Hi everyone,
Here are some answers to your questions about smoke fluid taken directly from a story published by MR’s sister publication Classic Toy Trains in its January 2003 issue. It was written by Joseph Lechner, who is a college chemistry professor and model railroader.
First, he writes that the smoke isn’t technically “smoke” because there is no combustion. The liquid smoke fluid is vaporized by a heating element inside the locomotive stack. Scientifically, that produces a “fog.”
How?
When the vapors are pushed out of the stack (new locomotives use a minature fan to push the air) and they come in contact with the “cooler” air temperature of a train room (cooler than the heating element) they condense to form what is called a “colloid,” which consists of liquid droplets dispersed in air. That’s a fog.
The colloids tend to stay suspended in the air because each particle has some static electric charge. The particles are small and repel each other, so they do not settle quickly. They look smokey because the particles are large enough to scatter light.
Is it a health hazard?
Lechner writes that manufacturers seldom specify the exact chemical properties of their fluid, but that the toy train smoke fluids are all light oils of varying viscosity.
He also writes that some chemical substances in smoke fluid can be moderate eye irritants and slight irritants to mucous membranes, so common sense suggests that there should be some ventilation in train rooms and that anyone irritated by the smoke should seek fresh air.
The bottom line appears to be that if you like smoke, use it in moderation. If you don’t like it or it causes an allergy-like reaction, stay away from it, but it is not a permanent health hazard.
Neil Besougloff
editor, MR