If you’re a little confused by this whole Volkswagen controversy, don’t worry, you’re not alone. For those of you out of the loop, the German car company recently admitted to using engine software to cheat diesel car emissions tests in the United States. Cheating on tests is never a good thing, but it’s downright criminal when that cheating endangers the lives of millions of people who are unknowingly exposed to 15 to 35 times the legal limit for poisonous nitrogen oxide (NOx).

Diesel engines, which tend be more popular in Europe as opposed to the U.S., produce a lot more NOx compared to petrol (gasoline) engines. According to the Environmental Protection Agency, diesel exhaust is a major contributing factor to air pollution with fine particles that can irritate asthma sufferers while causing serious lung damage. This is precisely why emissions testing exists. It’s also why Volkswagen worked so hard to avoid these safety restrictions.

Professor Martyn Poliakoff from Periodic Videos uses his knowledge of chemistry to help explain the science behind Volkswagen’s emission-rigging scandal.