Assertion: methane's concentration | /r/Causes | suffocation
Facets:
value: in the presence of sufficient oxygen
type: OTHER
Source sentences:
text: Concentrations of 7% to 10% (70,000 to 100,000 ppm) may cause suffocation, even in the presence of sufficient oxygen, manifesting as dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour.