[Jivemaster]

I'm looking at buying a couple of CQ2 jets for event hire with operator. Does anyone care to share any experiences?

[Madams]

Magic FX Co2 jets are quite good.

Link Here



Madams

[david.elsbury]

Well that's hardly sharing an experience is it...

[Jivemaster]

OK simple question; Is there any real evidence(HSE reports or the like) of CO2 jets causing significant gas displacement and any adverse reactions?

[Ashley R]

Well Co2 is heavier than air, and does love to collect in low lying area's such as Orchestra pits. Then it would be possibly advisable to install a CO2 meter in these low lying area's to ensure that there are no dangerous levels building up in these areas.

[Brian]

Not of CO2 jets although there has been some work on deaths attributed to CO2 fire suppression systems. There are some links on the Wikipedia page for Carbon Dioxide.

As an exercise it's quite easy to work out how much you raise the CO2 level in a space when using them.

Knowns are...

Usual level of CO2 in air
Maximum amount of CO2 used in a show
Danger levels for CO2 in air
Volume of space

ie 45kg of CO2 (= large cylinder) will raise the level to 1% (=some people drowsy) in a space of approx 4,000 cubic m.

4,000m3 is a room 4m high by 30m wide by 30m long (=smallish event space)


Another way of looking at it is to compare the additional CO2 to that produced by people breathing...

I've seen a figure of 5g/person/minute of exhaled CO2.

So, 45kg of additional CO2 is the same as that produced by 150 people in one hour. Is that a problem?

[ramdram]

Interesting side issue of where the CO2 goes. If we were to assume that the CO2 collected, over time, in the basements and understage spaces of theatres, and other places generally, then we would know by the numbers of dead people. However the CO2 must "escape" somehow despite it being one of the heavier components of air.

I suppose as has been alluded to above it depends on the speed of saturation of CO2 into a space. But, when you consider the orchestra are creating CO2 much more rapidly than a person sitting and not doing much in the way of activity then there does not seem to be that much of a worry. Plus there may be a constant flow of CO2 into the orchestra pit(s) from auditoria the world over and nobody has remarked thus before now. Some older theatres may not have had air handling facilities in the days of yore anyway.

It might be worth noting that when giving mouth to mouth/nose resuscitation the recipient is receiving a higher dose of CO2 anyway cf the normal amount by virtue of said air being "secondhand" so to speak.

That said I gather that the CO2 in the body is necessary to invoke the breathing in part of the respiratory cycle.

If it was that dangerous I am sure "we" would have noticed by now and all spaces below ground in a theatre would be vented, with all access being denied if the vent fans packed in.

[Jivemaster]

So in reality there is a risk of increasing the partial pressure of CO2 but no-one has yet experienced ill effects or seen it reported.

I've seen podium dancers with smaller CO2 cylinders in a Scuba type backpack, with CO2 Lances like a pressure washer jet, Any wisdom to share?

[Superpants]

The difference with groups such as orchestras is that the CO2 will be already well mixed with other gases (nitrogen, unused oxygen) as it's exhaled, and will be warm, so won't pool and sink in the same way that cold, pure CO2 will.

[kerry davies]

As long as the use is by experienced operators there should be no difficulty since they would automatically make a specific RA for each instance. Where it could go wrong, and why I am belt and braces on BR, is when inexperienced or unwary operators use them and circumstances combine negatively.

Why, am I so cautious, you ask? Unconsciousness is almost immediate and the best studies have been those around the Lake Nyos incident where an 8-10% concentration killed 1700 people. The gas killed all living things within a 15-mile radius of the lake.

Yes 150 people produce lots of CO2 over time but this sort of instantaneous raising of the concentration needs to be carefully judged.

Exhaled air during normal deep breathing contains 4% CO2 and mouth-to-mouth "panting" a lot closer to the ambient 0.4%. Increased CO2 in the bloodstream actually promotes deeper and heavier breathing so for resuscitation it is good. For higher concentrations it works the other way and you ingest even more as you get poisoned.

[ramdram]

Interesting info on the Lake Nyos incident, and 8/10% concentration of CO2 is massive when you think O2 is around 20%.

However IF this issue of CO2 in orchestra pits was that dangerous then we would all know about it. The gas must escape or it would cool off and sink into the lower basements. I recall Brian(?) posting some snaps of a CO2 "curtain" or fog coming off an LX bar or similar in a club yet nobody died.

Possibly the fact the air handling kit changed the air fast enough to prevent the saturation becoming to great too quickly. Brian mentioned the figures above producing a saturation of 1% and I presume that would be a "static" volume. Presumably in a real world situation the doors would be opening almost non stop and the ac working continuously.

Presumably the kit comes with method statements and similar so there would be caveats in abundance?

(In any event (groan) I can think of far worse (if not exactly lethal) gases emanating from an assembled host of 150 Sweaty Betties...)

[slipstream]

We had and then ditched 4 heads of the generic chinese static jets - we found the effect was decent but the co2 consumption is huge - think of a large bottle lasting about 2 mins per head the hoses are pricey and fragile when moved cold, the bottles are 105kg each - so your moving 1.2 ton to do 3 bottles worth in 4 heads for a gig with a cost per bottle around £35 - depends on your market but too steep for many of the local jobs paying for gas and crew to shift and run it - co2 RA is not onerous unless your in a tiny sealed venue.

Sam

This post has been edited by slipstream: 14 August 2012 - 10:25 PM