As a pre-schooler through about 2nd grade, I thought it was fascinating. I remember climbing to the top of our concrete block fence, which had an alcove that kept the trash barrels out of the alley right of way but easily accessed by the garbage collectors. This alcove wall was just the right height for my 7.5 year old self to get on top of, stand on it, and thus be able to get onto the roughly 7 foot high back fence, and stand on its 8 inch wide top, or sit on it, and watch the fogging machine.

It was just a trailer with a tank and a heater and some kind of blower. It looked like it had a pipe about 8 inches across that stuck out the back, and made a distinct whirring whooshing noise. I think it had a propane tank on it as well, which fueled a small engine that drove a powerful fan. It probably used the exhaust from the engine as a vapor superheater.

My best guess based on memory of what I saw looking closely at the machine, is it seemed to have these little tubes that went into the exhaust pipe from the engine that powered everything. The tubes first went into some kind of fire box - it had a burner in it, because I could see a blue flame through some cracks / air gaps in the sides of it.

The engine would pump the pesticide / oil mix through the tubing, which would then get heated really hot - maybe around 600 degrees or so. The exhaust and this high pressure hot spray would be injected into the air that was sucked through the fan, at a temperature not hot enough to actually ignite it, and this would discharge a very dense white cloud as it drove down the alley.

The "fog" would swirl into all the neighborhood back yards. I distinctly remember it had an oily but kind of clean, smell - and I suspect it was mostly diesel mixed with DDT.

It also could have been "sweet" crude oil, rather than more expensive refined fuel, as the oil wells all around us produced a light weight oil that could be cheaply heated to drive off the "drip gas" or lighter hydrocarbons, and those could be fed straight into the engine, while the heavier components just get hot enough to make a very fine mist after being combined with pesticide.

I thought the thing that actually put out the "fog" bore a striking resemblance to a small jet engine, and it had a whoosh like some kind of internal fan blades that were spinning a lot faster than a normal fan but nowhere as fast as an actual jet compressor or turbine.

Closest thing I've seen in the past 25 years or so, is a snow making machine. these have high horsepower electric motors that spin a set of blades that have stationary vanes so the air velocity is maximized, and a ring of high pressure injectors that spray hot water into the cold air on the mountain. The droplets vaporize and raise the humidity of the air, and passage through the fans almost instantly drops temperatures well below the dew point, which is already far below freezing. The vapor freezes directly into snowflakes, which the air stream now carries up to 50 meters or so where they fall as manmade snow on the ski slopes.

They might have dozens of these machines on a major ski resort mountain that run all night while it is bitter cold, building up fresh powder for the next days' skiers.

You had a healthy, childhood curiosity.  Did it get you into much trouble?

Showtalk said:

You had a healthy, childhood curiosity. Did it get you into much trouble?

Sometimes it did.