Poison Gas

This would be short:

Today during chemistry pratical lesson, everything was going fine. I was doing my experiments quickly and the results were correct. Then 30 minutes before the class ended, the lecturer discuss the results with us. While discussing one particular experiment, he mentioned that Nitrogen monoxide gas would be released. Nitrogen monoxide is a brown gas and is very poisonous. Imagine the surprised as we did the experiment without seeing the brown gas so that means most of us actually were poisoned by the gas. I was one of them. Luckily, nothing happened at all since we might had breath in just a tiny amount of the gas.