Hello, I hope I can rely on you to tell me if an idea like this has been suggested before, and whether it is any good. Here's a quick brief.
SCP-1217 is a grey bath mat with unusual absorption properties. It is capable of sucking moisture from the air, and any objects around it at a steadily increasing rate. SCP-1217 was discovered after the ashes of a young woman were found resting on the mat in her bathroom. County police officers and forensic scientists reported an increase in body temperature, exhaustion, difficulty in breathing and migraines upon entering the room. At this point a group of level 3 agents were dispatched to investigate the death of the woman and quickly learned (after an agent unwittingly touched the mat and his finger disintegrated) that the mat was indeed the killer. The county law enforcement were informed that the victim had died of spontaneous human combustion.
The containment area of SCP-1217 would be a one metre by one metre and 30cm high vacuum sealed box, with walls made of steel 5cm thick.
That's not word for word what I would write, it's just a summary.