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I'd like to visualise/measure the flow of air in sauna to optimise the ventilation.

Is there a way to colour the air (non-toxic!!!) so I may watch the flow? Or is there any other accessible technology applicable in the home conditions?

EDIT: Finally I asked a DJ on a wedding for a small amount of the fog-machine liquid and I poured it directly to the sauna stove. It produced some smoke and then it (or maybe rather the gas produced by the heat) started burning, but not with long flames. Apparently the heat wires in the stove are too hot. The produced smoke visualised the air flow sufficiently. The only problem was that the smoke dissolved in the air so farther from the stove it wasn't so distinctive, but it was good enough. Thanks to @dknguyen for the tip how to do it without a fog machine.

Honza Zidek
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  • A smoke generator? Or the classic tufts of cotton or paper... – Solar Mike Jun 30 '21 at 12:40
  • @SolarMike What is a "smoke generator"? For smoke house (meat)? It is toxic!!! – Honza Zidek Jun 30 '21 at 12:42
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    Another name for a smoke generator is a fog machine – DKNguyen Jun 30 '21 at 13:32
  • @HonzaZidek so what they use on film sets kills the actors??? Not really. – Solar Mike Jun 30 '21 at 14:05
  • Oh, that one! It's not cheap... is there anything else how to generate non-toxic smoke in home conditions cheaper? When I searched for smoke generator I found things like this https://www.sausagemaker.com/Smoke-Generator-p/19-1610.htm – Honza Zidek Jun 30 '21 at 14:27
  • Are you changing this into a shopping question? – Solar Mike Jun 30 '21 at 14:45
  • Have you tried soap bubbles? They tend to fall down on their own weight, but they could also point air movements, and making them is easy. – Pere Jul 01 '21 at 12:40
  • @SolarMike "Applicable in home condition" was part of my question since the beginning. Buying an extra equipment is rather not part of it. I don't know anything about it, I even did not have a clue what a smoke generator was. So terms like "*classic* this or that" do not bring any value. I need to measure the airflow in my home sauna. Not in a lab. I don't have a lab equipment, I prefer not buying any expensive tools. I hoped that you experts can come with a genuine advance to an DYI enthusiast, not with sarcastic comments. – Honza Zidek Jul 01 '21 at 14:20
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    Find out if your sauna is hot enough to use fog machine solution directly. Then you just need a bottle of the stuff. Needless to say. use *small* amounts and leave the door open during initial testing. It's not meant to be used in an enclosed space. – DKNguyen Jul 01 '21 at 14:33

2 Answers2

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This NASA article discusses some of the common wind tunnel flow visualization methods.

A fog machine generally uses a heated mixture of polypropylene glycol and water. You can test different mixture concentrations in an electric kettle, and use a plastic tube to plumb the fog stream to the locations you are interested in visualizing the flow.

Tufts or pieces of thread generally work well in higher velocity flows, but you can employ similar techniques with other physical items like helium balloons from the floor, air filled balloons from the ceiling, etc.

enter image description here

ericnutsch
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  • That plastic tube is often called a “smoke wand”... – Solar Mike Jun 30 '21 at 15:45
  • The air-filled balloons sound promising, I will try it. The problem might be that they will not discover the vertical flow, as they will go up or down based on the difference of the temperature inside them and around them. However they still can show the horizontal flow. – Honza Zidek Jul 01 '21 at 14:25
  • After unsuccessful experimenting with the incense sticks, I will have to buy the fog machine solution... – Honza Zidek Jul 06 '21 at 10:37
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    Finally I asked a DJ on a wedding for a small amount of the fog-machine liquid and I poured it directly to the sauna stove. It produced some smoke and then it (or maybe rather the gas produced by the heat) started burning :) but not with long flames. Apparently the heat wires in the stove are too hot. The produced smoke visualised the air flow sufficiently. The only problem was that the smoke dissolved in the air so farther from the stove it wasn't so distinctive, but it was good enough. Thanks for the tip! – Honza Zidek Aug 08 '21 at 20:01
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You can buy an incense stick, which burns slowly and produces perfumed smoke. you then position the incense stick at different points in the sauna and make a video of the resulting smoke trails.

niels nielsen
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  • An incense stick is worth of trying, I will do it. Does the video bring anything more than just observing it with eyes? Like showing something which I would not otherwise notice? – Honza Zidek Jul 01 '21 at 14:27
  • the smoke trails will tell you everything you need to know. this is a very sensitive technique which has been in use for more than a hundred years. – niels nielsen Jul 01 '21 at 17:46
  • Just is there something more you may notice by *recording a video* than just what you discover by *plain watching* the smoke with eyes, without recording? – Honza Zidek Jul 01 '21 at 18:48
  • I tried the incense stick, and the amount of smoke generated was not enough to visualise the airflow. The stick is apparently optimised for smell but not for smoke :) I will have to buy the fog machine solution... Another problem is that the smoke is hot so when I burn it near the flow, it naturally goes up, so I cannot observe if the air is really sucked up from under the door by the stove itself. But I reckon the same issue will be with the smoke machine. – Honza Zidek Jul 06 '21 at 10:33
  • Do you know someone who smokes cigarettes? – niels nielsen Jul 06 '21 at 17:30
  • I loathe the cigarette smoke so much that I would never allow them in my sauna. The smell remains in the room long after and it's difficult to get rid of. The fog machine solution sounds more promising. – Honza Zidek Jul 07 '21 at 07:27