The above Ad will no longer appear after you Sign Up for Free!

cryogenics and co2?

Discussion in 'Special Effects' started by JahJahwarrior, Mar 21, 2006.

  1. JahJahwarrior

    JahJahwarrior Active Member

    Messages:
    526
    Likes Received:
    1
    Hey...I was thinking recently that using co2 to produce jets of smoke would be pretty simple, and reasonably safe. As long as you are a few feet from thenozzle, there should be no problems with freezing (I have a little bit of experience with liquid co2, from playing paintball. Once upon a time, I managed to get a valve stuck, venting co2 right onto my wrist. 3rd degree burn, biggest blister I've ever seen, and becuase it was on my wrist, for months afterwards the burnt area would bleed just a bit--everytime I'd flex my wrist, it'd crack the scab a bit. but if you are even a foot away, it shouldn't harm you, I'd think), and bulk tanks of co2 aren't that much to rent. Does anyone know much on them? I cannot find tons on google....has anyone used them? am I wrong about how safe they are? Can I build a system myself/has anyone here done it, or can I buy one cheaply?

    Thanks!
     
  2. Mayhem

    Mayhem Senior Team Emeritus Premium Member

    Messages:
    1,790
    Likes Received:
    4
    Location:
    Australia
    Motley Crue had CO2 ‘smoke’ for their last tour and although I didn’t get a good look at the system, it seemed fairly simple in design. There were several “nozzles” across the front that were about 2” in diameter and 4” long. I’m guessing that the feed pipe was about 1/2.

    During the gig I was side of stage and the CO2 jets were loud but also very effective. However, long duration blasts did result in hail falling down on the stage!

    Unfortunately I never got to see how the system was controlled but I imagine that all the valves and couplers would have to be fairly large to reduce the risk of icing up.

    All in all, a cool look but very noisy and definitely something that you do not want to be too close too.
     
  3. len

    len Well-Known Member

    Messages:
    2,709
    Likes Received:
    204
    Location:
    Chicagoland
    http://www.effectsco.com/index3.htm is one place that makes CO2 jets, etc. They have a couple moving heads which are dmx controllable. The key to the system is the oxygen sensor. Even though CO2 won't do much damage to skin if the jets are far away, they can force all the oxygen out of a room, which is a bad thing. I've never worked with them, but they are cool looking in the video.
     
  4. Mayhem

    Mayhem Senior Team Emeritus Premium Member

    Messages:
    1,790
    Likes Received:
    4
    Location:
    Australia
    Excellent point and one that is of upmost importance. This is one reason that CO2 is very good in fire extinguishers.

    Wonder if those little DMX units could find a function as a remote fire control unit. How cool would you look if you were to put out a stage fire from the comfort of the booth!
     
  5. koncept

    koncept Active Member

    Messages:
    590
    Likes Received:
    3
    Location:
    .
    that would be amazing, but would probaly require large ammounts of co2 depending upon stage size and size of the fire. all in all i think it would be a very cool effect for theatre if you did not need to worry about actors being injured by it.
     
  6. JahJahwarrior

    JahJahwarrior Active Member

    Messages:
    526
    Likes Received:
    1
    Eh, should be easy enough to calculate and have a wide safety margin to keep enough oxygen in the room. Plus, a few doors culd be opened and fans put in place before hand to circulate. I've got a chem teacher who might could help me figure out how to make sure we keep o2 in the room :)
     
  7. Radman

    Radman Well-Known Member

    Messages:
    1,219
    Likes Received:
    7
    Location:
    Franklin, TN
    Hehe or the actors could wear SCBAs (SCUBA minus the underwater) hehe I bet the costumer would love figuring out how to hide that under the costume... :D
     
  8. koncept

    koncept Active Member

    Messages:
    590
    Likes Received:
    3
    Location:
    .
    if you do get to use these, please take pictures and post comments. i would be very interested in thier performance. I think it is safe so long as actors are not directly breathing the streams in.
     
  9. len

    len Well-Known Member

    Messages:
    2,709
    Likes Received:
    204
    Location:
    Chicagoland
    The only place I've seen them used is in nightclubs, but that's probably because I don't go to the theatre as much as I'm in nightclubs. There is also a nitrogen system that chills the air. It's pretty intense.
     
    Last edited by a moderator: Mar 23, 2006
  10. MHSTech

    MHSTech Active Member

    Messages:
    138
    Likes Received:
    0
    Location:
    Ohio
    If you can get DMX to control a servo motor...we're in business.

    Just as long as the working area doesn't reach over 426 PPM of Co2, you're good. I may be wrong, but I believe 426 PPM is the most Co2 you can take without getting poisoned.
     
  11. kingfisher1

    kingfisher1 Active Member

    Messages:
    377
    Likes Received:
    1
    Might want to leave a little margin of error. thtas kinda like saying "hey, this rope hold 90lbs! i weigh ninety pounds! lets dangel over a cliff with it" :)
     
  12. Radman

    Radman Well-Known Member

    Messages:
    1,219
    Likes Received:
    7
    Location:
    Franklin, TN
    What kind of person weighs 90 pounds? (Not to throw a fork in you logic or anything...) :D

    I think it sounds cool. I've experienced a bit of CO2 from paintball and FX stuff as well.
     
  13. Mayhem

    Mayhem Senior Team Emeritus Premium Member

    Messages:
    1,790
    Likes Received:
    4
    Location:
    Australia
    The kid in the “Skinny white boy” banner ad for T-shirt hell!
     
  14. jwl868

    jwl868 Active Member

    Messages:
    697
    Likes Received:
    47
    Location:
    Pittsburgh, PA
    On the subject of how much CO2 becomes hazardous:

    While there is the possibility that the CO2 could displace all of the oxygen in a room or at floor level, the ventilation in most auditoriums etc should prevent this. Low spots where the heavy gas could collect with limited air movement (such as an orchestra pit or a small basement storage room below a stage) could be a greater problem, but even then it’s a matter of additional caution. Industrial situations where deaths from lack of oxygen (or poisonous gas) tend to be in confined, limited access, and limited ventilation locations, such as sub basements, tanks, and sometimes deep excavations.

    Regardless, the consideration is not necessarily the amount of carbon dioxide that will displace all of the air, but rather the quantity of CO2 that will mix with the air and displace just enough oxygen such that the oxygen concentration is reduced from the normal 21 % down to 19.5 %, this being the definition of "oxygen deficient". [Please note that these are volume percentages not weight percentages; by convention gas percentages and concentrations are always on a volume basis unless otherwise noted.] It is at this percentage where one begins to suffer from lack of oxygen. Zero % oxygen is fatal – but so is 15% oxygen. (The best analogy someone gave me was that in the lungs, oxygen transfers across membranes from the air to the blood because, and at 21 %, the oxygen partial pressure is greater then the oxygen pressure in the blood. But when the oxygen percentage in the air drops below 19.5%, the oxygen pressure is lower than that in the blood and the transfer does not take place.)

    So if you do this calculation, the amount of CO2 is not the volume of the room, but rather, a small percentage of it. Also, it is not a 1 to 1 displacement of oxygen by the CO2, because air is about 78 % nitrogen. So to move out the equivalent of 1.5 % oxygen (the difference between 21 % and 19.5 %), the CO2 must also move out 4.5 % of the nitrogen. So its about 6 % of the volume of the room. And all this assumes that the CO2 is completely mixed with the air.

    But, and see below, according to NIOSH (National Institute for Occupational Safety and Health), CO2 has lethal effects at a somewhat lower concentration than that – namely 4 %:

    NIOSH REL:
    5,000 ppm TWA
    30,000 ppm STEL
    40,000 ppm IDLH

    Current OSHA PEL:
    5,000 ppm TWA

    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).

    The IDLH of 40,000 ppm = 40,000/1,000,000 x 100 = 4%.



    I had some other posts on the subject see:

    ControlBooth > Special F/X > F/X Questions?
    Hazers vs. Dry Ice--Health Risk

    Joe
     
  15. MHSTech

    MHSTech Active Member

    Messages:
    138
    Likes Received:
    0
    Location:
    Ohio
    Current OSHA PEL:
    5,000 ppm TWA

    That's the little tidbit of info I couldn't find. Thanks for the correction.
     
  16. JahJahwarrior

    JahJahwarrior Active Member

    Messages:
    526
    Likes Received:
    1
    so....does anyone have any clue how to do this without buying aimable jets and stuff? I don't need anything DMX controlled.....20 feet of hosing that would direct the stuff (I know they make stainless steel braided covered hosing for paintball guns, but i have never seen it in 20 foot lengths) and a nozzle of some sort, and a valve thats easy to open and shut? How long will a bulk tank of the stuff last? Could I get a cool "puff" affect by venting quickly just say a 20 oz tank? I have access to a few of those.
     
  17. koncept

    koncept Active Member

    Messages:
    590
    Likes Received:
    3
    Location:
    .
    call a welding supply shop. they should be able to help you out
     
  18. MHSTech

    MHSTech Active Member

    Messages:
    138
    Likes Received:
    0
    Location:
    Ohio
    Depends what size of tank you get.

    Also, you should be able to get your C02 from whoever refills/recharges your fire extinguishers. And as for the 20 ft of whatever, you should be able to get away with using steel pipe...say 1/8" or 1/4"?

    If you just want to create a puff of C02, I don't know if you really need a nozzle. Maybe somebody else could answer this.
     
  19. JahJahwarrior

    JahJahwarrior Active Member

    Messages:
    526
    Likes Received:
    1
    well, not just a puff like a tiny cloud, but say I want to have co2 shoot 10 feet high for 10 seconds. I'm guessing I need to know how far to crack open the valve? And using pipe would be cumbersome, but doable. I wish someone on here had extensive expereience with this....I have not had much luck on google.........
     
  20. Mayhem

    Mayhem Senior Team Emeritus Premium Member

    Messages:
    1,790
    Likes Received:
    4
    Location:
    Australia
    Well without the extensive experience you are Googling for, ask yourself this question? How does a CO2 fire extinguisher work?

    Essentially, you are trying to reproduce a similar unit, although you wish to have a higher stream and that I suspect is going to be determined by pressure and nozzle size and shape.

    The long nozzle on the extinguisher is there to focus and concentrate the CO2 and your nozzle would be smaller than this. As I previously mentioned, the ones used by Motley Crue were only about 3 or 4 inches high and probably no more than 2 inches in diameter.

    The pipe is going to need to be at least a half inch in diameter I think and for R&D purposes, I would use a ballcock valve to gauge the flow rate required. Whilst I have never pulled an extinguisher apart, my guess is that it would open the valve fully.

    Pressure in the canister is also going to play a role in getting the desired effect and off the top of my head, I cannot recall what a CO2 extinguisher is set at. To be honest, I cannot even recall if it shows pressure or just a charge/good indicator.

    One problem you will probably encounter will be icing due to components getting too cold and this may be due to too small diameters or too high a flow rate or a combination of the two.

    I guess that you are going to do some experimentation with what you have lying around and what you can pull together.

    My advice is this:

    1. Speak to a local company that services fire extinguishers and ask them for their thoughts and comments on such a system. They should be able to help you with flow rates, diameters and the likes.

    2. Whatever you try out, make sure that you are protected and at the very least wearing safety glasses and a long sleeved top and jeans. This stuff can give a nasty burn and you sure as hell don’t want to get it in your eyes.

    3. The pressure could cause the nozzle and hose to fly about so make sure it is securely fastened.

    4. Test is in a well ventilated area and have someone with you in case you do get injured.

    5. Do not say “oh what the hell” and use a CO2 fire extinguisher as the FX. Fire extinguishers should be used for one thing only - Fighting fires. Now I know that several people will disagree with me and tell me they do it all the time. My reasoning is that should a fire break out and the extinguishers emptied to get a cool FX, I am not going to be a happy camper.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice