Ah, the modern world.
Sure, we don't get any concrete clues about the world our speaker inhabits – there aren't descriptions of parking lots or big box stores or that wonder of the modern world, McDonald's. Still, we're fairly confident that this poem is set in the 20th century. For one thing, acid and gas weren't all that available until the 20th century.
More importantly, though, the sort of easy contemplation of the value of suicide wouldn't have been something that people in the 1800s would have considered polite conversation. That leaves us with the 20th century – a time when individuals became more and more in control of their environments and, paradoxically, more and more isolated from one another. In other words, this poem showcases all the ways that humans can manipulate the things around them…even if only to end their own lives.