# Way to see air circulation? **URL:** \ **Category:** Factual Questions\ **Created:** [March 4, 2011, 4:43am UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450 "2011-03-04T04:43:22Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Hennessy](https://avatars.discourse-cdn.com/v4/letter/h/a9a28c/32.png) [@Hennessy](https://boards.straightdope.com/u/Hennessy)\ **Post date:** [March 4, 2011, 4:43am UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/1 "2011-03-04T04:43:22Z")
Probably a dumb question because we all know you can’t see wind. Is it possible to see air circulation in a room using anything? ---
**Author:** ![chacoguy](https://avatars.discourse-cdn.com/v4/letter/c/50afbb/32.png) [@chacoguy](https://boards.straightdope.com/u/chacoguy)\ **Post date:** [March 4, 2011, 4:45am UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/2 "2011-03-04T04:45:12Z")
Smoke? ---
**Author:** ![Hennessy](https://avatars.discourse-cdn.com/v4/letter/h/a9a28c/32.png) [@Hennessy](https://boards.straightdope.com/u/Hennessy)\ **Post date:** [March 4, 2011, 4:47am UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/3 "2011-03-04T04:47:35Z")
I thought that but that would take a lot of smoke. It’s hard to produce that much smoke without hazard, it would be awesome to see though. Colored smoke? ---
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [March 4, 2011, 5:13am UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/4 "2011-03-04T05:13:14Z")
There’s fog machines, though those produce an air current of their own. I’m not sure there’s any way to avoid moving air around in the course of introducing a visible vapor. Is this idle wondering, or are you trying to figure out something about your air circulation? ---
**Author:** ![Hennessy](https://avatars.discourse-cdn.com/v4/letter/h/a9a28c/32.png) [@Hennessy](https://boards.straightdope.com/u/Hennessy)\ **Post date:** [March 4, 2011, 5:23am UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/5 "2011-03-04T05:23:59Z")
Idle wondering, its always nice to see new things. I can spend forever staring at smoke swirling around in that one ray of sun that made it into a dark room. I wondered about a fog machine but when I think about when its foggy outside, I never notice fog moving… ---
**Author:** ![TravisFromOR](https://avatars.discourse-cdn.com/v4/letter/t/cc9497/32.png) [@TravisFromOR](https://boards.straightdope.com/u/TravisFromOR)\ **Post date:** [March 4, 2011, 5:32am UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/6 "2011-03-04T05:32:00Z")
> [@Hennessy](#): > > Idle wondering, its always nice to see new things. I can spend forever staring at smoke swirling around in that one ray of sun that made it into a dark room. > > I wondered about a fog machine but when I think about when its foggy outside, I never notice fog moving… That’s because there’s usually very little wind when it’s foggy. ---
**Author:** ![chacoguy](https://avatars.discourse-cdn.com/v4/letter/c/50afbb/32.png) [@chacoguy](https://boards.straightdope.com/u/chacoguy)\ **Post date:** [March 4, 2011, 5:42am UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/7 "2011-03-04T05:42:02Z")
Just light a stick of incense and move it to wherever you want to observe. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [March 4, 2011, 6:36am UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/8 "2011-03-04T06:36:14Z")
> [@TravisFromOR](#): > > That’s because there’s usually very little wind when it’s foggy. That’s right, fog only forms in very light winds, enough to mix the air slightly but not so much that it all gets blown away. Here’s some coloured smoke being used to show air movement through a wingtip vortex. > **[Redirect Notice](http://www.google.com.au/imgres?imgurl=http:%2F%2Fwww.desktop.aero%2Fappliedaero%2Fpotential3d%2Fimages%2Fimage372.jpg&imgrefurl=http:%2F%2Fwww.desktop.aero%2Fappliedaero%2Fpotential3d%2Fwingmodels.html&usg=__cGBq1fZZzbUotKAepdLpf9Iuzvc=&h=302&w=500&sz=20&hl=en&start=19&sig2=QbSIyyTxPgMg3tQPukwpgw&zoom=1&tbnid=Wv0cwj9ZbOMUhM:&tbnh=129&tbnw=184&ei=94hwTbzbNIqAvgOi6v29AQ&prev=%2Fimages%3Fq%3Dwing%2Bvortex%2Bsmoke%26um%3D1%26hl%3Den%26sa%3DN%26biw%3D1023%26bih%3D703%26tbs%3Disch:10,565&um=1&itbs=1&iact=hc&vpx=496&vpy=140&dur=364&hovh=174&hovw=289&tx=166&ty=97&oei=74hwTfSmHpGKvgOYrcS_AQ&page=2&ndsp=21&ved=1t:429,r:2,s:19&biw=1023&bih=703)** ---
**Author:** ![raindog](https://avatars.discourse-cdn.com/v4/letter/r/2bfe46/32.png) [@raindog](https://boards.straightdope.com/u/raindog)\ **Post date:** [March 4, 2011, 12:53pm UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/9 "2011-03-04T12:53:46Z")
Do you really need to _see_ it, or are you concerned/curious that you’re getting enough/any? Because it certainly can be [_measured._](http://www.alnor-usa.com/?gclid=CK2d5u35tKcCFRN-5Qod21JO_A) ---
**Author:** ![psychonaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/psychonaut/32/4655_2.png) [@psychonaut](https://boards.straightdope.com/u/psychonaut)\ **Post date:** [March 4, 2011, 1:24pm UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/10 "2011-03-04T13:24:14Z")
> [@Hennessy](#): > > Probably a dumb question because we all know you can’t see wind. > > Is it possible to see air circulation in a room using anything? You could use a set of flags or windsocks, though the air flow would have to be pretty strong for this to work. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [March 4, 2011, 2:00pm UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/11 "2011-03-04T14:00:58Z")
> [@psychonaut](#): > > You could use a set of flags or windsocks, though the air flow would have to be pretty strong for this to work. A short string of spider silk stuck on the end of a thin piano wire, attached to floor, ceiling, walls. Chances are, close to the walls the flow won’t be directly at the wall, although it could get wrapped around the wire if the air was swirling. ---
**Author:** ![cantara](https://avatars.discourse-cdn.com/v4/letter/c/6f9a4e/32.png) [@cantara](https://boards.straightdope.com/u/cantara)\ **Post date:** [March 4, 2011, 2:43pm UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/12 "2011-03-04T14:43:06Z")
HVAC professionals may use [various smoke products](http://www.regin.com/prod1.html). I suppose you could try to fill a bunch of balloons with just the right amount of helium to make them the same effective density as the surrounding air, or add some weights to the balloons to make them hover instead of rise. They would be less active than smoke though. ---
**Author:** ![Rocketeer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rocketeer/32/4437_2.png) [@Rocketeer](https://boards.straightdope.com/u/Rocketeer)\ **Post date:** [March 4, 2011, 6:27pm UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/13 "2011-03-04T18:27:53Z")
Helium balloons, weighted with paper clips until they have neutral buoyancy. Oops, too late. ☹ ---
**Author:** ![The\_Second\_Stone](https://avatars.discourse-cdn.com/v4/letter/t/bbe5ce/32.png) [@The\_Second\_Stone](https://boards.straightdope.com/u/The_Second_Stone)\ **Post date:** [March 4, 2011, 6:48pm UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/14 "2011-03-04T18:48:30Z")
I’ve dealt with this for the interiors of automobiles, and smoke sticks are used. They look like incense sticks and put off more smoke than incense, but less than a cigarette. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [March 4, 2011, 6:51pm UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/15 "2011-03-04T18:51:17Z")
Probably more complicated and specific than you want, but _Schlieren Photography_ > **[Schlieren photography](https://en.wikipedia.org/wiki/Schlieren_photography)** > > Schlieren photography is a process for photographing fluid flow. Invented by the German physicist August Toepler in 1864 to study supersonic motion, it is widely used in aeronautical engineering to photograph the flow of air around objects. > The classical implementation of an optical schlieren system uses light from a single collimated source shining on, or from behind, a target object. Variations in refractive index caused by density gradients in the fluid distort the collimated light beam. This... Here are some movies using it (and other techniques) [![](https://img.youtube.com/vi/lSFwH0BVd3Q/hqdefault.jpg "Schlieren photography of moving air") ](https://www.youtube.com/watch?v=lSFwH0BVd3Q) ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [March 4, 2011, 8:02pm UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/16 "2011-03-04T20:02:42Z")
A long piece of tape from a C-120 \* cassette tape on the end of a fishing pole works well. \*The longer play time cassettes have thinner tape. Thicker tape will work too, just doesn’t float as well. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [March 5, 2011, 11:38pm UTC](https://boards.straightdope.com/t/way-to-see-air-circulation/573450/17 "2011-03-05T23:38:57Z")
Google “flow visualization”. Find an easy to visualize situation in which the geometry looks the same and the Reynolds number is the same, and look at that flow - the two will be pretty much the same. “An Album of Fluid motion” by Milton van Dyke (sp?) is a good source. Various smokes, titanium tetrachloride sticks, helium filled bubbles.