To answer the first part of your question, I'd like to say that our studies were very extensive.
你问题的第一部分,我要说的就是我们的研究非常广泛。
It must have been a gas that could burn but that would not explode, a gas that did not smell strong, and a gas that did not kill people.
它一定是一种能够燃烧而不能爆炸的气体,一种味道不很强的而且不使人致死的气体。