Smoke Units


There are 2 basic kinds of smoke units. The early types, and less expensive, are basically a coil of wire (usually nichrome) submerged in a reservoir of fluid. The heat from the wire will vaporize the fluid.


New: use of ultrasonic atomizer (ater vapor)



a plack in the UK sells the units, but it should be simple to get the parts ourselves.


"Boiler type"

These are typically a tube that holds the fluid, and the coil in the tube: (drawing courtesy George Schreyer)

See more of these older types on George's site:

These types are normally fed a fixed voltage, and as the smoke comes out from the action of boiling, they don't have much smoke, and if you raise the voltage to boil faster, they will burn out if run dry.

This page is oriented towards higher performance units, so no more discussion of boiler types here.

"Wick type & fan driven"

The "better" smoke units have a fiberglas wick wrapped around a heating element. The wick will draw fluid up from a reservoir, and the fan will pump the smoke out. These units make a lot more smoke. Also the fan can easily modulate the amount of smoke. Most smoke units indicate how many drops of fluid to use. I have tested 3 smoke fluids with a syringe and found that they are 37-39 drops per ml / cc. (Aristo, ProtoSmoke, TAS) I used an Accucraft 5 ml syringe (#14224) , but they are all really the same, the droplet size is a function of the surface tension of the fluid.

I recommend you count out your droplets from your smoke bottle and get your drop/ml down and then just use a syringe.

Smoke Fluid

There's a number of manufacturers that sell smoke fluid. I have had good luck with Aristo fluid (but they are now out of business), but no bad experiences with any of the others. Here's a place that has scented fluid:

There's also MTH Proto -Smoke, Lionel premium. Most of them are fine, and you may want to check wicks after some time for buildup.

Some people try using lamp oil or tiki torch fluid, etc in the quest to save money. Often the result is clogged smoke units. There are some people who have success, and many more that have damaged their smoke units. Normally if it is a light solvent, and if you leave a film of it on a surface, it does not damage paint and does not become sticky, it will be fine. Stick with the name brands.

Brands of smoke units, in alphabetical order

Various notes, some are no longer made, but come up on the market, so they are here. I will make some comments on them, mostly from direct experience. Nowadays people usually want more that a continuous trickle of smoke, and many modern decoders support this, modulating the heater and the fan.

Aristo-Craft smoke units - no longer manufactured

There are many different smoke units from Aristo, from the simple heater type that is used in the cabooses to the latest style, called the "Aristo Prime Mover" smoke unit with electronics and a fan.

CLICK HERE for a specific page on all the Aristo units under Aristo Motive power, including an in-depth explanation on why the electronics in the "prime mover" one fail so often. If you have an Aristo smoke unit, be sure to read that page.

For adding to other locos and purposed of comparison, only consider the "Prime Mover" one, shown below, with the fan built in. This one is the best one, used in the latest locomotives, fan driven and a small microprocessor to control the heater. Part number ART-29311

When these work, they usually put out a reasonable quantity of smoke, and have a reasonable run time. Figure on 20 minutes on a filling.

Do not overfill, even though the reservoir can handle 4.5 milliliter, the design allows fluid to slop or condense onto the circuit board, and it attacks the electrolytic caps, swelling the rubber ends and popping them off the circuit board. This is one common cause of failure. There is no way to keep fluid from condensing on the circuit board, since the circuitry is in the chamber with the fan, and that chamber is connected to the fluid chamber.

I recommend 4 ml of fluid max normally when bone dry.

They are very inconsistent and many will only run for a few minutes before shutting off. Again the link above gives clear reasons of why this happens. But if you bypass the electronics and just control the motor and heater directly ("Direct Smoke"), they are very good performing and the best deal cost wise.

patent pending


Again, there are several different types of smoke units in Aristo locos and cabooses. Read the Aristo smoke unit page listed above.

Harbor Models

I don't have a lot of direct experience, but much has been written and there was a lot of interest since it has huge volumes of smoke. The downside is it draws 2 amps at 12 volts and it's big. The plus side is huge volumes of smoke and a large reservoir.

What I have read can be condensed into no one has modulated the fan speed for "chuffing" and many have had them melt. With such a large amp draw, there are not decoders that can modulate the heater, so the thing runs full blast. In 2012 they announced you could vary the fan speed, have not tested this unit. The amp draw of the fan has not been reported, most decoders can only handle 1/2 amp for the fan.


The dimensions on the web site are not correct, the dimensions from an actual owner are: about 2 inches on each side and 1.5 inches tall, but the fan adds another 1.5 inches, so the entire unit is 2 inches wide, 3.5 inches long and 1.5 inches tall.

this will be a tough fit in most locos. You might consider putting it in the tender and then running a hose to the front of the loco.

I've seen several people use this, and really overdrove it and melted things. This unit puts out a lot of heat, so mount and duct it properly.


For the simple units, LGB uses Seuth "boiler type" smoke units. See Seuth, LGB does not make any smoke units.

LGB usually uses Seuthe smoke units, just simple heating elements, no voltage regulation, and they are not known for high smoke output (they cannot since there is no regulation, power monitoring, etc)

LGB will also use Massoth smoke units in the higher end locos.



Massoth makes several smoke units, as of 2019, there are 3, a DC only model, and 2 DCC motels.

8413101 Pulsed Smoke Generator (DC)

Can use either hall effect sensor or a SUSI bus connection (weird on a DC component). Holds 4 to 6 cc of fluid. Note that this unit can draw up to 4 amps.Has dip switches for diesel/steam, and 4 or 2 chuffs per revolution for steam mode. Around $100



8413501 Pulsed Smoke Generator (DCC)

The same product that will take DCC signals. About same price as the DC model and same specs.


Technical specifications

  • Operating voltage : 5 - 24V DC [8413101]; 18 -24V DCC [8413501]
  • Operating current: 1200mA [8413101]; 600mA [8413501]
  • Operating temperature: -4°F to 122°F
  • Capacity: 4cc (optimum); 10cc (Maximum)
  • Dimensions: 54x42x30mm

8415001 Pulsed Smoker (DCC)

This is a new model that has a curved top and fits better in steam locos

It's only 30 mm wide.

Technical specifications

  • Operating voltage : 18 -24V DCC
  • Operating current: 1000mA
  • Operating temperature: -4°F to 122°F
  • Capacity: 5cc (optimum); 10cc (Maximum)
  • Dimensions: 54x42x30mm

MTH (Mike's Train House) smoke units:

MTH is out of business as a manufacturer of trains, but apparently Mike kept the parts business. During their heyday, it was hard to get parts if you were not replacing a damaged unit in exchange, now even more difficult, but keep an eye out.

These units are very well made, metal bodies, several different sizes.

Many people are trying these in customizing, but they are really large: (the MTH is on top, the TAS below).


The MTH unit above measures about 3" long x 1-3/8" wide x 1-3/4" tall (thanks for the pictures and measurements Chuck!)

I don't know the MTH model above.

The motor and the heating element are directly connected to the 4 wires, no electronics involved, in the stock MTH systems, all the brains are on the mth board.

One negative, there is no local heat sensor to monitor the actual temperature of the heating element.

I have ordered the one from the Hudson  ( Proto-Sound 2.0® ) AA-0000032 50.00 ( 6.0x3.0x4.4mm brass cup )( 7.5mm long posts )

It's just under an inch wide, 1.4" long, and about 1.3" tall overall, not including the brass stack. It was $57 from MTH.

part number for the heating element: (MTH part # AI-0000018)

fan part number (MTH part # BE-0000041


 Often used in older LGB locos.

Seuth makes several different smoke units, just simple heaters with no voltage regulation, etc.

Nominal VoltageWorking voltageWire color

(LGB uses 6.2 to 6.8)

Black and White
18??Brown and Yellow
2416-22White and White


Most modern LGB locos have decoders or are decoder ready, so the 5 volt unit seems to be more common. Some people have had issues driving these smoke units from a DCC decoder, and have switched to a lower voltage model to allow more smoke volume, there is a model 4E Seuth which is rated 3 to 4.5 volts (but often sold as a 5 volt model) This 4E model has Brown and White wires, as opposed to the 3 other units above.  For example Piko sells the 4E as a 5 volt unit part number 36142. Thanks to R. Wolfe for this information.


Train America Studios (TAS) - no longer manufactured

This company made one of the nicest aftermarket units, and they have 2 modes, a diesel mode, where the fan speed increases with speed, and a "puff 'n chuff" mode, where you can pulse the fan to match the chuffs, usually tie to the chuff switch. Unfortunately, in 2009, they were bought by Lionel, and then deep sixed. You will find these units in USAT locos sometimes, like the Big Boy, the Hudson, etc. (not in the normal line of plastic bodied diesels). Too bad.

Here is a top view:


  • The three pin plug next to the the aluminum tank/reservoir is for power, ground and chuff.
    • The leftmost wire, furthest from the tank is the "chuff" input, grounding it makes the fan go full speed.
    • the middle wire is ground
    • the rightmost wire, nearest the reservoir is positive
  • The connector at the far left goes the to fan motor, as you can clearly see.
  • The jumper between these 2 connectors controls "steam chuff" mode vs. "diesel notch" mode. The jumper is in the "Steam chuff" mode in this picture


TAS Tips:

  • Many units are supplied with a full wave bridge wired to the ground and plus leads to avoid destruction due to reversed supply voltage.
  • The "DCC" versions may have different PIC code (that is the program in the microprocessor) and a "larger value" heating element. This note was from Mike Regan at TAStudios.
  • I did not measure the current draw of the "chuff" input, it's low current. Isolate from other leads if you are connecting more than one thing to your locmotive cam/reed switch. (use a diode)
  • Notice the jumper between the power connector and the motor connector. It is in the "steam loco" position, the other position is the diesel position.(Steam closest to the reservoir).
  • They made AC and DC versions. The internal circuitry is different. The AC ones use a Triac to turn the heating element on and off, the DC versions use a transistor. So beware if you come upon a used on, it could be an AC version, which will not operate properly on DC.
  • The unit can draw up to about 1.8 amps before it goes into overload protection.
  • DO NOT connect the chuff input to positive DC, it will destroy the unit (wow, but this info directly from TAS)
  • Paul Burch informs me that a replacement heater (usually 27 ohm) can be gotten from Lionel, part number 6008141055. Link to Lionel parts site:

Shown belos is a TAS installation in an Aristo mallet by R.J. DeBerg:



I received mine recently, and will use the "puff 'n chuff" feature on my AML K4, which has a chuff cam. The model I got is the TAS-2004.

When you order a DC unit, you need to tell them what operating voltage you use. I could not get them to give me a straight answer, but I think they set a regulator or dropping resistor somewhere. The DC unit comes with a full wave bridge rectifier (so the unit can be connected to the rails irrespective of polarity), so you can use them on DCC also.

It is a good looking unit, with the circuitry isolated from the smoke fluid. The fluid reservoir and the smoke chamber are in one metal casting, which is sealed to the circuit board.

They also have a TAS-1022 "Puff N Chuff" synchronized smoke upgrade. It is a control for a fan driven unit to pulse the fan in time with the chuff switch. It also includes a 5 volt power board (I assume that is needed to drive the logic circuitry) in addition to the Puff N Chuff board. I will have to try this out on the MTH fan when I try the MTH unit.


An inexpensive smoke unit, with just 4 connections, 2 to the fan, and 2 to the heater, ideal for use with a decoder that drives them directly.

Originally Train-Li offered a rewired Aristo-Craft unit re-wired to bypass the original regulating mechanism and just connect directly to the fan and heater. The unit they sell now looks identical to the original Aristo unit, you see the 4 wires, 2 to the fan, 2 to the heater. Great way to make smoke with decoders that drive these directly, no fuss, no muss, no having several decoders to make work together like the Massoth nightmare.

In theory you can also run the heater at a constant 5 volts.

USA Trains smoke units:

Again, like Aristo, there have been several variations. The early ones were a small square unit, very thin, no fan, just a heating element and a wick and did not work well.

The picture below (courtesy George Schreyer) shows the 5v regulator board, and 2 smoke units, the one on the right shows the heating element, which is vertical, and the small redervoir. So this is a simple heating element that just vaporizes the fluid, small fluid capacity.

gp9 smoke system

The newer smoke units are metal bodied, have a fan and a separate circuit board that controls the motor and the heater. I have found these to be very reliable. The quantity of smoke is not great, but they work and come stock.

In stock form, i.e. running from the USAT power board, using 40 drops fo fluid, one quit about 9.5 minutes, the other 11.25 minutes, then turned itself back on and ran another few seconds, less than one minute

they both restarted when additional fluid was added (motors started, did not remove power, engine was shut down)

These units lend themselves very well to "direct smoke" setups where the decoder drives the fan and heater directly, like the QSI and Zimo.

Reservoir capacity seems to be about 2cc. The fan runs on 5 volts and the heater element gets around 6-7 volts.

Here is a USAT smoke unit in "direct smoke" mode via a QSI Titan decoder:

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