Cov ntaub ntawv tseem ceeb yog cov pos hniav thiab cov hmoov txhuv nplej siab, uas yog du rau qhov kov thaum siv, nrog cov xim ci thiab tag nrho, hloov me ntsis hauv cov duab ntub dej thiab qhuav, tiaj tus thiab tsis yog curling, thiab tsis muaj formaldehyde.