We all know that helium makes your voice all squeaky like a chipmunk, but in the last few years, there's been a new voice-altering gas on the block. It's an ultra-dense substance called sulfur hexafluoride, and it makes your voice go all deep and demony.
The science behind this is actually really cool. When lighter-than-air helium enters your vocal tract, it's not the vibration rate of your vocal cords that changes; rather it's the speed of the sound waves travelling through the less dense helium. This speedy sound waves make your voice all squeaky.
Sulfur hexafluoride (SF6) has the opposite effect. Those sound waves slow down, which lowers your voice. This effect - which is pretty funny - has done the TV talk show rounds.
Because the gas is so dense - it's about five times the density of air - it behaves a little bit like liquid. You can put it in a tank and it will - unless there are air disturbances - stay put.
You can also, as demonstrated in a Nickipedia video from a year ago, which is now doing the rounds again thanks to a reddit post, use it to extinguish flames, since it displaces the oxygen the flames need to survive.
This looks really, really cool - and it's also, how can we put this, absolutely freaking terrible for the environment. This is because SF6 is actually the most potent greenhouse gas that has ever been evaluated by the Intergovernmental Panel on Climate Change.
It has a global warming potential around 22,800 times that of carbon dioxide over 100 years. In other words, 1 kilogram of SF6 is equivalent to 22.8 tonnes of CO2.
It gets worse. Once it's in the atmosphere, it can stay there for up to 3,200 years. And it's not like you can just scoop the gas back up once you've released it.
It's most commonly used in the electrical industry to quench electrical discharges and therefore prevent fires. And, according to gas industry publication Gasworld, although such usage is regulated, it still gets into the atmosphere.
"As recently as 2002," the SF6 Gasworld factsheet reads, "industry released 600 metric tons of SF6 into the atmosphere – the equivalent of 3,103,896 passenger cars driven for a year, or the burning of 72,866 railcars of coal."
The size of the tub used in the video is not revealed, but it does look to be at least 30 litres (8 gallons), and presenter Nick Uhas fills it almost right to the top.
According to the above figures, and bearing in mind that this is just an estimate, a full 30-litre box of sulphur hexafluoride would contain around 195 grams of the substance. That's equivalent to 4.4 tonnes (or metric tons) of CO2.
A passenger vehicle, according to the EPA, emits around 4.6 tonnes of CO2 every year. Yeah.
So while putting out a bunch of tea light candles with a tub of SF6 looks really awesome (and it really does), next time you think of a cool idea for a video, back away from the chemistry supplies website and do a bit of research in case you accidentally wreck the environment.