The gases usually found in sealed regions mainly contain methane, hydrogen, carbon monoxide, carbon dioxide, nitrogen, and oxygen.
(The gases; found; L:in sealed regions; T:usually) (The gases usually found in sealed regions; mainly contain; methane, hydrogen, carbon monoxide, carbon dioxide, nitrogen, and oxygen)
The gases The gases usually found in sealed regions
found mainly contain
L:in sealed regions T:usually
methane, hydrogen, carbon monoxide, carbon dioxide, nitrogen, and oxygen