In November of 1999, Andy McCoy of Virginia Tech was found dead of asphyxiation in his apartment. He had purchased nitrous oxide canisters and a cracker from a now defunct website. He had a plastic bag (over his head) tightly belted to his body. If you read the news report, note that they suggest [he] probably inhaled so much that he cut off his oxygen supply and suffocated.
In the former case, Lawrence Teiman, the website proprietor was convicted in Federal Court for the intent to mislead government officials because the nitrous oxide he sold wasn't adequately labeled with directions for use and warnings about the dangers of inhaling the gas. He was convicted to 15 months in prison and a $40k fine. This is a far cry from the 15 years and $1.25M that interstate marketing of a misbranded drug could bring.
There is a curious catch-22 here in that nitrous is not illegal to sell, only illegal to inhale. But if Teiman had included a sheet of more specific warnings, the Feds would have used this as evidence that he intended inhalation and he would have likely received a heavier sentence under the Interstate Commerce Act.
As a website not engaged in the business of selling nitrous, we have no such restrictions. PLEASE DO NOT PUT PLASTIC BAGS OVER YOUR HEAD.
A similar case was reported at MIT in 1999 involving a plastic bag over the head of Richard Guy. In the story linked, note that they refer to the death as a drug overdose. The parents subsequently filed a wrongful death suit against MIT, saying it should have taken stronger measures to keep students from stealing the gas from laboratories and that it should have been put on notice of illegal drug use by the condition of their son's dorm, where "the walls and ceilings of part of the 5th floor were painted black and light bulbs [were] painted pink and purple". The university subsequently settled out of court (2005/07/12). In the dorm there were also two students arraigned for intent to distribute (several types of drugs) but it is unclear what happened to the case.
At MIT there are several other citations of injury and death including releasing nitrous inside a van. (See above link.)
In Florida in 1998, a teenager died after hitting her head in a fall that was blamed on nitrous. Subsequently, raves in Tampa were banned.
In 2002, in New Haven CT, two hospital patients died after there was a mixup in the oxygen and nitrous lines.
In 2005, in Sydney AU, two people died after opening a tank in their car.