sˈʌtʃ dɪtˈɛktɚz ɑːɹ kˈɔːld "hɜːmˈɛɾɪk" bɪkˈʌz ðeɪ ɑːɹ kənstɹˈʌktᵻd sˌoʊ æz ðə mˈoʊʃən ʌv pˈɑːɹɾɪkəlz ɑːɹ sˈiːst æt ðə bˈaʊndɚɹiz ʌvðə tʃˈeɪmbɚ wɪðˌaʊt ˌɛni mˈuːvɪŋ bᵻjˌɔnd dˈuː tə ðə sˈiːlz; ðə nˈeɪm "fˈoːɹ pˈaɪ dɪtˈɛktɚ" kˈʌmz fɹʌmðə fˈækt ðæt sˈʌtʃ dɪtˈɛktɚz ɑːɹ dɪzˈaɪnd tə kˈʌvɚ nˌɪɹli ˈɔːl ʌvðə fˈoːɹ pˈaɪ stəɹˈeɪdiənz ʌv sˈɑːlɪd ˈæŋɡəl ɚɹˈaʊnd ðɪ ˌɪntɚɹˈækʃən pˈɔɪnt; ɪn tˈɜːmz ʌvðə stˈændɚd koʊˈɔːɹdᵻnət sˈɪstəm jˈuːzd ɪn kəlˈaɪdɚ fˈɪzɪks, ðɪs ɪz ɪkwˈɪvələnt tə kˈʌvɚɹɪdʒ ʌvðɪ ɛntˈaɪɚ ɹˈeɪndʒ ʌv ˈæzɪmˌʌθəl ˈæŋɡəl ænd sˌuːdoʊɹɐpˈɪdᵻɾi.
Such detectors are called "hermetic" because they are constructed  so as the motion of  particles are ceased at the boundaries of the chamber without any moving beyond due to the seals; the name "4π detector" comes from the fact that such detectors are designed to cover nearly all of the 4π steradians of solid angle around the interaction point; in terms of the standard coordinate system used in collider physics, this is equivalent to coverage of the entire range of azimuthal angle () and pseudorapidity ().