Explain Like I'm Five | Don't Panic!
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ELI5: How can they cool a concert instantly? (self.explainlikeimfive)
submitted 8h ago by seattlesweiss
Once, I went to a concert and it was super hot inside. Then they sprayed some kind of gas or something from the stage, and the entire hall cooled down *almost instantly*. How is that possible?
The sprays looked similar to when I turn a duster can upside down, but I know that stuff is toxic so there's no way they were using that. Right?
The sprays looked similar to when I turn a duster can upside down, but I know that stuff is toxic so there's no way they were using that. Right?
CupcakeValkyrie 1 points 8h ago
They probably sprayed cool water into the air. When you spray a fine mist of cool water vapor into hot air, it evaporates almost immediately, and in doing so it draws heat from the air, which rapidly cools it. It's the same principle used for an evaporative cooler.
FD4L 1 points 1h ago
We use that principal in firefighting. Turbulent gas layers overhead can become superheated and dangerous, so we often adjust our nozzles to a narrow fog pattern and blast a few shots into the ceiling, so that the hot gasses absorb the fine droplets and cool down. It delays the possibility of rollover burns and allows us to keep moving as we look for the seat of the fire.
Otherwisuhii 1 points 21m ago
They are used for instant fog effects on stage, but in a sufficiently small venue
Nationalook401 1 points 10m ago
10/10
collude 1 points 7m ago
We've moved away from this tactic at my department. We just direct a straight stream at the ceiling until the conditions permit advancing forward.
-LsDmThC- 1 points 7h ago
That principle is just called evaporative cooling
JustnInternetComment 1 points 1h ago
Like an evaporative cooler?
Complexity_OH 1 points 42m ago
Its actually Co2, same stuff restaurant uses to carbonate the soft drinks. Concerts use this as a safe and impactful special effect. It makes a white cloud of cold fog and is harmless in short durations.
theposition5 1 points 37m ago
Is that not dangerous to electronics?
Riegel_Haribo 1 points 6h ago
This is likely the kind of fogger that was being used:
https://www.smokemachines.net/buy-liquid-nitrogen-cannon.shtml
https://www.smokemachines.net/buy-liquid-nitrogen-cannon.shtml
Chromotron 1 points 4h ago
>A loud roar also accompanies the effect as the system blasts up to 50 litres of liquid nitrogen per second into the atmosphere.
That's 35 m³ of nitrogen gas. Sounds like it is just nitrogen asphyxiation waiting to happen if some nightclub owner completely overuses this kind of thing in too small an enclosure.
That's 35 m³ of nitrogen gas. Sounds like it is just nitrogen asphyxiation waiting to happen if some nightclub owner completely overuses this kind of thing in too small an enclosure.
Riegel_Haribo 1 points 4h ago
Yep, with a $50000+ system like that, they also have oxygen monitors or limiters of how often it can be used.
The effect is not because of the amount of nitrogen being used, but because of the cooling effect and condensation it has on water vapor.
Also, you don't want to make patrons feel more tired.
The effect is not because of the amount of nitrogen being used, but because of the cooling effect and condensation it has on water vapor.
Also, you don't want to make patrons feel more tired.
JoushMark 1 points 4h ago
They can use liquid air at 80/20 nitrogen to oxygen and avoid that problem.
Chromotron 1 points 3h ago
That has other hazards, liquid oxygen is its own beast, even if diluted with nitrogen. But they use pure N2 anyway, according to their website.
As long as it gets continuously monitored and there is good ventilation, using this system is safe. But I expect some nightclub owner to have no clue.
As long as it gets continuously monitored and there is good ventilation, using this system is safe. But I expect some nightclub owner to have no clue.
primalmaximus 1 points 57m ago
Yep. Liquid oxygen is a very dangerous fire hazard.
giggling_hero 1 points 4h ago
The other answers are incorrect, it’s liquid delivery cO2 through a solenoid. I do this for a living.
Zouden 1 points 2h ago
Liquid CO2?
BOW57 1 points 2h ago
Can you elaborate? Enough liquid CO2 in a huge room full of people to cool it down substantially sounds like a great way to reduce the oxygen percentage.
Martian8 1 points 1h ago
If you’re using liquid CO2 then you can utilise the Latent vaporisation energy. Basically, it takes a lot of energy to change a liquid to a gas, so you don’t actually need that much CO2 to provide a large amount of cooling.
In addition, assuming the CO2 is very cold, you’re warming it up by a lager amount (maybe around 100 degrees). You only need to cool the room a little - at a guess, no more than 10 degrees. So you have a lot of ‘stored cold’ in the cold CO2 that can be used to cool the room only a little.
Both of these factors mean you probably don’t need that much liquid CO2 to cool a room.
But that’s all guess work, I don’t actually know what the required amount it. Assuming my the person above is correct, it’s clearly not a harmful amount.
In addition, assuming the CO2 is very cold, you’re warming it up by a lager amount (maybe around 100 degrees). You only need to cool the room a little - at a guess, no more than 10 degrees. So you have a lot of ‘stored cold’ in the cold CO2 that can be used to cool the room only a little.
Both of these factors mean you probably don’t need that much liquid CO2 to cool a room.
But that’s all guess work, I don’t actually know what the required amount it. Assuming my the person above is correct, it’s clearly not a harmful amount.
Madgyver 1 points 48m ago
>a great way to reduce the oxygen percentage.
Not that important. Raising the CO2 is way more dangerous.
Not that important. Raising the CO2 is way more dangerous.
propargyl 1 points 2h ago
Carbon dioxide is one of the most powerful stimulants of breathing.
m0le 1 points 2h ago
Sort of, but it does it by making you think you're suffocating so you start to hyperventilate. That doesn't sound like fun in a nightclub...
propargyl 1 points 1h ago
>Carbon dioxide is one of the most powerful stimulants of breathing.
The powerful stimulation of ventilation by carbon dioxide inhalation and the near-constancy of arterial PCO2 during rest and exercise indicate the importance of CO2/H+ receptors in the regulation of breathing. There are both peripheral and central chemoreceptors with the central ones accounting for about 70% of the CO2 effect. These sensors operate in feedback control systems that help maintain levels of CO2 in the body within narrow limits.
The powerful stimulation of ventilation by carbon dioxide inhalation and the near-constancy of arterial PCO2 during rest and exercise indicate the importance of CO2/H+ receptors in the regulation of breathing. There are both peripheral and central chemoreceptors with the central ones accounting for about 70% of the CO2 effect. These sensors operate in feedback control systems that help maintain levels of CO2 in the body within narrow limits.
greatwhitekitten 1 points 41m ago
Get this to the top it’s the one. They do this at raves all the time.
juliet_delta 1 points 38m ago
Cryo cannons is correct! They are used for instant fog effects on stage, but in a sufficiently small venue, you will feel the chilling effects of the phase change of the gas. It's not meant to cool you down, it's just meant to look cool. I recently experienced this at a Memphis May Fire concert. It felt great.
Warmstar219 1 points 7h ago
It's possible that it was compressed air. The vaporization and expansion of a gas sucks up a lot of energy, which is why compressed air cans (not usually actual air) get very cold when used.
JoushMark 1 points 3h ago
The stuff in a duster can doesn't have to be toxic. The basic propellant is butane and it's relatively nontoxic, but people abuse it as a way to get high so they add bitterants.
It's not butane though because you wouldn't pump a bunch of that into a venue. It's not toxic at reasonable dosages, but it's wildly flammable.
Any liquid vaporizing absorbs energy to change state. For cheap and safe cooling liquid nitrogen could be used, or liquid nitrogen mixed with liquid oxygen to assure you aren't accidently lowering the oxygen in the immediate area too much. You'd see a lot of white 'fog' in this case, as the rapid cooling condenses water out of the air.
It's not butane though because you wouldn't pump a bunch of that into a venue. It's not toxic at reasonable dosages, but it's wildly flammable.
Any liquid vaporizing absorbs energy to change state. For cheap and safe cooling liquid nitrogen could be used, or liquid nitrogen mixed with liquid oxygen to assure you aren't accidently lowering the oxygen in the immediate area too much. You'd see a lot of white 'fog' in this case, as the rapid cooling condenses water out of the air.
Admirable-Shift-632 1 points 6m ago
That’s literally rocket science on an ELI5 post 😂
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