Here’s the article.
https://www.greenbuildingadvisor.com/blogs/dept/musings/pinpointing-leaks-fog-machine#sthash.ol4MYntP.dpufAnd several questions were posed with no answers:

Pinpointing Leaks With a Fog Machine
Builders can use theatrical fog to find envelope holes
POSTED ON SEP 18 2009 BY MARTIN HOLLADAY, GBA ADVISOR

Tell-tale fog. Once a theatrical fog machine has clouded the interior of a pressurized building, builders can find envelope leaks by looking outdoors for the escaping fog.
In the last few years, energy consultants have developed a quick and easy way to pinpoint air leaks in a building envelope. The technique uses a theatrical fog machine — a small, inexpensive device that creates smoke-like fog for dances, Halloween parties, or theatrical events. Fog machines have heating elements that vaporize “fog juice,” a solution of water and glycol or water and glycerin.
– See more at: https://www.greenbuildingadvisor.com/blogs/dept/musings/pinpointing-leaks-fog-machine#sthash.ol4MYntP.dpuf

Questions
15.
Mar 31, 2011 3:09 PM ET
fogging the the duct system
by Suzanne Teshera

I’ve only found one brand of fog juice, Rosco, that anyone in the fog machine OR energy conservation industries can tell me won’t leave any residue in the ducts which in turn will attract dust. Or perhaps be harmful to the furnace/air handler. I’ve found one brand whose manufacturer says DO NOT use it for this purpose. So my question is, are there other brands (maybe cheaper and maybe easier to find) than Rosco that anyone actually knows won’t be detrimental when introduced to ducts? I asked at The Energy Conservancy and their answer was,’ “good question, no one’s ever asked.” Anyway, I can’t afford a Rosco, I can’t find one to rent, and I need a fogger but I am not willing to use a fog juice that may cause damage.
16.
Mar 31, 2011 3:13 PM ET
Response to Suzanne
by Martin Holladay, GBA Advisor

Suzanne,
Good question. I suggest you post it on our Q&A page, where more people will see it (and perhaps come up with an answer).