Acetylene is not especially toxic, but when generated from calcium carbide, it can contain toxic impurities such as traces of phosphine and arsine, which give it a distinct garlic-like smell. It is also highly flammable, as are most light hydrocarbons, hence its use in welding. Sep 24, 2018 · Arne Dedert/Getty Images If you've ever tried to ripen a piece of fruit by sticking it in a bag with a banana, you've harnessed the power of ethylene. Ethylene is an important plant hormone. In Jan 20, 2021 · Like methane, neither propane nor butane has an odor of its own. However, gas producers add the agent ethyl mercaptan to the gas mixture for safety purposes. This provides a recognizable scent, which will be familiar to anyone who has ever used a gas cylinder BBQ. EpmWv5t.