( ( ( ( ( Ozone ( is ( made ( when ( ( a ( electric spark ) ) ( passes ( through air ) ) ) ) ) ) ) , ) and ) ( ( ( this accounts ) ( for ( the ( characteristic odor ) ) ) ) ( ( give off ) ( by ( some ( electrical motors ) ) ) ) ) ) . )
(ROOT (S (S (NP (NN Ozone)) (VP (VBZ is) (VP (VBN made) (SBAR (WHADVP (WRB when)) (S (NP (DT a) (JJ electric) (NN spark)) (VP (VBZ passes) (PP (IN through) (NP (NN air))))))))) (, ,) (CC and) (S (NP (NP (DT this) (NNS accounts)) (PP (IN for) (NP (DT the) (JJ characteristic) (NN odor)))) (VP (VBP give) (PRT (RP off)) (PP (IN by) (NP (DT some) (JJ electrical) (NNS motors))))) (. .)))
Ozone is made when a electric spark passes through air, and this accounts for the characteristic odor give off by some electrical motors.
(ROOT (S (NP (NN Ozone)) (VP (VBZ is) (NP (NP (DT a) (NN compound)) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (EX there)) (VP (VBZ is) (VP (VBG sparking) (NP (JJ electrical) (NN equipment))))))))) (. .)))