The British red-top papers are in a bit of a tizz about nitrous oxide.
The drug has become known in the media (and nowhere else) as "hippy crack", and there are dire warnings in the papers about the risks of taking it.
It's nothing new - the drug has been a feature of clubs and festivals for years. The Home Office estimates that about 400,000 people in England and Wales take it each year.
No drug is completely safe. But nitrous is safer than most. Compare it to some other drugs. For instance, cocaine.
We could put it in a bit more context, and compare it to tobacco.
The papers claim to be worried about the Liverpool footballer Raheem Sterling, who was recently photographed apparently taking it. But he's about six times as likely to die playing football as he is taking nitrous oxide.
Again, this doesn't mean that it is safe. Depending on how it is taken, it can be harmful.
But put it this way: the average user would have to take nitrous oxide for 400,000 years to give them a 50% chance of dying.
If you want the maths, the probability of not dying in any given year is 100,000 - 0.17, or 0.9999983. If you multiply 0.9999983 by itself, you get the probability of dying in any given two years. If you multiply it by itself twice, three years. You have to multiply it by itself 400,000 times to get a figure of 0.507.