completely ruined by users who add sugar to the fog juice in order to get "sweet fog".

Making the fog hug the ground

The first time that you use a glycol fogger, you will notice that the fog billows out of the nozzle, out and up - giving a "pea soup" effect. A frequently-asked question is "Can I make the fog hug the ground, like in movie graveyards and swamps?"

For that you need a fog chiller.

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