7 ▁g / m ol ) ▁and ▁is ▁therefore ▁used ▁as ▁CO 2 ▁abs orb ent ▁in ▁space ▁fl ights ▁since ▁the ▁Apol lo ▁program ▁to ▁spare ▁weight ▁at ▁launch . ▁During ▁Apol lo ▁ 1 3 ▁flight , ▁the ▁crew ▁shelter ed ▁in ▁the ▁lun ar ▁module ▁started ▁suffering ▁from ▁high ▁CO 2 ▁levels ▁and ▁had ▁to ▁adapt ▁spare ▁abs orb ent ▁cart rid ges ▁from ▁the ▁Apol lo ▁caps ule ▁to ▁the ▁LE M ▁system . ▁ ▁Rec ent ▁generation ▁of ▁CO 2 ▁abs orb ents ▁have ▁been ▁developed ▁to ▁reduce ▁the ▁risk ▁of ▁formation ▁of ▁to xic ▁by - products ▁as ▁a ▁result ▁of ▁the ▁interaction ▁between ▁the ▁abs orb ent ▁and ▁in h aled ▁an est het ics . ▁Some ▁abs orb ents ▁made ▁from ▁l ith ium ▁hydro x ide ▁( Li OH ) ▁are ▁also ▁available ▁for ▁this ▁purpose . ▁ ▁Reb re ather ▁use ▁Ex h aled ▁gas ▁must ▁be ▁passed ▁through ▁a ▁carbon ▁dio x ide ▁scr ub ber ▁where ▁the ▁carbon ▁dio x ide ▁is ▁absor bed ▁before ▁the ▁gas ▁is ▁made ▁available ▁to ▁be ▁bre athed ▁again . ▁In ▁re bre athers ▁the ▁scr ub ber ▁is ▁a ▁part ▁of ▁the ▁breath ing ▁loop . ▁Color ▁indicating ▁d ye ▁was ▁removed ▁from ▁US ▁Navy ▁fleet ▁use ▁in ▁ 1 9 9 6 ▁when ▁it ▁was ▁sus pected ▁of ▁re le asing ▁chemical s ▁into ▁the ▁circuit . ▁In ▁larger ▁environments , ▁such ▁as ▁recom pression ▁ch amb ers ▁or ▁sub mar ines ,