ɪn pˈɑːɹɾɪkəl fˈɪzɪks, ɐ hɜːmˈɛɾɪk dɪtˈɛktɚ ˈɔːlsoʊ kˈɔːld ɐ fˈoːɹ pˈaɪ dɪtˈɛktɚ ɪz ɐ pˈɑːɹɾɪkəl dɪtˈɛktɚ dɪzˈaɪnd tʊ əbzˈɜːv ˈɔːl pˈɑːsᵻbəl dᵻkˈeɪ pɹˈɑːdʌkts əvən ˌɪntɚɹˈækʃən bᵻtwˌiːn sˌʌbɐtˈɑːmɪk pˈɑːɹɾɪkəlz ɪn ɐ kəlˈaɪdɚ baɪ kˈʌvɚɹɪŋ æz lˈɑːɹdʒ ɐn ˈɛɹiə ɚɹˈaʊnd ðɪ ˌɪntɚɹˈækʃən pˈɔɪnt æz pˈɑːsᵻbəl ænd ɪŋkˈoːɹpɚɹˌeɪɾɪŋ mˌʌltɪpəl tˈaɪps ʌv sˈʌbdɪtˈɛktɚz.
In particle physics, a hermetic detector (also called a 4π detector) is a particle detector designed to observe all possible decay products of an interaction between subatomic particles in a collider by covering as large an area around the interaction point as possible and incorporating multiple types of sub-detectors.