# Low Lying Fog Effect without using Dry Ice or Fog Machine



## amwindl

So here is the deal. The director and Set Designer want a low line fog effect for pretty much the whole show (70min). The space is a studio theatre that has pretty much no air flow in the space so when you use fog in the space it hangs around for a long time. This is the reason why we cant just use a fog chiller and a fog machine because when the fog warms up it just hangs around in the air and makes the whole room smokey. We would use a dry ice machine but the audience is sitting within 3' of the stage an the artistic Director is afraid of the dry ice getting within the audience and causing problems. So does anyone know of any other way to create the effect?

-Thanks


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## sk8rsdad

You could try using some defocused slow moving lighting ripple or cloud effect on the stage floor to give a sense of motion without having anything for your actors to walk through. 

In my venue it could be done with our Roboscan 918's with the prism, glass gobo, and a static breakup gobo in the beam, with some variation in the gobo and prism spin directions and speed to make it a little more random. I expect you could get similar results with enough conventional fixtures and some dual gobo rotators.


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## cprted

The director is concerned about exposing the audience to dry ice fog, but its a-ok for actors???

Chilling the fog will give you a similar effect to dry ice, but it isn't quite the same. I would talk to the TD of the space and see what they recommend and what has worked well in the space for previous shows.


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## amwindl

The problem with the dry ice is the space is basically a black box, and the actors are on a 3' high platform and the audience are on the floor so when the dry ice flows past the stage platforms its going to go right in the audience's faces. 

When cooling the fog, wont it just rise and hang in the air once it heats up?

The effect has never been done in the space so really we are looking for ideas.


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## icewolf08

I would be less concerned with audience exposure and more concerned with the amount of fog you are talking about. To put out dry ice or chemical fog continuously for 70 minutes will eat through consumables like crazy. If you were to do this with dry ice you would need a pretty large supply of ice per show and you would need a really good fogger than can keep the water hot enough for 70 minutes. If you go the chemical fog route with a chiller, you will eat through a lot of fluid over the duration of the show.

The space that you are in has to have some air flow or it would not be a space that you could have an audience in. It may not generate strong air currents, but there has to be some kind of air movement. The dry ice should be safe enough to use in terms of air quality (unless you have people laying down in it). You should also consider that the dry ice may make the floor wet and slippery due to condensation. On the other hand, there have been many studies done on the health risks of chemical fog commissioned by Actors Equity Association and overall, they don't recommend extended exposure.

Probably the best bet is to find out what scenes you really need to use the effect in and then go from there.


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## BDS0111

Question... is this show in the round??? You said it was a studio space. Is the audience going to be surrounding the stage on all four sides??


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## amwindl

BDS0111 said:


> Question... is this show in the round??? You said it was a studio space. Is the audience going to be surrounding the stage on all for sides??



Its a three-quarter trust set up.


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## BDS0111

What kind of platforming are you using?? Sounds like what you might want to try is to duct the fog up from underneath the stage and then create some air flow with fans to pull it upstage and off the stage. You'll have to do an experiment to see what would work for you! Is this a drama or a musical? Would noise from a fogger be an issue?


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## Van

Perhaps a nitrogen fog effect migh be in order, but again 70 minutes a night ? You better have a HUGE budget. Make that HUUge.
Google Nitrogen Fog systems you find a variety of manufacturers.


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## amwindl

BDS0111 said:


> What kind of platforming are you using?? Sounds like what you might want to try is to duct the fog up from underneath the stage and then create some air flow with fans to pull it upstage and off the stage. You'll have to do an experiment to see what would work for you! Is this a drama or a musical? Would noise from a fogger be an issue?



The show is _The Queens_ and unfortunately the Upstage wall is the back wall of the set, there really is no Upstage and off. The space has three door ways, it a black box. The noise from a fogger and fans might be distracting. And they have tried using fog in the space before and it just hangs in the space for a very long time. 

Any Ideas that are outside of the box, because foggers dont work in the space and Dry ice has many issues besides the audience such as the amount needed for the run of the show.


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## seanandkate

Your artistic director is correct in his concerns for the use of dry ice. If you haven't got the airflow to get rid of water based fog, you certainly don't want to run the risk of exposing a captive audience to that volume of carbon dioxide. Plus actors would be at the risk of exposure standing in CO2 fog for 70 minutes. I think sk8tsdad is on the right track with a lighting driven solution.


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## BDS0111

Van has a good suggestion too, although it would be costly!

There are many ways to manipulate the air flow, you just have to experiment and see what works for you. Perhaps the fog wasn't working well before because the ideal fluid wasn't being used??

I guess I didn't see the post about the lighting...that is a good thought too! Great thought!! What is the lighting concept for the production like? You'd need something strong to punch through the other stage light maybe... Could be a great solution.


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## gafftaper

I seriously question the artistic choice of fog for 70 minutes straight. Not only is it a very difficult thing to do, I think the audience will get annoyed with it quickly and it will just be a distraction. This is theater right? There is a reason you've never seen this done before. Is this show about acting or about fog? Continuous fog is just going to be a distraction for the audience as it slowly gets more and more out of control. Use some dry ice fog to set the mood for 5 minutes then cut it and let the actors do their job. The purpose of theater tech is to create the world that the play exists in while staying out of the way of the audience's experience. Any time you do some sort of over the top effect like this you better have a REALLY good reason for it, because you run a high risk of annoying the audience. 

Creating a lighting effect which could be dialed back as the setting is established is a great idea. 

If you are stuck on fog you could try a chemical fogger with a chiller and LeMaitre's extra quick dissipating fog juice. Maybe it will dissipate fast enough to not block the audience's view. 

What's your budget? The best option would be to create a 6" platform on top of the stage. Run duct work into it to let the fog out and then create a perimeter of ducting to suck the fog back out as it reaches the edge. This would be complicated, time consuming, and expensive to do right.


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## Les

Just for future reference, the directors were probably requesting a "low _*lying*_ fog effect". Might help in future searches


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## gafftaper

Spelling fixed for future search purposes.


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## ruinexplorer

Well, if you are looking for long running fog, you should consider what is being used for themed environments, ultrasonic water mist foggers like this. However, this is opening a new set of dilemas. I used this type of systems in a museum that I was working in. Since you state that you have little air flow, this should look nice, problem being where to have the water and how to suitably move the fog. Ideally, you would want the mister to be directly under you perfomance area with a perforated deck to allow the mist to rise up. You would need to have your deck be topped with a non-slip surface since you would undoubtedly have condensation on the deck. The biggest concern with doing this is ensuring electical safety. When installing in the exhibits, we had the luxury of installing the proper GFCI protection as well as barriers to keep personnel and visitors from being near the water. So you would also need to use precautionary measures to prevent electrocution (very possible). I recommend that if this method were to be considered that a licensed electrician be available to provide you with the necessary GFCI protection.


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## BillESC

To accomplish what the director wants, here's how to do it.

First, install an 16 to 24 inch plexiglass trim to the stage. This will create the "pool" the chemical fog lives in.

Second, you will need to refridgerate the floor of the stage probably 10 degrees below the ambient temperature of the venue. You'll have to experiment to fine the minimum amount of cooling required to keep the fog from warming.

Third, duct the fog to the stage from a remote location.

Forth, remove warming fog by having a vacumn duct. (Input up stage right, vacumn out stage left.


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## BillESC

BTW, I'd suggest the actors wear heavier than usual socks.


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## JChenault

seanandkate said:


> Your artistic director is correct in his concerns for the use of dry ice. If you haven't got the airflow to get rid of water based fog, you certainly don't want to run the risk of exposing a captive audience to that volume of carbon dioxide. Plus actors would be at the risk of exposure standing in CO2 fog for 70 minutes. I think sk8tsdad is on the right track with a lighting driven solution.



I've heard this fear of CO2 with dry ice fog, but I have not seen any studies that show it to be a problem. It seems to me that it would take a LOT of dry ice to increase the level of CO2 in the air to toxic levels. Does anyone have any reputable studies that quantify the danger to actors, audience, or crew from extended exposure to a dry ice type of fog?

John


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## gafftaper

Here's a safety notice on City Theatrical's site from the compressed gas association. I'm yet to find a documented death. But there are plenty of warnings like that from fairly reliable and official looking places.


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## Dalamar

gafftaper said:


> Here's a safety notice on City Theatrical's site from the compressed gas association. I'm yet to find a documented death. But there are plenty of warnings like that from fairly reliable and official looking places.


 
Thankfully, there are no casualties reported from using CO2 in a theatrical environment, and, frankly, I would expect nothing less than professional caution every time CO2's involved. 

That said, your problem is, in my opinion, easily solved. 

a) MDG ICE FOG Q, a low lying fog generator, when prepared accordingly, can be operated with Liquid N2 instead of L-CO2. 

b) Once its fog is warmed up, contrary to many other products out there, the fog vanishes completely, instead of rising up and mingling with your atmospheric effect: that's the whole point, isn't it?

c) I laughed at the "heavy socked actors" comment, but that's not entirely a bad idea. 

d) a Full Dewar (Liquid refrigerated CO2 or N2) will provide enough fluid for ~70mins, if the tank is a 230 liters (~3 liters per min). You’ll also use 2.5 liters of MDG Low Fog fluid / hour. Use that to calculate your budget. 

That said, I agree that using that much fog, for that long, is going to distract the audience to almost being annoying and defeat the purpose of the effect. But please, don’t take my word for it. I’m no director…


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## JChenault

gafftaper said:


> Here's a safety notice on City Theatrical's site from the compressed gas association. I'm yet to find a documented death. But there are plenty of warnings like that from fairly reliable and official looking places.



As an exercise ( because I have the mind of an engineer ) I wanted to try and quantify the danger of dry ice fog to humans. ( in this case the audience of the production).

I did some analysis to see just how much area we could make dangerous with ten pounds of dry ice making the absolutely worse assumptions we could. IE if I have a closed room that will keep all of the CO2 in it - how small would that room be to create a danger for any occupants of we injected ten pounds of CO2.

First of all - what volume of gas are we talking about? C02 has a molecular weight of 44 grams/mole. A pound 454 grams - so ten pounds would be 4540 grams or (5450/44) 126 moles ( rounding up). At standard pressure and temperature, a mole occupies 22.4 liters. - so our ten pounds of dry ice would yield about (126 * 22.4) 2823 liters. A liter is 61.024 cubic inches and there are 1728 cubic inches in a cubic foot - so our ten pounds of dry ice would produce about ((2823*61)/1728) 99.6 cubic feet of pure CO2. Let's round up to 100 feet to make the math easier.

The air we breath is 21 percent oxygen. From the Post that Gaff gave us we see that

> 12-15% (of 02) Breathing increases, especially in exertion. Pulse up. Impaired coordination, perception, and judgment.


 So let's set our danger point at 15% O2. IE we may start seeing effects at 15% but they are probably not life threatening. 

If we had a room of a fixed size filled with air - and we could add the CO2 such that it would force out the air, but all of the CO2 would stay in the room, we would have to replace 28.5 percent of the gas with CO2 to get the O2 to 15%. 

So my 100 feet of CO2 would make inhabitable a room that is about 350 cubic feet. 

If my room is 20 x 20 feet ( a smallish orchestra pit ) I would have the bottom 10.5 inches of the space at 15%. If the space were 10 x 20 feet - I would have the bottom 21 inches at 15%.

We can't make any hard analysis with more information ( how much dry ice - how big is the room, etc) but it is clear that I am going through a LOT of dry ice, and the space that it is moving into is really really small with no air flow, and no one lies down in the fog - there is little danger.




All of that said - I'm not sure it makes sense to spend the money, time, effort etc to do that much fog in a show - but I wanted to try and quantify the danger to the audience. 

If anyone sees any holes in the analysis please holler.


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## AdamBair

in a dry ice fog machine, the dry ice is contained fully within the machine, so audience proximity is of no concern. But dry ice is still a no-go you could use liquid nitrogen, but that tends to be on an expensive fog system.

The lighting solution sounds like your best shot. The City Theatrical EFX can give you some nice moving effects, especially if you can pair it with a 70 or 90 degree lens on the source4.


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## Dalamar

AdamBair said:


> in a dry ice fog machine, the dry ice is contained fully within the machine, so audience proximity is of no concern. But dry ice is still a no-go you could use liquid nitrogen, but that tends to be on an expensive fog system.
> 
> The lighting solution sounds like your best shot. The City Theatrical EFX can give you some nice moving effects, especially if you can pair it with a 70 or 90 degree lens on the source4.


 
Yes, L-N2 is pricier than L-CO2: that's the main reason we use it. 

So, my advice to you all, reading this: be mindful when using L-CO2, but use it anyway. It's the best solution to make a sustained, controlable, predictable cue safely.


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## jwl868

JChenault said:


> The air we breath is 21 percent oxygen. From the Post that Gaff gave us we see that So let's set our danger point at 15% O2. IE we may start seeing effects at 15% but they are probably not life threatening.



OSHA defines air as "oxygen deficient" when the oxygen level drops to 19.5% (see 40 CFR 1910.134). I agree with your calculation, but if the 19.5% threshold is used, the volume adversely affected by 10 lb of carbon dioxide increases to 1,500 cubic feet. Still, not much but now the 20' x 20' space is filled to 3.75 feet with an oxygen deficient atmosphere.

Joe


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## icewolf08

AdamBair said:


> in a dry ice fog machine, the dry ice is contained fully within the machine, so audience proximity is of no concern. But dry ice is still a no-go you could use liquid nitrogen, but that tends to be on an expensive fog system.



It is not a question of proximity to dry ice, but to the CO2 gas that is released (producing the fog) into the space as you evaporate the dry ice. The question is if it is safe to release that much CO2.


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## AdamBair

icewolf08 said:


> It is not a question of proximity to dry ice, but to the CO2 gas that is released (producing the fog) into the space as you evaporate the dry ice. The question is if it is safe to release that much CO2.


 Humans exhale about 2 lbs of CO2 a day *, so for every dozen people in the room, that's 1 pound per hour. If your theater HVAC moves enough air for the room to contain 240 people breathing for a hour, then it moves enough air for you to use 20 lbs pf CO2 per hour. Yes there will be people and fog generating at the same time, but this should give you some perspective on just how much dry ice it would take to present a hazard in a room the size of a theater.

* Carbon dioxide - Wikipedia, the free encyclopedia


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## BillESC

Dry ice does not evaporate, rather it sublimates. Goes directly from solid to gas by-passing the usual liquid state.

Although the above engineering is interesting, I don't believe a space, designed to hold public performances, could get a CO without an air exchange system in place.


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## MaddMaxx

Find your local light rental company. There are some great effects instuments available that can give you water, fog, etc..


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## philhaney

amwindl said:


> Any Ideas that are outside of the box...



But by definition, your show is _in _a box.....


AdamBair said:


> in a dry ice fog machine, the dry ice is contained fully within the machine, so audience proximity is of no concern.



Aye, but as has been pointed out, it's the CO2 the dry ice turns into that's the problem. Fog or haze "hangs around for a long time" in this space. CO2 is denser than O2 and will fill the room from the floor up (all that fancy engineering aside - nicely done by the way). It may be safe to use dry ice in this space for 70 minutes, but I wouldn't want to do it.

I would go with the "five minutes to set the mood and then turn it off" method or go with a nice lighting effect.

Even if you go with the "swamp gas" theory and just shoot a small puff up through various random spots on stage every 15 to 30 seconds (a different spot each time), at some point you _will _tick off your audience.....


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## jwl868

I had forgotten, but toxicity effects from carbon dioxide occur at lower concentrations compared to those that would cause oxygen deficient atmospheres:

NIOSH REL: 
5,000 ppm TWA (0.5%)
30,000 ppm STEL (3%)
40,000 ppm IDLH (4%)

Current OSHA PEL: 
5,000 ppm TWA (0.5%)

REL - NIOSH recommended exposure limit.
TWA - indicates a time-weighted average concentration for up to a 10-hour workday during a 40-hour workweek.
STEL - short-term exposure limit; unless noted otherwise, the STEL is a 15-minute TWA exposure that should not be exceeded at any time during a workday. 
IDLH - Immediately Dangerous to Life and Health.
PEL - OSHA permissible exposure limit (This is enforceable).
ppm – parts per million (by volume).


Joe


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## JChenault

jwl868 said:


> I had forgotten, but toxicity effects from carbon dioxide occur at lower concentrations compared to those that would cause oxygen deficient atmospheres:
> 
> NIOSH REL:
> 5,000 ppm TWA (0.5%)
> 30,000 ppm STEL (3%)
> 40,000 ppm IDLH (4%)
> 
> Current OSHA PEL:
> 5,000 ppm TWA (0.5%)



Joel

I was not aware of toxicity issues just due to the CO2 (as opposed to lack of oxygen) - Thanks for the correction. 

So where does this get is on the scale of 'How dangerous could it be in the absolutely worse case we can imagine? ( Note that the scenario is intentionally designed to be the absolute worst case imaginable and is intended to be a mental exercise. )

Let's assume a target max if 1.032% of CO2 in the atmosphere. (CO2 is in the atmosphere at about .032 percent. NIOSH says shortness of breath occurs from 2% to 3%. The exposure limit for 8 hours is 0.5 percent - and for ten minutes is 3 percent. - 1.032% seems reasonable and makes the math easy).

From the earlier analysis we saw that 10 LB of dry ice yields about 100 cubic feet of gas. So we can make uninhabitable about 10,000 cubic feet of space assuming absolutely no ventilation. So our 20 x 20 orchestra pit ( 400 feet square) could be toxic up to 25 in depth. Humm. 

Of course, this also means that the one pound block I put in the Halloween punch would make a 10 x 20 foot room toxic up to a height of 5 feet. Thank goodness for air flow. 

It's also interesting that the safety warning from City Theatrical is ignoring the real issue.


Put putting aside all of that rationalization - you're absolutely right - it is more dangerous than I thought in a perfectly sealed environment. But it has nothing to do with lack of oxygen. Says to me that I need to make sure of air flow when doing dry ice in massive quantities. It's also interesting that the warning sighs are shortness of breath and deep breathing.

Now how much air flow would be needed to make a 20 x 20 room safe I leave as an exercise to the reader. 

Thanks


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