Victorian toilets sometimes became stinky deathtraps. This video explains why—and be warned, it's a bit graphic. If one decided to light a cigarette or candle while on or near one of these 19th-century thrones, the results could be catastrophic.
Unlike modern toilets, where waste is flushed away, the waste stored beneath toilets in the Victorian era produced a buildup of flammable gas. This would travel up the pipes and into rooms. All it would take to trigger an explosion was a single spark or open flame.
Victorian homes contained a lot of dangerous obstacles that could lead to death: arsenic in the wallpaper, gaslight leaks, flammable lace curtains near the hearth, coal dust, chamber pots on attic ledges, bell-pull cords hungry for toddler necks, spontaneously combusting varnished furniture, lead in the drinking water, lung-collapsing corsets, experimental soap, cocaine for breakfast, phosphorous matches, chimney sweeps decomposing in the flues, ceramic hot water bottles cracking, haunted mirrors, etc., but this has to be the grossest. Thank goodness toilets have been updated, because this sounds like a pretty embarrassing way to go out.
See also: Patented tube for breathing air from behind toilet bend during a fire