Low Fogger

[livelifetotheverymax]

Hey, as part of an opera we're putting on at Uni next term we're wanting to have a low fog effect. Unfortunately dry ice is out of the question because of all the health and safety aspects of using it with mostly inexperienced crew (that and an orchestra pit directly in front of the stage...)

 

I was wondering if anyone has any recommendations for low fog machines we could hire on a fairly limited budget and companies in the Yorkshire area that have hire stock.

 

Cheers, John.

[Ynot]

Hey, as part of an opera we're putting on at Uni next term we're wanting to have a low fog effect. Unfortunately dry ice is out of the question because of all the health and safety aspects of using it with mostly inexperienced crew (that and an orchestra pit directly in front of the stage...)

 

I was wondering if anyone has any recommendations for low fog machines we could hire on a fairly limited budget and companies in the Yorkshire area that have hire stock.

I'd look again at dry ice, as the H & S aspects are not as bad as you may think. Yes you need to know how to use it properly and safely, but it's by FAR a better effect.

 

Low fog, IMHO, has a great deal of drawbacks, as has been said here before.

[livelifetotheverymax]

I'd look again at dry ice, as the H & S aspects are not as bad as you may think.

 

The issue I have is that there's a 28 piece orchestra directly in front of the stage with the stage being just over 3.5' above floor level. I'm assuming this would cause issues with using dry ice, however I don't have experience of using it other than chucking a few hundred grams of it into a bowl of hot water in the kitchen. I've been doing a fair bit of reading about storage & usage etc around on here and elsewhere.

 

Cheers, John.

[Ynot]

That sort of situation crops up all the time for the simple reason that orchestra pits are where orchestra pits usually are.

And shows have used CO2 for years.

 

You may well need to look at a way of dissipating the fog when it drops, but to be honest it doesn't last that long and the heat in a pit will add to that dissipation.

[livelifetotheverymax]

That sort of situation crops up all the time for the simple reason that orchestra pits are where orchestra pits usually are.

And shows have used CO2 for years.

 

You may well need to look at a way of dissipating the fog when it drops, but to be honest it doesn't last that long and the heat in a pit will add to that dissipation.

Hmm, the radiators being at the front of the stage may help with this. I may have to look into this. Is there any way to check if the concentration of CO2 is too much or is it a bit more guesswork?

 

Cheers, John.

[slipstream]

NIOSH CO2 exposure limits: NIOSH recommends a maximum concentration of carbon dioxide of 10,000 ppm or 1% (for the workplace, for a 10-hr work shift with a ceiling of 3.0% or 30,000 ppm for any 10-minute period). These are the highest threshold limit value (TLV) and permissible exposure limit (PEL) assigned to any material.

 

OSHA CO2 exposure limits: OSHA recommends a lowest oxygen concentration of 19.5% in the work place for a full work-shift exposure. As we calculated above, for the indoor workplace oxygen level to reach 19.5% (down from its normal 20.9% oxygen level in outdoor air) by displacement of oxygen by CO2, that is, to reduce the oxygen level by about 6%, the CO2 or carbon dioxide level would have to increase to about 1.4% 14,000 ppm.

 

In summary, OSHA, NIOSH, and ACGIH occupational exposure standards are 0.5% CO2 (5,000 ppm) averaged over a 40 hour week, 3% (3,000 ppm) average for a short-term (15 minute) exposure we discuss and define short term exposure limits STEL below, and 4% (40,000 ppm) as the maximum instantaneous limit considered immediately dangerous to life and health. All three of these exposure limit conditions must be satisfied, always and together.

 

 

 

A hall 20 x 30 x 6m contains 3,600,000 l of air of which 752,400l (20.9%) is oxygen and 1440l (0.04%) CO2.

 

10 kilos of dry ice adds 5500 cubic litres of co2 into the space which makes the total volume of the co2 in the room 6940 litres which is 0.2%

 

Oxygen levels also change and drop - which is actually the more dangerous scenario but in this instance only to 20.87% well above guidelines

 

Airchanges for theatres should be about 10 per hour ie in a perfect world reversing the co2 change in 6mins

 

Someone may want to check my figures its 1 am now

 

Sam

[GridGirl]

Dry ice is by far the best effect, as others before me have said, but if it's totally out of the question then the best low fog machines are the LeMaitre ones - the older version is the LSG and the newer one is the FreezeFog Pro. Special smoke fluid into a G300 or similar machine which is hooked up to a cooling device which uses liquid CO2 to chill the fog so that it rolls along the ground. Not as good as dry ice, but pretty effective. JustFX used to have an LSG and probably still do - it's four years since we hired it from them so I can't be 100% sure!

 

Personally I've used dry ice on a decent number of shows with an orchestra in the pit and have never had a problem - it dissipates quickly and the band members are usually tall enough that the dry ice may collect around their feet but isn't high enough to cause issues with breathing. Of course, all due care should be taken!

[livelifetotheverymax]

Sweet, cheers guys. Dry Ice it should be. It'll probably work out cheaper for us anyway because we can get the dry ice from uni daily (and even carry it across campus so no delivery cost :unsure:) for a good price.

 

RA Wise the things we need to cover seem to be: hot water, very cold dry ice, vented storage during the show, competent operator, adequate airflow to dissipate and possibly slip hazards on stage from condensate. Have I missed anything glaringly obvious?

 

Cheers, John.