Peb yog cov khoom siv tu tsev tsim khoom ua ke kev tshawb fawb, kev tsim kho, tsim khoom, muag thiab kev pabcuam tomqab muag. Peb cov khoom tseem ceeb muaj xws li cov tshuab nqus tsev vacuum, tawg-pov thawj lub tshuab nqus tsev, lub tshuab nqus tsev siab, hluav taws xob nqus tsev, ntub & qhuav nqus tsev thiab lwm yam.