A years old waste decomposes, it produces flammable and toxic gases.

一年的废物分解，它产生易燃和有毒气体。

Syrian activist groups say helicopters dropped bombs containing a toxic gas on a rebel-held city named Douma.

叙利亚激进组织说，直升机向反对派控制的城市杜马投掷了含有有毒气体的炸弹。

That`s a toxic gas which comes from vehicle exhaust.

那是一种来自汽车尾气的有毒气体。

It's also known as " the poison plastic" because, when it's melted, it can release a corrosive and toxic gas called, yeah, hydrochloric acid.

它也被称为有毒塑料，因为当它熔化时，是释放一种腐蚀性的有毒气体，叫做盐酸。