( ( ( A release ) ( of ( gaseous UF6 ) ) ) ( ( could ( occur ( only ( if ( there ( is ( ( ( a fire ) ( with ( ( sufficiently high ) ( ( temperature and ) duration ) ) ) ) ( to ( ( ( heat ( the ( solid UF6 ) ) ) ( to ( the point ) ) ) ( where ( it ( ( undergoes sublimation ) ( -LRB- ( ( ( ( change ( from ( a solid ) ) ) ( to ( a gas ) ) ) ( without ( ever ( becoming ( a liquid ) ) ) ) ) -RRB- ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT A) (NN release)) (PP (IN of) (NP (JJ gaseous) (NN UF6)))) (VP (MD could) (VP (VB occur) (SBAR (RB only) (IN if) (S (NP (EX there)) (VP (VBZ is) (NP (NP (DT a) (NN fire)) (PP (IN with) (NP (ADJP (RB sufficiently) (JJ high)) (NN temperature) (CC and) (NN duration))) (S (VP (TO to) (VP (VB heat) (NP (DT the) (JJ solid) (NN UF6)) (PP (TO to) (NP (DT the) (NN point))) (SBAR (WHADVP (WRB where)) (S (NP (PRP it)) (VP (VBZ undergoes) (FRAG (NP (NN sublimation))) (PRN (-LRB- -LRB-) (S (VP (VB change) (PP (IN from) (NP (DT a) (JJ solid))) (PP (TO to) (NP (DT a) (NN gas))) (PP (IN without) (S (ADVP (RB ever)) (VP (VBG becoming) (NP (DT a) (NN liquid))))))) (-RRB- -RRB-)))))))))))))) (. .)))
A release of gaseous UF6 could occur only if there is a fire with sufficiently high temperature and duration to heat the solid UF6 to the point where it undergoes sublimation (change from a solid to a gas without ever becoming a liquid).
(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.