( ( At ( this ( temperature ( and ( oxygen level ) ) ) ) ) ( , ( ( ( ( ( ( the ( combustible solids ) ) , ) liquids ) and ) sludge ) ( ( convert ( into ( a gas ) ) ) . ) ) ) )
(ROOT (S (PP (IN At) (NP (DT this) (NN temperature) (CC and) (NN oxygen) (NN level))) (, ,) (NP (NP (DT the) (JJ combustible) (NNS solids)) (, ,) (NP (NNS liquids)) (CC and) (NP (NN sludge))) (VP (VBP convert) (PP (IN into) (NP (DT a) (NN gas)))) (. .)))
At this temperature and oxygen level, the combustible solids, liquids and sludge convert into a gas.
(ROOT (S (NP (NNS Gases) (CC and) (NNS liquids)) (VP (VBP become) (NP (NNS solids)) (PP (IN at) (NP (JJ low) (NNS temperatures)))) (. .)))
Gases and liquids become solids at low temperatures.