<prompt> Translate the following text to EnglishIkiwa haijaanza hewa wakati wa masaa nane ya kwanza ya mtihani, DO inaweza kutolewa wakati wa kipindi kisicho na usimamizi, na hivyo kufuta mtihani.  <response>: Unless aeration is initiated during the first 8 h of the test, the DO may be exhausted during an unattended period, thereby invalidating the test. 