SPF 30 lossis siab dua yuav tsum tau siv los tiv thaiv UV rays los ntawm kev puas hlwb ntawm daim tawv nqaij. Qhov no yog cov nyiaj uas tau pom zoo los tiv thaiv kev mob qog noj ntshav ntawm daim tawv nqaij. Cov tshuaj pleev thaiv hnub yuav tsum tau siv kom huv si thiab rov siv dua thaum nruab hnub, tshwj xeeb tshaj yog tom qab nyob hauv dej. Kev saib xyuas tshwj xeeb yuav tsum tau them rau thaj chaw xws li pob ntseg thiab qhov ntswg, uas yog cov pob qog nqaij hlav cancer ntawm daim tawv nqaij. Cov kws kho mob dermatologist tuaj yeem tuaj yeem qhia txog yam tshuaj pleev thaiv hnub zoo tshaj plaws los siv rau cov tawv nqaij tshwj xeeb.
Cov koob tshuaj uas siv hauv FDA tshuaj pleev thaiv hnub yog 2 mg / cm2 ntawm cov tawv nqaij raug. Yog hais tias ib tug "nruab nrab" cov neeg laus tsim qhov siab 5 ft 4 nyob rau hauv (163 cm) thiab hnyav 150 lb (68 kg) nrog ib tug 32-inch (82-}cm) duav, tus neeg laus hnav da dej Kev hnav khaub ncaws npog lub puab tsaig yuav tsum siv li 30 g (los yog 30 ml, kwv yees li 1 oz) sib npaug rau thaj tsam ntawm lub cev. Qhov no tuaj yeem xav tau yooj yim dua li "pob golf" loj npaum li cas ntawm cov khoom hauv ib lub cev, lossis tsawg kawg yog rau teaspoonfuls. Cov neeg loj dua lossis me dua yuav tsum ntsuas cov khoom kom haum. Xav txog tsuas yog lub ntsej muag, qhov no txhais tau li ntawm 1/4 mus rau 1/3 ntawm ib qho teaspoon rau nruab nrab cov neeg laus lub ntsej muag.
Qee cov kev tshawb fawb tau pom tias tib neeg feem ntau siv tsuas yog 1/4 rau 1/2 ntawm cov nyiaj tau pom zoo kom ua tiav cov txiaj ntsig tiv thaiv hnub ci (SPF), thiab vim li ntawd qhov txiaj ntsig zoo ntawm SPF yuav tsum tau txo qis mus rau 4 lub hauv paus lossis ib lub hauv paus square. advertised tus nqi, feem. Ib txoj kev tshawb fawb tom qab pom muaj qhov sib txawv ntawm qhov tseem ceeb ntawm SPF thiab cov tshuaj pleev thaiv hnub siv, thiab cov txiaj ntsig tau ze rau linearity tshaj qhov xav tau los ntawm txoj kev xav.