Fans pointed out: “During the final scene of this episode, Sheldon steps out of his office wearing a gas mask.
“He engages Leonard in conversation where he then states he is making hydrogen sulphide gas (more commonly known as H2S). Leonard correctly identifies this as highly flammable.”
But this was not all the gas could have done, as they added: “However, this gas is far more dangerous and is harmful to the human body at as low a concentration as 20 parts per million (ppm), can cause permanent damage at 100ppm and is fatal after two breaths at 500ppm.”
The Big Bang Theory is available to stream on Netflix UK now.