Thaum ua haujlwm, kaw ob pawg ntawm kev kuaj xyuas li qub thiab sib npaug li qub.Yog tias xav tau kev tshuaj xyuas, tsuas yog txiav tawm lub siab siab thiab qis qis, qhib qhov sib npaug valve thiab ob daim tshev li qub, thiab tom qab ntawd kaw qhov nyiaj tshuav valve kom ntsuas thiab sib npaug ntawm cov khoom xa tawm.