( Operators ( ( need ( to ( ( ( ( use ( a ( gas scrubber ) ) ) ( to ( remove ( acid-forming gases ) ) ) ) , ) ( assuming ( ( the material ) ( contained ( acid-forming elements ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Operators)) (VP (VBP need) (S (VP (TO to) (VP (VB use) (NP (DT a) (NN gas) (NN scrubber)) (S (VP (TO to) (VP (VB remove) (NP (JJ acid-forming) (NNS gases))))) (, ,) (S (VP (VBG assuming) (NP (NP (DT the) (NN material)) (VP (VBN contained) (NP (JJ acid-forming) (NNS elements)))))))))) (. .)))
Operators need to use a gas scrubber to remove acid-forming gases, assuming the material contained acid-forming elements.
(ROOT (S (NP (DT A) (NN gas)) (VP (VBZ assumes) (NP (NP (DT the) (NN shape)) (PP (IN of) (NP (PRP$ its) (NN container))))) (. .)))